.rs .\" Troff code generated by TPS Convert from ITU Original Files .\" Not Copyright ( c) 1991 .\" .\" Assumes tbl, eqn, MS macros, and lots of luck. .TA 1c 2c 3c 4c 5c 6c 7c 8c .ds CH .ds CF .EQ delim @@ .EN .nr LL 40.5P .nr ll 40.5P .nr HM 3P .nr FM 6P .nr PO 4P .nr PD 9p .po 4P .rs \v | 5i' .sp 1P .ce 1000 \v'12P' \s12PART\ I \v'4P' .RT .ce 0 .sp 1P .ce 1000 \fBRecommendations G.211 to G.544\fR \v'2P' .EF '% \ \ \ ^'' .OF ''' \ \ \ ^ %' .ce 0 .sp 1P .ce 1000 \fBLINE\ TRANSMISSION\fR \v'2P' .ce 0 .sp 1P .ce 1000 INTERNATIONAL\ ANALOGUE\ CARRIER\ SYSTEMS .ce 0 .sp 1P .LP .rs .sp 26P .LP .bp .LP .rs .sp 10P .LP \fBMONTAGE:\ \fR PAGE 2 = PAGE BLANCHE .sp 1P .RT .LP .bp .sp 1P .ce 1000 \v'3P' SECTION\ 2 .ce 0 .sp 1P .ce 1000 \fBGENERAL\ CHARACTERISTICS\ COMMON\ TO\ ALL\fR .ce 0 .sp 1P .ce 1000 \fBANALOGUE\ CARRIER\(hyTRANSMISSION\ SYSTEMS\fR .ce 0 .sp 1P .IP \fB2.1\ Definitions and general considerations\fR .sp 1P .RT .sp 2P .LP \fBRecommendation\ G.211\fR .RT .sp 2P .ce 1000 \fBMAKE\(hyUP\ OF\ A\ CARRIER\ LINK\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.211'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.211 %' .ce 0 .sp 1P .ce 1000 \fI(amended at Geneva, 1964; further amended)\fR .sp 9p .RT .ce 0 .sp 1P .PP In the international telephone network, provision must be made for the interconnection of various sorts of carrier\(hytransmission systems using symmetric cable pairs, open\(hywire lines, coaxial cable pairs or radio\(hyrelay links. It is thus desirable for the carrier equipment used in these various systems, and which is not confined to a particular sort of line, to meet general CCITT recommendations. .sp 1P .RT .PP Basically, these equipments comprise translating equipments and through\(hyconnection filters. .sp 2P .LP \fB1\fR \fBTranslating equipments\fR .sp 1P .RT .PP These equipments are classified below according to the procedure used to make up the large\(hycapacity systems from the basic supergroup. .PP Two procedures are in use: .PP \fIProcedure\ 1:\fR \ the mastergroup and supermastergroup procedure; .PP \fIProcedure\ 2:\fR \ the 15\(hysupergroup assembly procedure; their use is described in the Recommendations concerning the various line systems. .PP For international links, procedure\ 2 can be used above 4\ MHz only by agreement between the Administrations concerned, including the agreement of the Administration(s) of the transit country or countries, if any. .PP In the Recommendations, the names of the equipments defined above are also used for equipments which translate a basic group, supergroup or mastergroup or a basic (No.\ 1) 15\(hysupergroup assembly into the line\(hyfrequency band and vice versa. .PP The translating equipments used in procedure\ 1 are: .RT .LP \(em channel\(hytranslating equipment, for translating the audio\(hyfrequency band into the basic group and vice versa (see Recommendations\ G.232, G.234\ [1] and\ G.235); .LP \(em group\(hytranslating equipment for translating five basic groups into the basic supergroup and vice versa; .LP \(em supergroup\(hytranslating equipment for translating five basic supergroups into the basic mastergroup and vice versa; .LP \(em mastergroup\(hytranslating equipment for translating three basic mastergroups into the basic supermastergroup and vice versa; .LP \(em supermastergroup\(hytranslating equipment for translating the basic supermastergroup into the line\(hyfrequency band and vice versa. .PP \fINote\fR \ \(em\ Figure\ 1/G.211, \fIa)\fR and \fIb)\fR recapitulates the basic frequency bands used in procedure\ 1; the through\(hyconnection possibilities described in Recommendation\ G.242 are provided for in these bands. .bp .LP .rs .sp 42P .ad r \fBFigure 1/G.211, p.\fR .sp 1P .RT .ad b .RT .PP The translating equipments used in procedure\ 2 are: .LP \(em channel\(hytranslating equipment and group\(hytranslating equipment, as defined for procedure\ 1; .LP \(em supergroup\(hytranslating equipment for translating 15\ basic supergroups into the basic assembly\ No.\ 1 of 15\ basic supergroups and vice versa; .LP \(em 15\(hysupergroup assembly equipment for translating basic assembly\ No.\ 1 of 15\ supergroups into the frequency band of the 15\(hysupergroup assembly\ No.\ 3 and vice versa; .LP \(em supermastergroup\(hytranslating equipment for translating 15\(hysupergroup assembly\ No.\ 3 into the line\(hyfrequency band and vice versa. .bp .PP \fINote\ 1\fR \ \(em\ Figure\ 1/G.211, \fIa)\fR and \fIc)\fR gives a recapitulation of the basic frequency bands used in procedure\ 2 in which the through\(hyconnection facilities described in Recommendation\ G.242 are provided. .PP \fINote\ 2\fR \ \(em\ The frequency band occupied by 15\(hysupergroup assembly\ No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band occupied by the basic supermastergroup (8516\ to 12 | 88\ kHz). The equipments which are used for translating into the line\(hyfrequency band and vice versa may therefore be the same. .PP For this reason, these equipments carry the same name of \*Qsupermastergroup\(hytranslating equipment\*U. .RT .sp 2P .LP \fB2\fR \fBThrough\(hyconnection filters\fR .sp 1P .RT .PP Through\(hygroup, supergroup, etc., filters and direct through\(hyconnection filters (see Recommendation\ G.242). .PP The equipment listed under the preceding sentence and \(sc\ 1 above can be interconnected for setting up long groups, supergroups, etc., over several carrier systems. An example of such a link is shown in Figure\ 2/G.211 together with the expressions defined below that are recommended for describing the various parts of a circuit on such a group or supergroup, etc. .PP Figure\ 3/G.211 refers to definitions\ 3.2 to\ 3.11 below. .PP Those of the following definitions that concern \*Qlinks\*U or \*Qsections\*U apply, unless otherwise stated, to the combination of both directions of transmission. A distinction between the two directions of transmission may, however, be necessary in the case of unidirectional, multiple\(hydesignation \*Qlinks\*U or \*Qsections\*U set up over multiple\(hydestination telecommunication satellite systems. .RT .LP .rs .sp 28P .ad r \fBFigure 2/G.211, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP \fB3\fR \fBDefinitions\fR .sp 1P .RT .sp 1P .LP 3.1 \fBline link (using symmetric pairs, coaxial pairs, etc.)\fR .sp 9p .RT .LP \fIF:\ liaison en ligne (\*`a paires sym\*'etriques, \*`a paires coaxiales, etc.)\fR .LP \fIS:\ enlace en l\*'inea (de pares sim\*'etricos, de pares coaxiales, etc.)\fR .PP A transmission path, however provided, together with all the associated equipment, such that the bandwidth available, while not having any specific limits, is effectively the same throughout the length of the link. .PP Within the link there are no direct filtration points nor any through\(hyconnection points for groups, supergroups, etc., and the ends of the link are the points at which the band of line frequencies is changed in some way or other. .RT .sp 1P .LP 3.2 \fBgroup link\fR .sp 9p .RT .LP \fIF:\ liaison en groupe primaire\fR .LP \fIS:\ enlace en grupo primario\fR .PP The whole of the means of transmission using a frequency band of specified width (48\ kHz) connecting two terminal equipments, for example channel translating equipments, wideband sending and receiving equipments (modems, etc.). The ends of the link are the points on group distribution frames (or their equivalent) to which the terminal equipments are connected. .PP It can include one or more group sections. .RT .sp 1P .LP 3.3 \fBsupergroup link\fR .sp 9p .RT .LP \fIF:\ liaison en groupe secondaire\fR .LP \fIS:\ enlace en grupo secundario\fR .PP The whole of the means of transmission using a frequency band of specified width (240\ kHz) connecting two terminal equipments, for example group translating equipments, wideband sending and receiving equipments (modems,\ etc.). The ends of the link are the points on supergroup distribution frames (or their equivalent) to which the terminal equipments are connected. .PP It can include one or more supergroup sections. .RT .sp 1P .LP 3.4 \fBmastergroup link\fR .sp 9p .RT .LP \fIF:\ liaison en groupe tertiaire\fR .LP \fIS:\ enlace en grupo terciario\fR .PP The whole of the means of transmission using a frequency band of specified width (1232\ kHz) connecting two terminal equipments, for example supergroup translating equipments, wideband sending and receiving equipments (modems,\ etc.). The ends of the link are the points on mastergroup distribution frames (or their equivalent) to which the terminal equipments are connected. .PP It can include one or more mastergroup sections. .PP \fINote\fR \ \(em\ As translating procedure\ 2 described under \(sc\ 1 above does not enable mastergroups to be set up, the \*Qmastergroup link\*U concept applies only in procedure\ 1. .RT .sp 1P .LP 3.5 \fBsupermastergroup link\fR .sp 9p .RT .LP \fIF:\ liaison en groupe quaternaire\fR .LP \fIS:\ enlace en grupo cuaternario\fR .PP The whole of the means of transmission using a frequency band of specified width (3872\ kHz) connecting two terminal equipments, for example mastergroup translating equipments, wideband sending and receiving equipments (modems,\ etc.). The ends of the link are the points on supermastergroup distribution frames (or their equivalent) to which the terminal equipments are connected. .bp .RT .PP It can include one or more supermastergroup sections. .PP \fINote\fR \ \(em\ As the frequency band occupied by 15\(hysupergroup assembly\ No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band occupied by the basic supermastergroup (8516\ to 12 | 88\ kHz), the basic supermastergroup link can transmit one supermastergroup or an assembly of 15 supergroups. .RT .sp 1P .LP 3.6 \fB15\(hysupergroup assembly link\fR .sp 9p .RT .LP \fIF:\ liaison en assemblage de 15 groupes secondaires\fR .LP \fIS:\ enlace en agregado de 15 grupos secundarios\fR .PP The whole of the means of transmission using a frequency band of specified width (3716\ kHz) connecting two terminal equipments (supergroup modems permitting the setting\(hyup of a 15\(hysupergroup assembly). The ends of the link are the points on 15\(hysupergroup assembly distribution frames (or their equivalent) to which the terminal equipments are connected. .PP It can include one or more 15\(hysupergroup assembly sections. .PP \fINote\fR \ \(em\ The notion of 15\(hysupergroup assembly link relates to translating procedure\ 2 mentioned in \(sc\ 1 above. It is the equivalent of the \*Qsupermastergroup link\*U concept of the translating procedure\ 1 (900\ telephone channels). .RT .sp 1P .LP 3.7 \fBgroup section\fR .sp 9p .RT .LP \fIF:\ section de groupe primaire\fR .LP \fIS:\ secci\*'on de grupo primario\fR .PP The whole of the means of transmission using a frequency band of specified width (48\ kHz) connecting two consecutive group distribution frames (or equivalent points) via at least one line link. .RT .sp 1P .LP 3.8 \fBsupergroup section\fR .sp 9p .RT .LP \fIF:\ section de groupe secondaire\fR .LP \fIS:\ secci\*'on de grupo secundario\fR .PP The whole of the means of transmission using a frequency band of specified width (240\ kHz) connecting two consecutive supergroup distribution frames (or equivalent points) via at least one line link. .RT .sp 1P .LP 3.9 \fBmastergroup section\fR .sp 9p .RT .LP \fIF:\ section de groupe tertiaire\fR .LP \fIS:\ secci\*'on de grupo terciario\fR .PP The whole of the means of transmission using a frequency band of specified width (1232\ kHz) connecting two consecutive mastergroup distribution frames (or equivalent points) via at least one line link. .PP \fINote\fR \ \(em\ As translating procedure\ 2 described in \(sc\ 1 above does not enable mastergroups to be set up, the \*Qmastergroup section\*U concept applies only in procedure\ 1. .RT .sp 1P .LP 3.10 \fBsupermastergroup section\fR .sp 9p .RT .LP \fIF:\ section de groupe quaternaire\fR .LP \fIS:\ secci\*'on de grupo cuaternario\fR .PP The whole of the means of transmission using a frequency band of specified width (3872\ kHz) connecting two supermastergroup distribution frames (or equivalent points) via at least one line link. .PP \fINote\fR \ \(em\ As the frequency band occupied by 15\(hysupergroup assembly\ No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band occupied by the basic supermastergroup (8516\ to 12 | 88\ kHz), the supermastergroup section can transmit one supermastergroup or an assembly of 15\ supergroups. .bp .RT .LP .rs .sp 47P .ad r \fBFigure 3/G.211, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP 3.11 \fB15\(hysupergroup assembly section\fR .sp 9p .RT .LP \fIF:\ section d'assemblage de 15 groupes secondaires\fR .LP \fIS:\ secci\*'on de agregado de 15 grupos secundarios\fR .PP The whole of the means of transmission using a frequency band of specified width (3716\ kHz) connecting two consecutive 15\(hysupergroup assembly distribution frames (or equivalent points) via at least one line link. .PP \fINote\ 1\fR \ \(em\ Same note as for definition\ 3.6 above. .PP \fINote\ 2\fR \ \(em\ In a country which uses procedure\ 1, a 15\(hysupergroup assembly can be through\(hyconnected without difficulty at the supermastergroup distribution frame. In this case, the 15\(hysupergroup assembly is through\(hyconnected to position\ \fI3\fR (8620\(hy12 | 36\ kHz) instead of position\ \fI1\fR (312\(hy4028\ kHz) as required by the definition of the through\(hyconnection point of such an assembly (see Recommendation\ G.242, \(sc\ 6). This through\(hyconnection point does not therefore correspond to this definition and is not at the end of a 15\(hysupergroup assembly section. .RT .sp 1P .LP 3.12 \fBthrough\(hygroup connection point\fR .sp 9p .RT .LP \fIF:\ point de transfert de groupe primaire\fR .LP \fIS:\ punto de transferencia de grupo primario\fR .PP When a group link is made up of several group sections, they are connected in tandem by means of through\(hygroup filters at points called through\(hygroup connection points. .RT .sp 1P .LP 3.13 \fBthrough\(hysupergroup connection point\fR .sp 9p .RT .LP \fIF:\ point de transfert de groupe secondaire\fR .LP \fIS:\ punto de transferencia de grupo secundario\fR .PP When a supergroup link is made up of several supergroup sections, they are connected in tandem by means of through\(hysupergroup filters at points called through\(hysupergroup connection points. .RT .sp 1P .LP 3.14 \fBthrough\(hymastergroup connection point\fR .sp 9p .RT .LP \fIF:\ point de transfert de groupe tertiaire\fR .LP \fIS:\ punto de transferencia de grupo terciario\fR .PP When a mastergroup link is made up of several mastergroup sections, they are connected in tandem by means of through\(hymastergroup filters at points called through\(hymastergroup connection points. .RT .sp 1P .LP 3.15 \fBthrough\(hysupermastergroup connection point\fR .sp 9p .RT .LP \fIF:\ point de transfert de groupe quaternaire\fR .LP \fIS:\ punto de transferencia de grupo cuaternario\fR .PP When a supermastergroup link is made up of several supermastergroup sections they are connected in tandem by means of through\(hysupermastergroup filters at points called through\(hysupermastergroup connection points. .RT .sp 1P .LP 3.16 \fBthrough\(hy15\(hysupergroup assembly connection point\fR .sp 9p .RT .LP \fIF:\ point de transfert d'assemblage de 15 groupes\fR .LP \fIS:\ punto de transferencia de agregado de 15 grupos secundarios\fR .PP When a 15\(hysupergroup assembly link is made up of several 15\(hysupergroup assembly sections, these sections are interconnected in tandem by means of through\(hy15\(hysupergroup assembly filters at points called through\(hy15\(hy supergroup assembly connection points. .bp .PP As an alternative when the 15\(hysupergroup assembly equipment provides sufficient filtering (corresponding to the definition of through\(hyconnection equipments\ \(em\ see Recommendation\ G.242,\ \(sc\ 6) through\(hy15\(hysupergroup assembly filters can be dispensed with. .PP \fINote\fR \ \(em\ When a 15\(hysupergroup assembly is connected by means of through\(hysupermastergroup filters, the point of interconnection is the through\(hysupermastergroup connection point and not a through\(hy15\(hysupergroup assembly connection point. .RT .sp 1P .LP 3.17 \fBregulated line section (symmetric pairs, coaxial pairs or radio\(hyrelay links, etc.)\fR .sp 9p .RT .LP \fIF:\ section de r\*'egulation de ligne (\*`a paires sym\*'etriques ou\fR \fIcoaxiales ou sur faisceau hertzien, etc.)\fR .LP \fIS:\ secci\*'on de regulaci\*'on de l\*'inea (de pares sim\*'etricos o\fR \fIcoaxiales, o por radio\(hyenlaces, etc.)\fR .PP In a carrier transmission system, a line section on which the line\(hyregulating pilot or pilots are transmitted from end to end without passing through an amplitude\(hychanging device peculiar to the pilot or pilots. .RT .sp 1P .LP 3.18 \fBmain repeater station\fR .sp 9p .RT .LP \fIF:\ station principale de r\*'ep\*'eteurs\fR .LP \fIS:\ estaci\*'on principal de repetidores\fR .PP A station, always the terminal of a line link (see definition\ 3.1\ above), where direct line filtering or demodulation or both together may take place. As a consequence, in such a station there are equalizers and it is possible to find points which are of uniform relative level independent of frequency (\*Qflat points\*U). .PP Such a station, where all the supergroups, for example, are demodulated and brought into the basic supergroup position, is called a \*Qmain terminal station\*U and is of necessity at the end of a regulated\(hyline section. A \*Qmain intermediate station\*U is a station within a regulated\(hyline section where a direct through\(hyconnection takes place. .RT .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCITT Recommendation \fI8\(hychannel terminal equipments\fR , Orange Book, Vol.\ III\(hy1, Rec.\ G.234, ITU, Geneva, 1977. .sp 2P .LP \fBRecommendation\ G.212\fR .RT .sp 2P .sp 1P .ce 1000 \fBHYPOTHETICAL\ REFERENCE\ CIRCUITS\ FOR\ ANALOGUE\ SYSTEMS\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.212'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.212 %' .ce 0 .sp 1P .ce 1000 \fBGENERAL\ DEFINITIONS\fR .ce 0 .sp 1P .LP \fB1\fR \fBhypothetical reference circuit\fR .sp 1P .RT .LP \fIF:\ circuit fictif de r\*'ef\*'erence\fR .LP \fIS:\ circuito ficticio de referencia\fR .PP This is a hypothetical circuit of defined length and with a specified number of terminal and intermediate equipments, this number being sufficient but not excessive. It forms a basis for the study of certain characteristics of long\(hydistance circuits (noise, for example). .RT .sp 2P .LP \fB2\fR \fBhypothetical reference circuit for telephony\fR .sp 1P .RT .LP \fIF:\ circuit fictif de r\*'ef\*'erence pour la t\*'el\*'ephonie\fR .LP \fIS:\ circuito ficticio de referencia para la telefon\*'ia\fR .PP This is a complete telephone circuit (between audio\(hyfrequency terminals) established on a hypothetical international telephone carrier system and having a specified length and a specified number of modulations and demodulations of channels, groups, supergroups, these numbers being reasonably great but not having their maximum possible values. The hypothetical reference circuit has to reflect what is generally expected to be the practical application of the system. .PP Various hypothetical reference circuits for telephony have been defined to allow the coordination of the different specifications concerning the constituent parts of the multichannel carrier telephone systems, so that the complete telephone circuits set up on these systems can meet CCITT standards. .bp .PP In order to take account of the variety of operating conditions and in particular the differences there may be in the size of the countries to be served, the CCITT has defined two categories of hypothetical reference circuits for telephony: .RT .LP \(em a set of hypothetical reference circuits with a length of 2500\ km, .LP \(em a hypothetical reference circuit with a length of 5000 km (see Recommendation\ G.215). .PP The former includes the following hypothetical reference circuits for telephony: .LP \(em on open\(hywire lines (see Recommendation G.311), .LP \(em on symmetric pair cable (see Recommendation G.322), .LP \(em on coaxial pair cable (see Recommendations\ G.332 to G.346 of sections\ 3.3 and 3.4). .PP The 5000 km hypothetical reference circuit is used in various types of carrier systems on coaxial cable and on radio relay systems. .PP The CCIR also has defined the following hypothetical reference circuits for telephony: .RT .LP 1) In line\(hyof\(hysight radio\(hyrelay systems using frequency\(hydivision multiplex, with a capacity of 12 to 60\ telephone channels or of more than 60\ telephone channels (see Recommendation\ G.431 or CCIR Recommendations\ 391\ [2] and\ 392\ [3]); .LP 2) On tropospheric\(hyscatter radio\(hyrelay systems (see CCIR Recommendation\ 396\ [4]); .LP 3) For satellite systems (see CCIR Recommendation\ 352\ [5]). .PP Each of these various hypothetical reference circuits has the same total length .FS With the exception of the hypothetical reference circuits for satellite systems and for circuits of 5000\ km. .FE and they are all used in the same way. They are only a guide for planning carrier systems. .PP These hypothetical reference circuits allow designers to study through connection between different carrier systems at basic groups, supergroups,\ etc., as discussed in Recommendation\ G.211. Moreover, when they contain more than one pair of channel modulators and demodulators, they also allow the designers to study an international switched connection having the same total length. .RT .sp 2P .LP \fB3\fR \fBhomogeneous section\fR .sp 1P .RT .LP \fIF:\ section homog\*`ene\fR .LP \fIS:\ secci\*'on homog\*'enea\fR .PP A section without diversion or modulation of any channel groups, supergroups, etc., established on the system which is being considered except for those modulations or demodulations defined at the ends of the section. .PP All the hypothetical reference circuits defined above consist of homogeneous sections of equal length [6, 9\ or 12\ sections .FS The number is not specified for the tropospheric\(hyscatter radio\(hyrelay systems. .FE as the case may be]. .PP It is assumed that at the end of each homogeneous section, the channels, groups, supergroups,\ etc., are connected through at random. .RT .LP .sp 2P .LP \fB4\fR \fBpsophometric power\fR .sp 1P .RT .LP \fIF:\ puissance psophom\*'etrique\fR .LP \fIS:\ potencia sofom\*'etrica\fR .PP Where square law addition (power addition) of noise can be assumed, it has been found convenient for calculations and design of international circuits to use the idea of psophometric power as defined below: \v'6p' .RT .sp 1P .ce 1000 psophometric power = @ { psophometric~voltage) \u2\d } over { 00 } @ .ce 0 .sp 1P .LP or .LP psophometric power = @ { psophometric~e.m.f.) \u2\d } over { ~\(mu~600 } @ .bp .sp 1P .ce 1000 .ce 0 .sp 1P .PP A convenient unit is the micro\(hymicrowatt or picowatt (pW), and this equation can then be given as follows: \v'6p' .sp 1P .ce 1000 psophometric power = @ { psophometric~e.m.f.~in~mV) \u2\d } over { .0024 } @ (pW). .ce 0 .sp 1P .LP .sp 1 .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fI4\(hyMHz valve\(hytype systems on standardized\fR \fI2.6/9.5\(hymm coaxial cable pairs\fR , Orange Book, Vol.\ III\(hy1, Rec.\ G.338, ITU, Geneva,\ 1977. .LP [2] CCIR Recommendation \fIHypothetical reference circuit for radio\(hyrelay\fR \fIsystems for telephony using frequency\(hydivision multiplex with a\fR \fIcapacity of 12 to 60\ telephone channels\fR , Vol.\ IX, Rec.\ 391, Dubrovnik,\ 1986. .LP [3] CCIR Recommendation \fIHypothetical reference circuit for radio\(hyrelay\fR \fIsystems for telephony using frequency\(hydivision multiplex with a\fR \fIcapacity of more than 60\ telephone channels\fR , Vol.\ IX, Rec.\ 392, Dubrovnik,\ 1986. .LP [4] CCIR Recommendation \fIHypothetical reference circuit for trans\(hyhorizon\fR \fIradio\(hyrelay systems for telephony using frequency\(hydivision\fR \fImultiplex,\fR Vol.\ IX, Rec.\ 396, Dubrovnik,\ 1986. .LP [5] CCIR Recommendation \fIHypothetical reference circuits for telephony and\fR \fItelevision in the fixed satellite service\fR , Vol.\ IV, Rec.\ 352, Dubrovnik,\ 1986. .sp 2P .LP \fBRecommendation\ G.213\fR .RT .sp 2P .sp 1P .ce 1000 \fBINTERCONNECTION\ OF\ SYSTEMS\ IN\ A\ MAIN\ REPEATER\ STATION\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.213'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.213 %' .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1964; further amended)\fR .sp 9p .RT .ce 0 .sp 1P .PP The CCITT finds it necessary to define separation points between various types of equipment, both in cable systems and in radio\(hyrelay systems. These separation points are defined below and the CCIR has adopted the same definitions when preparing its Recommendation\ 380\ [1] (see also Recommendation\ G.423). .sp 1P .RT .sp 2P .LP See definitions of Recommendation\ G.211. .FE \fB1\fR \fBDefinition of\fR \fR \fBtelephony input and output points for the\fR \fBline link\fR .sp 1P .RT .PP These are points (marked\ \fIT\fR and\ \fIT\fR ` in Figure\ 1/G.213) located in principle in a main repeater station where the standard conditions given below are found at the output and input of a line link (comprising a cable system or radio link). These standard conditions permit interconnection with other line links or with telephony equipment (including, where appropriate, direct through\(hyconnection filters as well as translating equipment). .PP At such a point,\ \fIT\fR , on the receiving side, the following conditions apply: .RT .LP 1) All the telephony groups (groups, supergroups, mastergroups, etc.) are still assembled in the positions in the frequency spectrum which they occupy on the line. .LP 2) All the line\(hyregulating, monitoring or frequency\(hycomparison pilots on the H.F. line are, or can be, suppressed (the recommended suppression attenuations are given in Recommendations\ G.242 and\ G.243), according to whether the station is at the end of a regulated\(hyline section or not .FS The interconnecting point between a radio\(hyrelay system and a long cable system is always the terminal of a regulated\(hyline section (CCIR Recommendation 381\ [2] and hence all these pilots are suppressed at that point. For the distinction between a \*Qshort\*U and a \*Qlong\*U cable system, see Recommendation G.423, \(sc\ 1.2). .FE . .bp .LP 3) The relative level of all the telephony channels is independent of frequency, i.e. any de\(hyemphasis network is included in the line equipment. .LP 4) No special suppression of additional measuring frequencies is foreseen (CCITT Recommendation\ G.423 for cable systems, CCIR Recommendation\ 381\ [2] for radio\(hyrelay systems). .PP A similar point\ \fIT\fR ` | is defined for the sending side, where the following conditions are met: .LP a) All the telephony groups (groups, supergroups, mastergroups, etc.) are still assembled in the positions in the frequency spectrum which they occupy on the line, except where use is made of direct through\(hyconnection filters provided as part of the line equipment. .LP b) [Follows from the situation at\ \fIT\fR according to condition\ 2) above.] .LP c) The relative level of all the telephony channels is independent of frequency, i.e. any pre\(hyemphasis network is included in the line equipment. .LP d) The additional measuring frequencies are transmitted. .LP .rs .sp 28P .ad r \fBFIGURE 1/G.213, p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP \fIGeneral remarks\fR .sp 9p .RT .PP \fINote\ 1\fR \ \(em\ Figure\ 1/G.213 gives an example only. .PP \fINote\ 2\fR \ \(em\ If the station is within a regulated line section, provision must be made for the line\(hyregulating pilots to be passed through, either by means of the telephony direct through\(hyconnection filter itself or by means of a special pilot through\(hyconnection filter. To cater for this case, and for the case where the station forms a boundary between two regulated line sections, a pilot input to, and output from, the line link, separate from the telephony input and output points\ \fIT\fR and\ \fIT\fR `, should be provided; these are points\ \fIP\fR and\ \fIP\fR ` in Figure\ 1/G.213. .bp .PP \fINote\ 3\fR \ \(em\ (Applicable to all systems, irrespective of the number of channels): .PP When there is direct through\(hyconnection of part of the groups, supergroups,\ etc. with the aid of the direct through\(hyconnection filters fitted into the line equipment for this purpose, it is up to each Administration to fix the relative levels at the filter access points (which are different from the access point\ \fIT\fR and\ \fIT\fR ` mentioned above). .PP \fINote\ 4\fR \ \(em\ The levels at points\ \fIT\fR and\ \fIT\fR ` have been chosen so as to permit the insertion of the various direct through\(hyconnecting and translating equipments which may be necessary in the main station. The difference in level between points\ \fIR\fR and\ \fIT\fR and between points\ \fIT\fR ` and\ \fIR\fR ` allows for the cabling interconnecting these points, which may be at some distance from each other and, in favourable circumstances, for a blocking filter having only a small loss in the passband. .RT .sp 2P .LP \fB2\fR \fBDefinition of the\fR \fBpoints of international connection at\fR \fBbaseband frequencies of a radio\(hyrelay system\fR .sp 1P .RT .PP The points of international interconnection at baseband frequencies, called\ \fIR\fR ` and\ \fIR\fR , form the input and output of a radio\(hyrelay system, conforming to CCITT Recommendation\ G.423 and CCIR Recommenda tion\ 380\ [1]. .PP At the output of the radio\(hyrelay system (point\ \fIR\fR ), the following conditions are found in the baseband: .RT .LP 1) All the telephony groups (groups, supergroups, mastergroups,\ etc.), and the pilots (line regulating, frequency comparison and monitoring pilots) included in the baseband are assembled in the position in which they are transmitted, as defined in the CCITT and CCIR Recommendations mentioned above. .LP 2) All the continuity and switching pilots and other signals transmitted in a radio\(hyrelay system outside the telephony band, inherent to the radio equipment, are suppressed in accordance with CCIR Recommendation\ 381\ [2]. .LP 3) Any radio\(hyrelay protection switching shall be performed as part of the radio\(hyrelay system. With diversity reception, the combined output of the receivers used corresponds to point\ \fIR\fR . .LP 4) Any de\(hyemphasis networks are part of the radio equipment, so that the relative levels of the telephone channels are independent of frequency, within the limits of the tolerances stated in Note\ 7 of CCIR Recommendation\ 380\ [1] (\(+- | \ dB relative to the nominal value). .PP A similar point\ \fIR\fR ` is defined for the baseband input of a radio\(hyrelay system, where similar conditions are to be met. .sp 2P .LP \fB3\fR \fBRelative levels recommended by the CCITT at the telephony\fR \fBoutput and input\fR (Points\ \fIT\fR and\ \fIT\fR ` in Figure\ 1/G.213) .sp 1P .RT .PP At the interconnection points\ \fIT\fR and\ \fIT\fR ` for telephony defined in \(sc\ 1\ above, Table\ 1/G.213 shows the relative levels which are recommended for cable systems, each of which is defined by the maximum number of telephone channels that it can provide. (Similar levels are recommended by the CCITT and the CCIR for radio systems of corresponding capacity\ \(em\ see Recommendation\ G.423 and\ CCIR Recommendation\ 380\ [1].) .PP The cable systems to which this Recommendation applies are modern systems with transistor equipment and to new versions of other systems previously standardized by the CCITT. .PP The recommended levels at\ \fIT\fR and\ \fIT\fR ` make it possible to insert all the translating or direct through\(hyconnecting equipment which may be necessary; this does not define the relative levels in translating and direct through\(hyconnecting equipment, which depend on other considerations. .RT .LP .rs .sp 8P .LP .bp .ce \fBH.T. [T1.213]\fR .ce TABLE\ 1/G.213 .ce \fBRecommended relative levels for interconnection .ce of various cable systems\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(54p) | cw(54p) | cw(36p) sw(30p) | cw(54p) , ^ | ^ | c | c | ^ . { Maximum number of telephone channels } Impedance (ohms) { Relative power level per channel at a main station } Remarks { Receiving (Point \fIT\fR ) (dBr) } { Sending (Point \fIT\fR `) (dBr) } _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) . 24, 36, 48 150 (bal.) \(em23 \(em36 _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) . \ 60 120 150 (bal.) or 75 (unbal.) \(em23 \(em36 _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) . 300 75 (unbal.) \(em23 \(em36 _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) . 600, 960, 1200 1260 75 (unbal.) \(em23 or \(em33 \(em36 or \(em33 See note _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) . 2700 75 (unbal.) \(em33 \(em33 { See also Recommendations G.333 and J.77 [3] } _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) . 3600 75 (unbal.) \(em33 \(em33 { See also Recommendations G.334 and J.77 [4] } _ .T& cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) . 10 | 00 75 (unbal.) \(em33 \(em33 .TE .LP \fINote\fR \ \(em\ For 600, 960, 1200 and 1260 channel systems Administrations have the choice between the alternative pairs of level shown for points \fIT\fR and \fIT\fR ` which apply in the following circumstances: .LP 1) \(em23 dBr at point \fIT\fR , \(em36 dBr at point \fIT\fR `, where conformity with well\(hyestablished equipment using similar levels is necessary; .LP 2) \(em33 dBr at each of the points \fIT\fR and \fIT\fR `, in other cases, for example, to new stations wholly equipped with transistor equipments. .nr PS 9 .RT .ad r \fBTable 1/G.213 [T1.213], p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCIR Recommendation \fIInterconnection at baseband frequencies of\fR \fIradio\(hyrelay systems for telephony using frequency\(hydivision multiplex\fR , Vol.\ IX, Rec.\ 380, Dubrovnik,\ 1986. .LP [2] CCIR Recommendation \fIConditions relating to line regulating and other\fR \fIpilots and to limits for the residues of signals outside the baseband\fR \fIin the interconnection of radio\(hyrelay and line systems for telephony\fR , Vol.\ IX, Rec.\ 381, Dubrovnik,\ 1986. .LP [3] CCITT Recommendation \fIUse of a 12\(hyMHz system for the simultaneous\fR \fItransmission of telephony and television\fR , Vol.\ III, Rec.\ J.73. .LP [4] CCITT Recommendation \fICharacteristics of the television signals\fR \fItransmitted over 18\(hyMHz and 60\(hyMHz systems\fR , Vol.\ III, Rec.\ J.77. .LP .rs .sp 3P .LP .bp .sp 2P .LP \fBRecommendation\ G.214\fR .RT .sp 2P .sp 1P .ce 1000 \fBLINE\ STABILITY\ OF\ CABLE\ SYSTEMS\fR .FS Stability of transmission is also the subject of Recommendation\ M.160 of Volume\ IV\ [1]. .FE .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.214'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.214 %' .ce 0 .sp 1P .ce 1000 \fI(Mar del Plata, 1968)\fR \v'1P' .sp 9p .RT .ce 0 .sp 1P .PP Line regulation has a threefold purpose: .sp 1P .RT .LP 1) to keep actual line relative levels within such limits that thermal or intermodulation noise never exceeds acceptable values; .LP 2) to keep levels at the ends of regulated\(hyline sections within such limits that regulators of the following multiplex equipment are able to function; .LP 3) to ensure that regulation is precise enough to make it generally unnecessary to provide an automatic group regulator and/or supergroup regulator for the group, supergroup,\ etc., links set up on a single regulated\(hyline section. .PP It appears that all three objectives will be secured if levels at the end of the longest regulated section envisaged are stabilized to \(+- | \ dB at any frequency in the band transmitted. .sp 2P .LP The CCITT therefore \fIunanimously recommends that:\fR .sp 1P .RT .PP Designers of line\(hyregulating systems take account of the daily and seasonal variations in temperature to which the cables and repeaters are likely to be subjected, the predictable ageing of components, and also the nominal range of variation of power supplies, assuming that appropriate precautions are taken in the placing of the cable, in the design of buildings and in regulation of power supplies. .PP As a design objective for the residual effects of sustained power and temperature variations, and the predictable ageing of components, over the ranges expected in any period between two successive manual adjustments, the change in insertion gain of a regulated\(hyline section at any frequency in the transmitted band should not exceed 1\ dB. .PP For the purposes of this Recommendation, it is assumed that a regulated\(hyline section will not be longer than a homogeneous section of the hypothetical reference circuit applicable to the type of system considered and that the interval between two successive manual adjustments will be not less than a fortnight. .PP The variations in gain of a regulated\(hyline section in service is also affected by maintenance operations and adjustments. The design objective excludes these effects. .PP Moreover, the dynamic stability of the regulating system should be such that any swinging of the gain is damped and at a suitable rate as a result of an abrupt change in pilot level. If, for example, the pilot level is suddenly increased by 2\ dB at the origin of the regulated\(hyline section, the pilot level must not increase or diminish by more than 2\ dB at the end of the regulated\(hyline section. The resulting fluctuations in pilot level must fall off progressively. .PP \fINote\fR \ \(em\ It may be desirable to specify immunity of the regulating system to interference from components of television signals when transmitted. .RT .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCITT Recommendation \fIStability of transmission\fR , Vol.\ IV, Rec.\ M.160. .LP .sp 4 .bp .sp 2P .LP \fBRecommendation\ G.215\fR .RT .sp 2P .ce 1000 \fBHYPOTHETICAL\ REFERENCE\ CIRCUIT\ OF\ 5000\ km\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.215'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.215 %' .ce 0 .sp 1P .ce 1000 \fBFOR\ ANALOGUE\ SYSTEMS\fR .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1980)\fR .sp 9p .RT .ce 0 .sp 1P .LP \fB1\fR \fBComposition of the hypothetical reference circuit\fR .sp 1P .RT .PP This hypothetical reference circuit is 5000 km long and applies to various types of carrier systems on coaxial cable and radio\(hyrelay systems, specially designed for very long international circuits. It has, for each direction of transmission, a total of: .RT .LP \(em one pair of channel modulators which includes translation from the audio\(hyfrequency band to the basic group and vice versa; .LP \(em three pairs of group modulators, each pair including translation from the basic group to the basic supergroup and vice versa; .LP \(em six pairs of supergroup modulators, each pair including translation from the basic supergroup to a higher order modem and vice versa; .LP \(em twelve pairs of higher order modulators, each pair providing the necessary modulation stages to and from the line frequency. .PP Figure 1/G.215 shows the principle of the hypothetical reference circuit. .PP This hypothetical reference circuit consists of 12 homogeneous sections of equal length (see Recommendation\ G.212). Two homogeneous sections may be connected in tandem without translating equipment at the junction if the transmission system has suitable line regulating capability and does not introduce undesirable noise and crosstalk into any telephone channel. .RT .LP .rs .sp 10P .ad r \fBfigure 1/G.215, p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP \fB2\fR \fBDesign objectives for\fR \fBcircuit noise\fR .FS Although the noise objective for the 5000\ km HRC is in principle agreed, some countries will not be soon in the position to install equipment of the desired performance, and will continue to use existing systems on the very long national and international circuits, according to established planning and design practices. .FE .sp 1P .RT .PP The same noise values as for the 2500 km HRC apply (Recommendation\ G.222, \(sc\ 1). .PP \fINote\ 1\fR \ \(em\ This design objective is in line with Recommendation\ G.123, \*QCircuit noise in national networks\*U, which in \(sc\ 2.1.1 recommends that the line noise in channels used to provide very long\(hydistance circuits (over 2500\ km) should not exceed 2\ pW0p/km. .PP \fINote\ 2\fR \ \(em\ Designers are expected to fit their noise distribution curves fall below all \(sc\(sc\ 1.1 and\ 1.2 of Recommendation\ G.222. .PP \fINote\ 3\fR \ \(em\ In applying these design objectives, \(sc\(sc\ 2.4 through\ 2.7 of Recommendation\ G.222 should be taken into account. .bp .PP The subdivision of the total noise between the various sources of noise is left entirely to the designer of the system, within the limits of 2500\ pW0p for the terminal equipment and 7500\ pW0p for the line. This allocation is intended to permit the use of modulating equipment meeting the maximum values recommended in Table\ 1/G.222 of Recommendation\ G.222 as indicated in Table\ 1/G.215. .RT .ce \fBH.T. [T1.215]\fR .ce TABLE\ 1/G.215 .T& lw(72p) | lw(72p) | lw(42p) | lw(42p) . .T& lw(72p) | lw(72p) | lw(42p) | lw(42p) . Total: 2500 pW0p .TE .LP \fINote\fR \ \(em\ This Table assumes two stages of modulation in the higher modulator. .nr PS 9 .RT .ad r \fBTable 1/G.215 [T1.215], p.\fR .sp 1P .RT .ad b .RT .IP \fB2.2\ General recommendations\fR .sp 1P .RT .sp 2P .LP \fBRecommendation\ G.221\fR .RT .sp 2P .sp 1P .ce 1000 \fBOVERALL\ \fR \fBRECOMMENDATIONS\ RELATING\ TO\ CARRIER\(hyTRANSMISSION | fR \fBSYSTEMS\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.221'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.221 %' .ce 0 .sp 1P .ce 1000 \fI(amended at Geneva, 1972 and 1980)\fR .sp 9p .RT .ce 0 .sp 1P .LP \fB1\fR \fBCharacteristics of complete circuits\fR .sp 1P .RT .PP The characteristics of complete circuits, measured between audio\(hyfrequency terminals (overall loss in terminal service and in transit service, frequency bands effectively transmitted and attenuation distortion, variation of overall loss with time, phase distortion, stability, crosstalk,\ etc.) should meet the general conditons for 4\(hywire telephone circuits indicated in Section\ 1 of the Series\ G Recommendations. .RT .sp 2P .LP \fB2\fR \fBLinear crosstalk\fR .sp 1P .RT .sp 1P .LP 2.1 \fIOverall requirements\fR .sp 9p .RT .PP The requirements as regards crosstalk ratio between circuits in the case of telephony are the subjects of Recommendation\ G.134\ [1] and the Recommendation cited in\ [2]; for go\(hyto\(hyreturn crosstalk the Recommendation cited in\ [3] applies. .bp .PP As carrier transmission systems are also used for setting up sound\(hyprogramme circuits, the relevant requirements given in the Series\ J Recommendations should be taken into consideration. Recommendation\ J.18\ [4] gives general guidance on how the higher crosstalk ratios appropriate to sound\(hyprogramme transmissions are achieved in a telephone network. .PP In any case the near\(hyend crosstalk ratio between the two directions of transmission at all frequencies used for the regulating and measuring pilots on carrier systems should be not less than\ 40\ dB. .RT .sp 1P .LP 2.2 \fIIntelligible crosstalk caused by intermodulation with a signal\fR \fIwhich is a multiple of 4\ kHz\fR .sp 9p .RT .PP Intelligible crosstalk may arise between circuits by way of intermodulation with a signal which is a multiple of 4\ kHz, e.g.\ a line\(hyregulating pilot. A design objective is that the intelligible crosstalk ratio in a single homogeneous section of the appropriate hypothetical reference circuit should be not less than 74\ dB. .RT .sp 2P .LP \fB3\fR \fBNoise transmitted between interconnected systems\fR .sp 1P .RT .PP A failure or malfunction in a chain of repeaters may lead to large values of noise in one or several signal bands being transmitted by that chain. It is known that such high noise levels are generally caused by the operation of particular types of automatic line regulators. Given that such high noise levels may be transmitted to other chain links, and may overload those to which they are interconnected, it is desirable and recommended that care should be taken in the future in order to avoid such troubles. .PP Possible methods of dealing with this problem are described in Supplement\ No.\ 4\ [5]. .PP In respect of radio\(hyrelay links, it will be the concern of CCIR to enumerate suitable precautions. .RT .sp 2P .LP \fB4\fR \fBSingle tone interference\fR .sp 1P .RT .PP The Recommendation cited in\ [6] indicates a limit for the single tone interference level in telephone circuits. Depending on the origin of such interferences, wide\(hyband services and non\(hytelephony services (e.g.\ sound\(hyprogramme circuits, etc.) may also be affected. This should be considered when defining limits for transmission systems. .PP Practical experience shows that broadcasting transmitters are the main external source of single tone interference. In order to be usable under normal environmental working conditions, the carrier transmission equipment should be designed in such a way that it allows a certain electromagnetic field strength in its vicinity, caused by transmitters. A figure of 0.5 to\ 0.7\ V/m within a station should be tolerated by equipment which is installed as normally specified and working under normal conditions. Where higher field strengths are .PP known to be expected, suitable screening measures in the building may have to be adopted. Special attention should also be given to the stating cabling including power distribution and to the wiring of distribution racks to prevent interferences from entering the equipment via these points. .PP \fINote\fR \ \(em\ The Supplement No. 27 contains some information on possible measures to reduce effects from interference and on measuring methods concerning interference. .RT .sp 2P .LP \fB5\fR \fBTotal interference power\fR .sp 1P .RT .PP In addition to the above limitation of the single tone interference, it should be ascertained that the total interference power in each telephone channel within the band 300\(hy3400\ Hz, for each individual case of interference, should be lower than\ \(em65\ dBm0. .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fILinear crosstalk\fR , Vol.\ III, Rec.\ G.134. .LP [2] CCITT Recommendation \fIGeneral performance objectives applicable to all\fR \fImodern international circuits and national extension circuits\fR , Vol.\ III, Rec.\ G.151, \(sc\ 4.1. .LP [3] \fIIbid.\fR , \(sc\ 4.2. .LP [4] CCITT Recommendation \fICrosstalk in sound\(hyprogramme circuits set up on\fR \fIcarrier systems\fR , Vol.\ III, Rec.\ J.18. .LP [5] \fICertain methods of avoiding the transmission of excessive noise\fR \fIbetween interconnected systems\fR , Green Book, Vol.\ III\(hy2, Supplement No.\ 4, ITU, Geneva, 1973. .LP [6] CCITT Recommendation \fIGeneral performance objectives applicable to all\fR \fImodern international circuits and national extension circuits\fR , Vol.\ III, Rec.\ G.151, \(sc\ 8. .bp .sp 2P .LP \fBRecommendation\ G.222\fR .RT .sp 2P .ce 1000 \fBNOISE\ OBJECTIVES\ FOR\ DESIGN\ OF\ CARRIER\(hyTRANSMISSION\ SYSTEMS\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.222'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.222 %' .ce 0 .sp 1P .ce 1000 \fBOF\ 2500\ km\fR .ce 0 .sp 1P .LP \fB1\fR \fBDesign objectives in respect of noise produced by the line and\fR \fBthe frequency division modulating equipment on hypothetical reference\fR \fBcircuits of 2500\ km for telephony\fR .sp 1P .RT .PP In order to ensure that multichannel carrier systems on cable and on radio\(hyrelay links shall comply with standards of performance considered as equivalent in respect of noise, the following design objectives should apply to the noise \fIat a zero relative level point\fR in any telephone channel having the same composition as the hypothetical reference circuit on such systems. .RT .LP .PP 1.1 To ensure adequate performance in respect of telephone speech and signalling on cable systems, the mean psophometric noise power over one minute shall not exceed 10 | 00 pW0p. .sp 9p .RT .PP 1.2 To ensure adequate performance in respect of telephone speech and signalling on radio\(hyrelay links: .sp 9p .RT .PP 1.2.1 the mean psophometric noise power over one minute shall not exceed 10 | 00\ pW0p for more than 20% of any month; .PP 1.2.2 the mean psophometric noise power over one minute shall not exceed 50 | 00\ pW0p for more than 0.1% of any month; .PP 1.2.3 the unweighted noise power, measured or calculated with an integrating time of\ 5\ ms shall not exceed 1 | 00 | 00\ pW0 (10\u6\d\ pW0) for more than\ 0.01% (10\uD\dlF261\u4\d) of any month. .PP \fINote\fR \ \(em\ For carrier transmission systems with one\(hyminute mean noise power distributions which are not well defined, the inclusion of another one\(hyminute mean noise clause would be desirable to ensure equivalent performance for all systems. This clause would specify that: .PP The mean psophometric noise power over one minute shall not exceed 20 | 00\ pW0p for more than\ 3% of any month. .PP This clause has not been specifically included because the CCIR has determined that for radio\(hyrelay links, the application of clauses 1.2.1 and\ 1.2.2 are sufficient to ensure, with high probability, that the additional clause will also be satisfied. .RT .PP 1.3 If it is intended to use amplitude\(hymodulated voice\(hyfrequency telegraph equipment for 50\ bauds conforming to the Series\ R Recommendations and to obtain the quality shown in Recommendation\ F.10\ [1], the mean nonweighted noise power over\ 5\ ms must not exceed 10\u6\d\ pW0 during more than\ 0.001% (10\uD\dlF261\u5\d) of any month, nor more than\ 0.1% of any hour, for cable systems and for radio\(hyrelay links. .sp 9p .RT .PP If frequency\(hymodulated voice\(hyfrequency telegraph equipment operating at 50\ bauds is used, it is to be expected that the quality specified in \(sc\(sc\ 1.1 and\ 1.2 respectively above will be satisfactory as far as the telegraph transmission is concerned. .PP The conditions under which the above design objectives should apply are given in \(sc\ 2\ below. .RT .sp 2P .LP \fB2\fR \fBConditions in which the design objectives for hypothetical\fR \fBreference circuits apply\fR .sp 1P .RT .PP 2.1 The values mentioned in \(sc\ 1\ above are design objectives and it is not intended that they should be quoted in specifications for equipment or used for acceptance tests. The noise on a homogeneous section of an actual carrier system is dealt with in Recommendation\ G.226. .sp 9p .RT .PP The following Recommendations specify the conditions in which these general objectives apply to different types of system, account being taken of the special characteristics of each system: .LP \(em symmetric pair cable systems (Recommendation\ G.322); .LP \(em symmetric pair cable \*Q12\ +\ 12\*U systems (Recommendation\ G.326); .LP \(em 4\(hyMHz systems (Recommendation\ G.338\ [2]), 12\(hyMHz systems (Recommendations\ G.332 and\ G.339), 18\ MHz systems (Recommendation\ G.334) and 60\ MHz systems (Recommendation\ G.333) on 2.6/9.5\(hymm coaxial pairs; .bp .LP \(em systems on 1.2/4.4\(hymm coaxial pairs (Recommendations\ G.341, G.343, G.344, G.345 and\ G.346); .LP \(em radio\(hyrelay links using frequency\(hydivision multiplex (Recommendation\ 393\ [3] of the CCIR). .PP In particular, Recommendation\ G.442 lays down objectives for the use of amplitude\(hymodulation voice\(hyfrequency telegraphy used in line\(hyof\(hysight radio\(hyrelay systems. .PP Tropospheric\(hyscatter radio\(hyrelay systems should meet the objectives of this Recommendation, or other objectives, according to the circumstances of operation (see CCIR Recommendation\ 397\ [4]). .PP Other objectives are recommended for systems providing 12\ carrier circuits on an open\(hywire pair (see Recommendation\ G.311). .RT .PP 2.2 Designers are expected to fit their distribution curves to fall below both points given in \(sc\ 1.2.1 and \(sc\ 1.2.2\ above. .PP 2.3 In connection with \(sc 1.2.2 above, the CCITT would have preferred to indicate a figure of 100 | 00\ pW0p (average psophometric power over one minute at a zero relative level point), not to be exceeded during more than\ 0.01% of any month. On account of difficulties in measurement, a figure of 50 | 00\ pW0p for 0.1% of any month has been shown. .PP 2.4 Within each homogeneous section of a hypothetical reference circuit, the telephone channels will occupy the same position in relation to each other. Within these sections, certain intermodulation products (those of odd order) tend to add on the basis of linear addition of voltages, but between sections it may be considered that in respect of noise a power\(hyadditive law applies exclusively. .PP In a part of a hypothetical reference circuit consisting of one or more equal homogeneous sections, the one\(hyminute mean noise power not exceeded during 20% of any month shall be considered to be proportional to the number of homogeneous sections involved. .PP 2.5 In parts of a hypothetical reference circuit consisting of one or more equal homogeneous sections, the small percentage of any month in which the one\(hyminute mean power may exceed the design objective for 0.1% of the time or less shall be regarded as proportional to the number of homogeneous sections involved. This principle also applies to the objective mentioned in \(sc\ 1.2.3\ above. .PP 2.6 Although in principle it is to be understood that the general noise objectives are all\(hyembracing, in practice it is recognized that there will be abnormalities from time to time which will result in additional noise sources becoming evident. Often, such extra contributions can be accommodated within the margin available within the system design. In other cases, no concern need be felt provided that such additional contributions are small compared to the general objective, for example, less than 10% of the power or probability of occurrence respectively. .PP In any case, all necessary precautions should be taken during the installation and putting into service of the systems so that noises of external origin are reduced to a negligible value of, at the most, 10% of the limits fixed as objectives. .PP 2.7 Recommendation\ G.223 gives the other hypotheses which are recommended for the calculation of the noise on the hypothetical reference circuits for telephony. .sp 2P .LP \fB3\fR \fBCircuits more than 2500 kilometres long\fR .sp 1P .RT .PP 3.1 The CCITT recognizes that in order to meet national and international noise performance objectives some large countries have found it necessary to introduce terrestrial FDM carrier transmission systems that are based on the hypothetical reference circuit described in Recommendation\ G.215. The noise performance objective for these systems corresponds approximately to 5000\ pW0p on the 2500\ km hypothetical reference circuit instead of the 10 | 00\ pW0p mentioned in \(sc\(sc\ 1.2.1 and 1.2.2 above. These values include the noise contributed by multiplex equipment. .sp 9p .RT .PP 3.2 The basic hypothetical reference circuit for satellite systems is defined in CCIR Recommendation\ 352, and provisional noise objectives appropriate to the design of such systems in consideration of the values contained in \(sc\ 1 above, are contained in CCIR Recommendation\ 353\ [6]. .sp 2P .LP \fB4\fR \fBDesign objectives for noise produced by modulating equipments and additional equipments\fR .sp 1P .RT .PP The general objectives mentioned in \(sc\ 1\ above include the noise produced by modulating and additional equipments. The mean psophometric power, which corresponds to the noise produced by all modulating equipment mentioned in the .bp .PP definition of the hypothetical reference circuit in question and by all additional equipment, should not exceed 2500\ picowatts at a zero relative level point. This value of psophometric power refers to the whole of the noise due to various sources (thermal noise, intermodulation, crosstalk, power supplies,\ etc.). Its allocation among the various equipments can to a certain extent be left to the discretion of design engineers. However, to ensure a measure of agreement in the allocation chosen by different Administrations, the maximum values given in Table\ 1/G.222 are recommended for the modulating equipments. .PP The allocation of a large part of the noise to channel\(hymodulating equipment is justified because these equipments are the most numerous in a network and therefore are constructed as economically as possible. .PP For the through\(hyfilters a noise objective of a maximum of 10\ pW0p is recommended. This value refers to the nominal band of the through\(hyconnected groups; the noise outside that band must be considerably lower, to avoid a significant contribution of noise to channels situated in adjacent frequency bands. .PP For other units of additional equipment (regulating equipment, equalizers, standby switching equipment, etc.) a value of about 15\ pW0p is indicated as a guideline to the designer. .PP The above statement does not apply to line standby switching equipment whose noise has to be considered together with that of the line. .PP The load assumption of through\(hyfilters and additional equipments should be in line with Recommendation\ G.223, G.228 and G.230. Account should be taken of the possible presence of additional signals outside the nominal frequency band arising from adjacent channels. .RT .LP .rs .sp 29P .ad r \fBTable 1/G.222 (maintenu) T1.222, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fICharacter error rate objective for telegraph\fR \fIcommunication using 5\(hyunit start\(hystop equipment\fR , Vol.\ II, Rec.\ F.10. .LP [2] CCITT Recommendation \fI4\(hyMHz valve\(hytype systems on standardized\fR \fI2.6/9.5\(hymm coaxial cable pairs\fR , Orange Book, Vol.\ III\(hy1, Rec.\ G.338, ITU, Geneva,\ 1977. .LP [3] CCIR Recommendation \fIAllowable noise power in the hypothetical reference circuit for radio\(hyrelay systems for telephony using frequency\fR \fIdivision multiplex\fR , Vol.\ IX, Rec.\ 393, Dubrovnik,\ 1986. .LP [4] CCIR Recommendation \fIAllowable noise power in the hypothetical\fR \fIreference circuit for trans\(hyhorizon radio\(hyrelay systems for telephony\fR \fIusing frequency division multiplex\fR , Vol.\ IX, Rec.\ 397, Dubrovnik,\ 1986. .LP [5] CCIR Recommendation \fIHypothetical reference circuits for telephony and\fR \fItelevision in the fixed satellite service\fR , Vol.\ IV, Rec.\ 352, Dubrovnik,\ 1986. .LP [6] CCIR Recommendation \fIAllowable noise power in the hypothetical\fR \fIreference circuit for frequency\(hydivision multiplex telephony in the\fR \fIfixed satellite service\fR , Vol.\ IV, Rec.\ 353, Dubrovnik,\ 1986. \v'1P' .sp 2P .LP \fBRecommendation\ G.223\fR .RT .sp 2P .ce 1000 \fBASSUMPTIONS\ FOR\ THE\ \fR \fBCALCULATION\ OF\ NOISE\ ON\ HYPOTHETICAL\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.223'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.223 %' .ce 0 .sp 1P .ce 1000 \fBREFERENCE\ CIRCUITS\ FOR\ TELEPHONY\fR .ce 0 .sp 1P .ce 1000 \fI(Remark of Recommendation\ G.222, Volume\ III of the\fR | Red Book, .sp 9p .RT .ce 0 .sp 1P .ce 1000 \fIamended at Geneva, 1964; further amended)\fR .ce 0 .sp 1P .LP \fB1\fR \fBNominal \fR \fBmean power during the busy hour\fR .sp 1P .RT .PP To simplify calculations when designing carrier systems on cables or radio links, the CCITT has adopted a \fIconventional\fR value to represent the \fImean absolute power level\fR (at a zero relative level point) of the speech plus signalling currents, etc., transmitted over a telephone channel in one direction of transmission during the busy hour. .PP The value adopted for this mean absolute power level corrected to a zero relative level point is \(em15\ dBm0 (mean power\ =\ 31.6\ microwatts); this is the mean with time and the mean for a large batch of circuits. .PP \fINote\ 1\fR \ \(em\ This conventional value was adopted by the CCIF in 1956 after a series of measurements and calculations had been carried out by various Administrations between 1953 and 1955. The documentation assembled at the time is indicated in\ [1]. The adopted value of about 32\ microwatts was based on the following assumptions: .RT .LP i) mean power of 10\ microwatts for all signalling and tones (Recommendation\ Q.15\ [2], gives information concerning the apportionment on an energy basis of signals and tones); .LP ii) mean power of 22\ microwatts for other currents, namely: .LP \(em speech currents, including echoes, assuming a mean activity factor of 0.25 for one telephone channel in one direction of transmission; .LP \(em carrier leaks (see Recommendations\ G.232, \(sc\ 5; G.233, \(sc\ 11; G.235, \(sc\ 5); and the Recommendations cited in [3] and\ [4]; .LP \(em telegraph signals, assuming that few telephone channels are used for VF telegraphy systems (output signal power 135\ microwatts (the Recommendation cited in\ [5])) or phototelegraphy (amplitude modulated signal with a maximum signal power of about 1\ milliwatt (the Recommendation cited in\ [6])). .bp .PP On the other hand, the power of pilots in the load of modern carrier systems has been treated as negligible. .PP The reference to \*Qthe busy hour\*U in \(sc\ 1 is to indicate that the limit (of \(em15\ dBm0) applies when transmission systems and telephone exchanges are at their busiest so that the various factors concerning occupancy and activity of the various services and signals are to be those appropriate to such busy conditions. .PP It is not intended to suggest that an integrating period of one hour may be used in the specification of the signals emitted by individual devices connected to transmission systems. This could lead to insupportably high short\(hyterm power levels being permitted which give rise to interference for durations of significance to telephony and other services. .RT .PP \fINote\ 2\fR \ \(em\ The question of reconsidering the assumptions leading to this conventional value arose in 1968 for the following reasons: .LP \(em changes in the r.m.s. power of speech signals, due to the use of more modern telephone sets, to a different transmission plan, and perhaps also to some change in subscriber habits; .LP \(em change in the mean activity factor of a telephone channel due, \fIinter alia\fR , to different operating methods; .LP \(em increase in the number of VF telegraphy bearer circuits and sound\(hyprogramme circuits; .LP \(em introduction of circuits used for data transmission, and rapid increase in their number. .PP During several Study Periods these points have been under study and various Administrations carried out measurements of speech signal power and loading of carrier systems. The results are shown in Supplement No.\ 5. These results indicate that there is no sufficiently firm information to justify an alteration to the conventional mean value of \(em15\ dBm0 (32\ \(*mW0) for the long\(hyterm mean power level per channel. .PP Indeed, the steps envisaged by Administrations to control and reduce the levels of non\(hyspeech signals indicate a tendency to limit the effect of the increase in the non\(hyspeech services. .PP As regards the subdivision of the 32\ \(*mW into 10\ \(*mW signalling and tones and 22\ \(*mW speech and echo, carrier leaks, and telegraphy, again there is no evidence which would justify proposals to alter this subdivision. .PP As a general principle, it should always be the objective of Administrations to ensure that the \fIactual\fR load carried by transmission systems does not significantly differ from the \fIconventional\fR value assumed in the design of such systems. .RT .PP \fINote\ 3\fR \ \(em\ The CCITT has agreed to the following rules concerning the maximum permissible number of VF telegraph bearer circuits: .LP 1) For a \fI12\(hychannel system\fR , both the load capacity and the intermodulation requirements are determined by the statistics of speech; hence there is no reason to limit the number of channels in a 12\(hychannel system which may be used as VF telegraphy bearer channels. .LP 2) For a \fI60\(hychannel system\fR , the load capacity is determined by the statistics of speech but the intermodulation requirements for a mixed VF telegraph and speech loading become controlling when the VF telegraph bearers exceed about 30% of the total. Hence it is possible, without change of specifications, to allow up to 20\ channels in this system to be used for VF telegraphy. .LP 3) For a \fI120\(hychannel system\fR , about 12% of the total could be allowed for VF telegraph bearers. The number of reserve circuits for VF telegraphy is excluded from these limits for both 60\(hy and 120\(hychannel systems. The number of channels for these systems should be distributed more or less uniformly throughout the line\(hyfrequency band. .LP 4) For \fIsystems with 300 or more channels\fR , the CCITT is not yet able to define any specific limit, owing to the many complicated factors such as mean power, peak power, overload capacity, intermodulation, noise\(hyperformance and pre\(hyemphasis, which have to be taken into consideration. .LP 5) For \fIgroups\fR and \fIsupergroups\fR no conclusion could be obtained. From information available, it would be unwise, without special consideration, to exceed two VF telegraph systems per supergroup in a wideband system. .bp .LP 6) For \fItransmission systems not exceeding 1000\ km\fR the permissible number of telegraph systems may be increased if the power per telegraph channel is reduced according to Table\ 1/G.223. .LP A similar table in respect of transmission systems longer than 1000\ km cannot be drawn up at this time. There is evidence to suggest that for systems considerably longer than 1000\ km a reduction in telegraph signal power gives rise to unacceptable levels of telegraph distortion and character error rates. .LP .rs .sp 12P .ad r \fBTable 1/G.223 (maintenu) T1.223, p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP \fB2\fR \fBLoading for calculation of intermodulation noise\fR .sp 1P .RT .PP 2.1 It will be assumed for the calculation of intermodulation noise below the overload point that the multiplex signal during the busy hour can be represented by a uniform spectrum random noise signal, the mean absolute power level of which, at a zero relative flat level point, is given by the following formulae: \v'6p' .sp 9p .RT .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 15 + 10 log \d10 \u\ \fIn\fR ) dBm0 for \fIn\fR \(>=" 240 .ce 0 .sp 1P .LP and .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 1 + 4 log \d10 \u\ \fIn\fR ) dBm0 for 12 \(= \fIn\fR < 240, .ce 0 .sp 1P .LP .sp 1 \fIn\fR | being the total number of telephone channels in the system and \fIP\fR | (\fIn\fR ) the power of the random noise signal in milliwatts. .PP Examples are shown in Table\ 2/G.223 of the results given by these formulae for some typical values of\ \fIn\fR . .LP .rs .sp 10P .ad r \fBTable 2/G.223 (maintenu) T2.223, p.\fR .sp 1P .RT .ad b .RT .PP These results apply only to systems without pre\(hyemphasis and using independent amplifiers for the two directions of transmission. .bp .PP 2.2 For 2\(hywire systems having common amplifiers for the two directions of transmission (\fIn\fR \ +\ \fIn\fR \ systems), it is necessary to assume a different conventional loading. When the relative levels are the same for both directions of transmission the conventional load is given by the following formulae: \v'6p' .sp 9p .RT .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 15 + 10 log \d10 \u 2\fIn\fR ) dBm0 for \fIn\fR \(>=" 120 .ce 0 .sp 1P .LP and .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 1 + 4 log \d10 \u 2\fIn\fR ) dBm0 for 12 \(= \fIn\fR < 120, .ce 0 .sp 1P .LP .sp 1 where .LP \fIP\fR | (\fIn\fR ) is defined in \(sc\ 2.1 above and \fIn\fR | is the number of channels in each direction of transmission. .PP 2.3 When use is made of a call concentrator having the effect of multiplying the number of circuits established on a system by a coefficient \fIa\fR , for the determination of the conventional load, the number of channels should be multiplied by \fIa\fR and the activity coefficient should remain unchanged (see also Note\ 5 below). The following formulae then replace those given in \(sc\ 2.2 above: \v'6p' .sp 9p .RT .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 15 + 10 log \d10 \u \fIan\fR ) dBm0 for \fIan\fR \(>=" 240 .ce 0 .sp 1P .LP and .sp 1P .ce 1000 10 log \d10 \u \fIP\fR | (\fIn\fR )\ =\ (\(em 1 + 4 log \d10 \u \fIan\fR ) dBm0 for 12 \(= \fIan\fR < 240, .ce 0 .sp 1P .LP .sp 1 \fIn\fR | being the total number of telephone channels in the system and \fIP\fR | (\fIn\fR ) the power of the random noise signal in milliwatts. .PP \fINote\ 1\fR \ \(em\ The mean absolute power level of a uniform\(hyspectrum random noise test signal deduced from these formulae may be used in calculating the intermodulation noise on a hypothetical reference circuit, when there is no overloading. It is considered that these formulae give a good approximation in calculating intermodulation noise when \fIn\fR \ \(>="\ 60. For small numbers of channels, however, tests with uniform\(hyspectrum random noise are less realistic owing to the wide difference in the nature of actual and test signals. .PP \fINote\ 2\fR \ \(em\ In view of the conventional character of these calculations, it was not considered useful to take into account the power transmitted for programme transmissions over carrier systems. Moreover, the mean value of 0.25 was assumed for the activity factor of a telephone channel and it was not deemed useful to study any deviations from this mean. .PP \fINote\ 3\fR \ \(em\ Care must be taken in interpreting the results of tests with uniform\(hyspectrum random noise loading, especially in systems in which the dominant noise contribution in certain channels arises from a particular kind of intermodulation product (e.g.\ A\(emB). In such cases, the weighting factor used in relating the performance of the channel to that under real traffic conditions must be carefully determined. The curve given by the transfer function of the network used to define the conventional telephone signal (see Recommendation\ G.227) may be used in this case to determine the weighting factor for the wideband signal. .PP \fINote\ 4\fR \ \(em\ The formulae in \(sc\ 2.2 above for (\fIn\fR \ +\ \fIn\fR ) type 12\(hychannel systems are the same as those given in \(sc\ 2.1 above (4\(hywire systems), assuming that the number of channels is doubled but that there is no correlation between the channel activities in each direction of transmission. For the purposes of this assumption, the fact that in an (\fIn\fR \ +\ \fIn\fR ) system the two directions of transmission of a telephone circuit are not active at the same moment is ignored. Calculations have shown that the resultant error is negligible and in any case is on the safe side. .PP \fINote\ 5\fR \ \(em\ The formulae in \(sc\ 2.3 above are only valid in the case when all channels are equipped with call concentrators. They are not applicable when only some of the channels are equipped with call concentrators, because the distribution of these channels generally will not be uniform over the band of the multiplex signal. .bp .RT .sp 2P .LP \fB3\fR \fBComponent characteristics and levels\fR .sp 1P .RT .PP The values of the characteristics of circuit components and the levels to be used in calculations will be the nominal values. .PP \fINote\fR \ \(em\ When specifying equipments, a reasonable margin should be allowed for the ageing of components and for tolerances on levels, supply voltages, temperature, etc. .RT .sp 2P .LP \fB4\fR \fBPsophometric weights\fR \fBand weighting factor\fR .sp 1P .RT .PP For calculating psophometric power, use should be made of the \fITable of psophometer weighting for commercial telephone circuits\fR which is given in Table\ 4/G.223. .PP If uniform\(hyspectrum random noise is measured in a 3.1\(hykHz band with a flat attenuation/frequency characteristic, the noise level must be reduced by 2.5\ dB to obtain the psophometric power level. For another bandwidth, \fIB\fR , the weighting factor will be equal to: \v'6p' .RT .sp 1P .ce 1000 @ left ( 2.5~+~10~log~\d10~\u~ { fIB\fR } over { .1~kHz } right ) @ dB .ce 0 .sp 1P .LP .sp 1 When \fIB\fR \ =\ 4\ kHz, for example, this formula gives a weighting factor of 3.6\ dB. .sp 2P .LP \fB5\fR \fBCalculating noise in modulating (translating) equipments\fR .sp 1P .RT .PP (See also Recommendation G.230.) .RT .PP 5.1 For group, supergroup, etc., \fImodulating equipments\fR , in calculating \fIintermodulation noise\fR (below the overload point), the following conventional values, already accepted, will be assumed for the load at a\fR zero relative level point: .sp 9p .RT .LP \(em for\ 12\(hychannel\ group modulators: 3.3 dBm0; .LP \(em for\ 60\(hychannel\ supergroup modulators: 6.1 dBm0; .LP \(em for\ 300\(hychannel\ mastergroup modulators: 9.8 dBm0. .PP 5.2 The mean noise power in channel translating equipments due to interference from channels adjacent to the disturbed channel will be calculated as follows. In all the terminal equipment of the hypothetical reference circuit there are six exposures to adjacent\(hychannel disturbance. Five of these disturbing channels will be assumed to carry speech\(hylike loading signals each having a mean power of 32\ \(*mW, i.e. an absolute power level of \(em15\ dBm0 per channel at a zero relative level point, while the sixth disturbing channel will be assumed to carry telegraphy, phototelegraphy or data transmission with a conventional loading of 135\ \(*mW applied at the zero relative level point, i.e. an absolute power of \(em8.7\ dBm0 uniformly distributed over the frequency range\ 380 to\ 3220\ Hz. .sp 9p .RT .PP The conventional telephony signal defined in Recommendation\ G.227 may be used to simulate the speech signals transmitted on the disturbing channels. .PP \fINote\fR \ \(em\ Limitation of crosstalk caused by channels adjacent to the disturbed channel is governed by an additional clause in the channel equipment specification (see Recommendation\ G.232, \(sc\ 9.2). In addition, the power of signalling pulses is restricted by Recommendation\ G.224. .RT .PP 5.3 In all cases allowance should, of course, be made for thermal noise. .sp 9p .RT .sp 2P .LP \fB6\fR \fBOverload point of amplifiers\fR , \fBthe\fR \fBequivalent\fR \fBr.m.s. power of the peak of the multiplex signal\fR \fBand the\fR \fBmargin\fR \fBagainst saturation\fR .sp 1P .RT .sp 1P .LP 6.1 \fBoverload point\fR .sp 9p .RT .PP The overload point or overload level of an\fR amplifier is at that value of absolute power level at the output at which the absolute power level of the third harmonic increases by 20\ dB when the input signal to the amplifier is increased by 1\ dB. .bp .PP This first definition does not apply when the test frequency is so high that the third harmonic frequency falls outside the useful bandwidth of the amplifier. The following definition may then be used: .RT .LP \fISecond definition\fR \ \(em\ The overload point or overload level of an amplifier is 6\ dB higher than the absolute power level in dBm, at the output of the amplifier, of each of two sinusoidal signals of equal amplitude and of frequencies\ A and\ B respectively, when these absolute power levels are so adjusted that an increase of 1\ dB in both of their separate levels at the input of the amplifier causes an increase, at the output of the amplifier, of 20\ dB in the intermodulation product of frequency\ 2A\(emB. .sp 1P .LP 6.2 \fBequivalent r.m.s. sine wave power of the peak of a\fR \fBmultiplex telephone signal\fR .sp 9p .RT .PP This is the power of a sinusoidal signal whose amplitude is that of the peak voltage of the multiplex signal. Figure\ 1/G.223 shows the equivalent peak power level in terms of the number of channels. Up to 1000\ channels, it is derived from Curve\ B, Figure\ 7 of Reference\ [7] taking into account the conventional value (\(em15\ dBm0) allowed by the CCITT for the mean power per channel instead of \(em16\ dBm0, i.e.\ an increase of 1\ dB. Numerical values are given in Table\ 3/G.223. .RT .LP .rs .sp 8P .ad r \fBTable 3/G.223 (maintenu) T3.223, p.\fR .sp 1P .RT .ad b .RT .PP For systems having a capacity higher than 1000 channels, the equivalent peak power level may be derived from the following formula: \v'6p' .sp 1P .ce 1000 10 log \d10 \u \fIP\fR \deq \u = @ left [ \(em5~+~10~log~\d10~\u~\fIn\fR~+~10~log~\d10~\u~ left ( 1~+ { 5 } over { sqrt { fIn\fR } } right ) right ] @ \ dBm0 .ce 0 .sp 1P .LP .sp 1 where .LP \fIP\fR\d\fIe\fR\\d\fIq\fR\u is the equivalent r.m.s. sine wave power in milliwatts and .LP \fIn\fR the number of channels. .PP Table 3a/G.223 gives corresponding numerical values for a few typical numbers of channels. .PP The curve in Figure\ 1/G.223 and the formula for numbers of channels exceeding 1000 are for use when there is no amplitude limiter at the channel input and when there is no pre\(hyemphasis in the overall band of the multiplex signal; other cases are being studied. .PP \fINote\fR \ \(em\ Mathematical models which enable calculations of the equivalent peak power level of multiplex telephone speech signals are described in Supplement No.\ 22 at the end of present fascicle. .RT .sp 1P .LP 6.3 \fBMargin against saturation\fR .sp 9p .RT .PP In planning, a margin of a few decibels should be maintained between the absolute level of the equivalent power of the peak of the multiplex signal and the amplifier saturation point, to allow for level variations, ageing,\ etc. A national practice to estimate the signal load margin of systems and equipments is shown in Supplement No.\ 26. .PP \fIMultiplex signals different from telephony\fR \ \(em\ It is stressed that \(sc\ 6.2 above relates to systems designed for telephony only, i.e. for a channel loading as described in \(sc\ 1 above. It should be realized that when the characteristics of the multiplex signal differ significantly from those assumed in \(sc\ 1 above, additional margins against saturation may be required. .bp .RT .LP .rs .sp 36P .ad r \fBFigure 1/G.223, p.\fR .sp 1P .RT .ad b .RT .ce \fBH.T. [T4.223]\fR .ce TABLE\ 3a/G.223 .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(96p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) . { Number of chanel, \fIn\fR } 1260 1800 2700 3600 10 | 00 _ .T& lw(96p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) . { Equivalent peak power level (dBm0) } 27.5 29 30.5 31.5 36 _ .TE .nr PS 9 .RT .ad r \fBTable 3a/G.223 [T4.223] p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBTable 4/G.223 (maintenu) 1T5.223, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 34P .ad r \fBTable 4/G.223 (maintenu) 2T5.223, p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] \fICCITT collected documents on the volume and power of speech currents\fR \fItransmitted over international telephone circuits\fR , Blue Book, Vol.\ III, Part\ 4, Annex\ 6, ITU, Geneva,\ 1965. .LP [2] CCITT Recommendation \fINominal mean power during the busy hour\fR , Vol.\ VI, Rec.\ Q.15. .LP [3] CCITT Recommendation \fICharacteristics of group links for the\fR \fItransmission of wide\(hyspectrum signals\fR , Vol.\ III, Rec.\ H.14, \(sc\ 2.3. .LP [4] CCITT Recommendation \fICharacteristics of supergroup links for the\fR \fItransmission of wide\(hyspectrum signals\fR , Vol.\ III, Rec.\ H.15, \(sc\ 2.3. .LP [5] CCITT Recommendation \fIBasic characteristics of telegraph equipments\fR \fIused in international voice\(hyfrequency telegraph systems\fR , Vol.\ III, Rec.\ H.23, \(sc\ 1.2. .LP [6] CCITT Recommendation \fIPhototelegraph transmissions on telephone\(hytype\fR \fIcircuits\fR , Vol.\ III, Rec.\ H.41, \(sc\ 2.3. .LP [7] HOLBROOK (B. | .) and DIXON (J. | .): Load Rating Theory for Multichannel Amplifiers, \fIBell System Technical Journal\fR , \fB18\fR , No.\ 4, pp.\ 624\(hy644, October\ 1939. .bp .sp 2P .LP \fBRecommendation\ G.224\fR .RT .sp 2P .ce 1000 \fBMAXIMUM\ PERMISSIBLE\ VALUE\ FOR\ THE\ \fR \fBABSOLUTE\ POWER\ LEVEL\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.224'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.224 %' .ce 0 .sp 1P .ce 1000 \fB(POWER\ REFERRED\ TO\ ONE\ MILLIWATT)\ OF\ A\ SIGNALLING | fR \fBPULSE\fR .FS This Recommendation is the same as Recommendation Q.16\ [1]; it applies both to national and to international signalling systems. .FE .ce 0 .sp 1P .PP The CCITT recommends that, for crosstalk reasons, the absolute power level of each component of a short duration signal should not exceed the values given in Table\ 1/G.224. .sp 1P .RT .LP .rs .sp 18P .ad r \fBTable 1/G.224 (maintenu) T1.224, p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCITT Recommendation \fIMaximum permissible value for the absolute\fR \fIpower level of a signalling pulse\fR , Vol.\ VI, Rec.\ Q.16. \v'6p' .sp 2P .LP \fBRecommendation\ G.225\fR .RT .sp 2P .sp 1P .ce 1000 \fBRECOMMENDATIONS\ RELATING\ TO\ THE\ \fR \fBACCURACY\ OF | fR \fBCARRIER\ FREQUENCIES\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.225'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.225 %' .ce 0 .sp 1P .ce 1000 \fI(amended at Geneva, 1964, and Mar del Plata, 1968)\fR .sp 9p .RT .ce 0 .sp 1P .LP \fB1\fR \fBAccuracy of the virtual carrier frequencies on an international circuit or on a chain of circuits\fR .sp 1P .RT .PP As the channels of any international telephone circuit should be suitable for voice\(hyfrequency telegraphy, the accuracy of the virtual carrier frequencies should be such that the difference between an audio\(hyfrequency applied to one end of the circuit and the frequency received at the other end should not exceed 2\ Hz, even when there are intermediate modulating and demodulating processes. .bp .PP To attain this objective, the CCITT recommends that the channel and group carrier frequencies of the various stages should have the following accuracies: .RT .ad r Virtual channel carrier frequencies in group \(+- | 0\uD\dlF261\u6\d .PS 10 \ \ .ad b .RT .ad r Group and supergroup carrier frequencies \(+- | 0\uD\dlF261\u7\d .PS 10 \ \ .vs +2p .RT .ad b .RT .PP Mastergroup and supermastergroup carrier frequencies: .ad r \(em for the 12\(hyMHz system \(+- | | (mu | 0\uD\dlF261\u8\d .PS 10 .ad b .RT .ad r \(em for the 60\(hyMHz system (above 12 MHz) \(+- | 0\uD\dlF261\u8\d .PS 10 \ \ .vs +2p .RT .ad b .RT .PP Experience shows that, if a proper check is kept on the operation of oscillators designed to these specifications, the difference between the frequency applied at the origin of a telephone channel and the reconstituted frequency at the other end hardly ever exceeds 2\ Hz if the channel has the same composition as the 2500\(hykm hypothetical reference circuit for the system concerned. .PP Calculations indicate that, if these recommendations are followed, in the 4\(hywire chain forming part of the hypothetical reference connection defined in Figure\ 1/G.103 .FS In fact, the chain considered for these calculations comprised 16 (instead of 12) modulator/demodulator pairs to allow for the possibility that submarine cables with equipments in conformity with Recommendation\ G.235 might form part of the chain. No allowance was made, however, for the effects of Doppler frequency\(hyshift due to inclusion of a non\(hystationary satellite; values for this shift are given in CCIR Report\ 214\ [2]. .FE there is about 1% probability that the frequency difference between the beginning and the end of the connection will exceed 3\ Hz and less than 0.1% probability that it will exceed 4\ Hz. .PP \fINote\ 1\fR \ \(em\ In small stations, i.e. in stations which do not need supergroup carrier frequencies, the accuracy of the group carrier may be \(+- | 0\uD\dlF261\u6\d, which is the same as for channel carrier frequencies. .PP \fINote\ 2\fR \ \(em\ The modulating frequencies appropriate to (\fIn\fR \ +\ \fIn\fR ) systems should have the accuracies recommended in the relevant Recommendations: .RT .LP Recommendation\ G.311 for 12\(hychannel open\(hywire systems; .LP Recommendation\ G.361 for 3\(hychannel open\(hywire systems; .LP Recommendations\ G.326 and G.327\ [3] for (12\ +\ 12) cable systems. .sp 2P .LP \fB2\fR \fBMeasure of alignment of the master oscillators\fR .sp 1P .RT .PP The recommendation in \(sc\ 1 above cannot be met without some measure of alignment of the master oscillators at the various stations in which modulation occurs. .PP Carrier\(hytransmission systems are formed into \*Qpartial networks\*U extending over the whole or a part of a country. Synchronization of the master oscillators of a partial network is ordinarily based on national frequency comparisons; international comparisons may be made if necessary. .RT .sp 1P .LP 2.1 \fINational frequency comparisons\fR .sp 9p .RT .PP It is necessary that, within the same partial network of coaxial carrier systems, the master oscillators in stations where frequencies are generated should be \*Qcoordinated\*U. This \*Qcoordination\*U can consist of a control of one oscillator with respect to another to give one of the following three conditions: .RT .LP 1) synchronization, i.e. identical frequency and fixed phase relationship; .LP 2) isochronization, i.e. identical frequency only; .LP 3) differential control to correct differences between the frequencies at intervals. .PP Also, automatic devices can be used to give an alarm if the difference in frequency between the checking pilot and a local oscillator exceeds a certain fixed value. .PP The CCITT has not recommended any particular method of comparing or controlling the master oscillators at different stations, and \*Qroutine frequency comparison\*U of the master oscillators may be thought sufficient; this comparison being followed if necessary by automatic or manual regulation, the master oscillators in each partial network being compared periodically with a national frequency standard, if possible. .bp .PP The routine comparison of the frequencies generated by the master oscillators is made by means of a \*Qfrequency check pilot\*U transmitted to line for this purpose. It is not necessary to compare phases. .RT .sp 1P .LP 2.2 \fIInternational frequency comparisons\fR .sp 9p .RT .PP The case may arise, either of a country that has a national frequency standard with no facilities for distributing it throughout the country (particularly in an area in which a coaxial carrier system is to be set up), or of a country that has no national frequency standard. Recommendation\ M.540\ [4], describes methods by which such countries may obtain a standard frequency by radio, or may have a controlled frequency sent over a telephone circuit. .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fIHypothetical reference connections\fR , Vol. III, Rec.\ G.103, Figure\ 1/G.103. .LP [2] CCITT Report \fIThe effects of doppler frequency\(hyshifts and switching\fR \fIdiscontinuities in the fixed satellite service\fR , Vol.\ IV, Report\ 214, Dubrovnik,\ 1986. .LP [3] CCITT Recommendation \fIValve\(hytype systems offering 12 telephone\fR \fIcarrier circuits on a symmetric cable pair [(12\ \fR +\fI\ 12) systems]\fR , Orange Book, Vol.\ III\(hy1, Rec.\ G.327, ITU, Geneva, 1977. .LP [4] CCITT Recommendation \fIRoutine maintenance of carrier and pilot\fR \fIgenerating equipment\fR , Vol.\ IV, Rec.\ M.540. \v'1P' .sp 2P .LP \fBRecommendation\ G.226\fR .RT .sp 2P .sp 1P .ce 1000 \fBNOISE\ ON\ A\ REAL\ LINK\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.226'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.226 %' .ce 0 .sp 1P .LP \fB1\fR \fBCable systems\fR .sp 1P .RT .PP It should be appreciated that designers are usually concerned, not with particular circuits or links, but with plant that will be used for the establishment of many links. It is not practicable for the CCITT to specify the performance of every real link that may be established, or for the designer to contemplate changing his design to suit the various lengths or other conditions on different real links. The CCITT has therefore defined hypothetical reference circuits, so that designers can be sure that, if their particular design of plant is used throughout a real circuit made up in the same way as a hypothetical reference circuit, the performance specified by the CCITT for the hypothetical reference circuit will be realized on that real circuit. .PP A real international link usually has a different make\(hyup from that of the hypothetical reference circuit, and often includes equipments of different design. For each of these two reasons the performance to be expected from real links cannot be deduced uniquely from the Recommendations relative to hypothetical reference circuits. .PP However, on a real homogeneous section it must be expected that the noise power measured at the time of commissioning, and with a conventional load as defined in \(sc\ 2 of Recommendation\ G.223, will be about the same as that calculated taking into account the particular composition of the real homogeneous section and the real parameters as well as the implications of Recommendation\ G.222, \(sc\ 2.6. There should be no cause for anxiety unless the measured noise power exceeds the calculated power by an appreciable amount, which might indicate a fault somewhere in the equipment. In such a case, every effort should be made to reduce the measured noise power to a value of the same order as that calculated. .RT .sp 2P .LP \fB2\fR \fBRadio links\fR .sp 1P .RT .PP See CCIR Recommendation\ 395\ [1]. .bp .RT .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCIR Recommendation \fINoise in the radio portion of circuits to be\fR \fIestablished over real radio\(hyrelay links for FDM telephony\fR , Vol.\ IX, Rec.\ 395, Dubrovnik,\ 1986. \v'2P' .sp 2P .LP \fBRecommendation\ G.227\fR .RT .sp 2P .sp 1P .ce 1000 \fBCONVENTIONAL\ TELEPHONE\ SIGNAL\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.227'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.227 %' .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1964; amended at Mar del Plata, 1968)\fR .sp 9p .RT .ce 0 .sp 1P .LP \fB1\fR \fBPrinciple\fR .sp 1P .RT .PP For the calculation or measurement of crosstalk noise between adjacent channels and, generally speaking, when it is desired to simulate the speech currents transmitted by a telephone channel .FS Care is needed in applying this conventional signal to simulate speech loading, since the statistics of a Gaussian noise signal and of real speech are different. A speech\(hysimulating generator for loading purposes is given in\ [1]. .FE , the CCITT recommends that a conventional telephone signal be used, the main characteristic of which is a shaping network as a function of the frequency. .PP This network is defined by the following transfer coefficient as a function of the frequency: .RT .LP .rs .sp 12P .ad r \fBFigure 1/G.227, p.\fR .sp 1P .RT .ad b .RT .sp 1P .ce 1000 @ { fIE\fR~ | } over { ~\fIV\fR~ | } @ = @ { 8400~+~91238~\fIp\fR~\u2\d~+~11638~\fIp\fR~\u4\d~+~\fIp\fR (67280~+~54050~\fIp\fR~\u2\d) } over { 00~+~4001~\fIp\fR~\u2\d~+~\fIp\fR~\u4\d~+~\fIp\fR (36040~+~130~\fIp\fR~\u2\d) } @ .ce 0 .sp 1P .ce 1000 .sp 1 where \fIp\fR = j @ { fIf\fR (Hz) } over { 000~Hz } @ , \fIE\fR and \fIV\fR are defined by Figure 1/G.227. .ce 0 .sp 1P .PP .sp 1 The response curve of the network is shown in Figure\ 2/G.227, and an example of the design is given in Figure\ 3/G.227 with relevant values. .LP .sp 2 .bp .LP .rs .sp 22P .ad r \fBFigure 2/G.227, p.\fR .sp 1P .RT .ad b .RT .LP .rs .sp 25P .ad r \fBFigure 3/G.227, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP \fB2\fR \fBExample of network design\fR .sp 1P .RT .PP The network is made up of three bridged\ \fIT\fR sections with a constant characteristic impedance equal to \fIR\fR\d0\u\ ohms. .PP Figure 3/G.227 represents the network and indicates the values of the various components normalized to\ \fIR\fR\d0\u. .PP A tolerance of \(+- | % can be allowed on the value of each component. .PP \fINote\fR \ \(em\ If \(*h\d1\u, \(*h\d2\u, \(*h\d3\uare the \*Qcomposite\*U transfer coefficients of sections\ 1, 2 and 3 respectively, we have: \v'6p' .RT .LP .sp 1 .sp 1P .ce 1000 @ { fIE\fR~ | } over { ~\fIV\fR~ | } @ = \fIe\fR \u\\d(*h = \fIe\fR \u\(*h 1 +\(*h 2 +\(*h 3 \d .ce 0 .sp 1P .LP .sp 1 with\ \ \fIe\fR \u\(*h 1 \d = @ { 6~+~90\fIp\fR~+~46\fIp\fR~\u2\d } over { ~+~90\fIp\fR~+~\fIp\fR~\u2\d } @ .LP .sp 1 with\ \ \fIe\fR \u\(*h 2 \d = @ { 0~+~11\fIp\fR } over { 0~+~\fIp\fR } @ .LP .sp 1 with\ \ \fIe\fR \u\(*h 3 \d = @ { 0~+~23\fIp\fR } over { 0~+~\fIp\fR } @ .LP .sp 1 with\ \ \fIp\fR = j @ { fIf\fR (Hz) } over { 000~Hz } @ .LP .sp 2 .PP Composite loss equals the insertion loss in this particular case since the source and the load impedances are equal. .FE The minimum composite loss of the complete network lies in the vicinity of 600\ Hz and equals \fIa\fR\d0\u\ ~\ 2.9\ dB for this example. .PP The curve in Figure\ 2/G.227 represents, as a function of frequency, the composite loss of the network in Figure\ 3/G.227 relative to the minimum loss\ \fIa\fR\d0\u. .RT .sp 2P .LP \fB3\fR \fBSignal at the network input\fR .sp 1P .RT .PP The network may be energized either by a uniform\(hyspectrum random noise signal or by a closely spaced harmonic series. In the latter case, the following precautions are necessary: .RT .LP 1) Spacing of the harmonics should not exceed 50\ Hz. .LP 2) The measuring instrument must have an adequate integrating time with respect to the fundamental period of the harmonic series. Types of CCITT instruments in general use, such as the psophometer, are believed to be satisfactory in this respect. .LP 3) The peak/r.m.s. ratio of the signal should not exceed 3.5. This requirement may be achieved, in the case of a particular generator, by means of an associated phase\(hychanging network. .LP 4) The energizing signals (uniform\(hyspectrum random noise and harmonic series) could lead to different results for subjective, e.g. aural assessments at the receiving end, and such measurements should not, therefore, involve the use of the conventional telephone signal generator. That apparatus would be used solely for objective measurements, in which a psophometer served as measuring instrument. .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCITT \(em Question 5/C, Annex\ 2, Green Book, Vol.\ III, ITU, Geneva,\ 1973. .LP .sp 1 .bp .sp 2P .LP \fBRecommendation\ G.228\fR .RT .sp 2P .ce 1000 \fBMEASUREMENT\ OF\ \fR \fBCIRCUIT\ NOISE\ IN\ CABLE\ SYSTEMS\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.228'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.228 %' .ce 0 .sp 1P .ce 1000 \fBUSING\ A\ UNIFORM\(hySPECTRUM\ RANDOM\ NOISE\ LOADING\fR .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1964; further amended)\fR .sp 9p .RT .ce 0 .sp 1P .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering that\fR .sp 9p .RT .PP (a) it is desirable to measure the performance of cable systems for frequency\(hydivision multiplex telephony under conditions closely approaching those of actual operation; .PP (b) a signal with a continuous uniform spectrum (white noise) has statistical properties similar to those of a multiplex signal when the number of channels is not too small; .PP (c) the use of a signal with a continuous uniform spectrum to measure the performance of such cable systems is already widespread; .PP (d) it is necessary to standardize the frequencies and bandwidths of the measuring channels to be used for such measurements; .PP (e) for reasons of international compatibility it is necessary to standardize the minimum attenuation and the bandwidth of the stop filters which may have to be used in the white\(hynoise generator; .PP (f ) the CCITT has indicated, for the planning of telephone circuits, a mean value of signal power in the baseband of a multiplex telephone system to be taken into consideration during the busy hour (Recommendation\ G.223), .sp 2P .LP \fIrecommends that\fR .sp 1P .RT .PP \fB1\fR The performance of frequency\(hydivision multiplex cable systems should be measured by means of a signal with a continuous uniform spectrum in the frequency band used for the telephone channels. .sp 9p .RT .PP \fB2\fR The nominal power level of the uniform spectrum test signal should be in accordance with the conventional load, specified in Recommendation\ G.223. If applied at the point of interconnection of the system corresponding to \fIT\fR ` of Recommendation\ G.213, the absolute power levels of interest are shown in column\ 4 of Table\ 1/G.228. .sp 9p .RT .PP 2.1 The sending equipment should be capable of providing, at the output of an inserted bandstop filter, a loading level at least up to +10\ dB relative to the nominal power level defined above. .PP 2.2 Within the bandwidth corresponding to the baseband of the system under test, the r.m.s. voltage of the white noise spectrum measured in a band of about 2\ kHz should not vary by more than \(+- | .5\ dB. This degree of spectrum uniformity should be met in the level range up to +6\ dB relative to the nominal power level, indicated in Table\ 1/G.228, column\ 4. .PP 2.3 The white noise test signal should be available at the output of the sending equipment with a peak factor of about 12\ dB with respect to the r.m.s. value. .PP \fB3\fR The nominal effective cut\(hyoff frequencies (the cut\(hyoff frequencies of hypothetical filters having ideal square cut\(hyoff characteristics and transmitting the same power as the real filters) and tolerances for the bandpass filters proposed for the various bandwidths of systems to be tested, should be as specified in Table\ 2/G.228. To reduce the number of filters required, compromises have been made between the nominal effective cut\(hyoff frequency and the system bandwidth\(hylimiting frequency in some cases. The tolerances ensure that consequent calibration errors do not exceed \(+- | .1\ dB and errors in measurement of intermodulation noise do not exceed \(+- | .2\ dB assuming system pre\(hyemphasis of about 10\ dB. .bp .sp 9p .RT .LP .rs .sp 24P .ad r \fBTable 1/G.228 (maintenu) T1.228, p.\fR .sp 1P .RT .ad b .RT .LP .rs .sp 25P .ad r \fBTable 2/G.228 (maintenu 1 corr. par Montage) T2.228, p.\fR .sp 1P .RT .ad b .RT .LP .bp .PP 3.1 The discrimination of a lowpass filter should be at least 20\ dB at a frequency more than 10% above nominal cut\(hyoff and at least 25\ dB at frequencies more than 20% above nominal cut\(hyoff. The discrimination of a highpass filter should be at least 25\ dB at frequencies more than 20% below nominal cut\(hyoff. .PP 3.2 To limit discrimination against measuring channels, the spread of losses introduced by any pair of highpass and lowpass filters should not exceed 0.2\ dB over a range of frequencies which includes the upper and lower measuring channels. .PP \fB4\fR Values of the characteristics for the discrimination in each stop\(hyband at the output of a sending equipment are given in Table\ 3/G.228. These characteristics are intended to apply over a temperature range from 10 | (deC to\ 40 | (deC; .sp 9p .RT .PP \fB5\fR When the receiving equipment is connected directly to a sending equipment provided with bandstop filters which only just meet the requirements of \(sc\ 4\ above, the ratio of the noise power indicated by the receiving equipment when the bandstop filter is bypassed, to that indicated when the filter is in circuit, should be a minimum of 67\ dB; this requirement applies when a conventional load is applied. The minimum effective bandwidth of the receiver should be 1.7\ kHz; the maximum reading of absolute noise power arising from leakage given by a receiver of 1.74\ kHz effective bandwidth and which just meets the foregoing leakage requirement is \(em85.6\ dBm0p. .sp 9p .RT .PP \fB6\fR Additional measuring channels may be provided by agreement between the Administrations concerned. .sp 9p .RT .PP \fINote\fR \ \(em\ In Annexes\ A and\ B some general information is given on the measuring procedures, the choice of filter characteristics, correction methods and accuracy objectives. .LP .rs .sp 32P .ad r \fBTable 3/G.228 (maintenu 1 corr. par Montage) T3.228, p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation\ G.228) .sp 9p .RT .ce 0 .ce 1000 \fBOutline of the \fR \fBwhite noise measuring method\fR .sp 1P .RT .ce 0 .LP A.1 \fIGeneral principle\fR .sp 1P .RT .PP The principal components of the measuring setup are shown in Figure\ A\(hy1/G.228. .RT .LP .rs .sp 22P .ad r \fBFigure A\(hy1/G.228, p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP A.2 \fIMeasuring procedures\fR .sp 9p .RT .PP Two methods for assessing the noise performance of a transmission system are in widespread use: .RT .sp 1P .LP A.2.1 \fIMeasurement of noise power ratio (NPR)\fR .sp 9p .RT .PP The noise power ratio \v'6p' .RT .ce 1000 NPR = 10 log @ { fIW~\dA\u\fR~ | } over { fIW~\dB\u\fR~ | } @ dB = ?63\fIa\fR .ce 0 .ad r (A\(hy1) .ad b .RT .LP \v'7p' .sp 1 is measured at various levels of\ \fIP\fR\d\fIs\fR\u. The r.m.s. level meter serves as an indicator only. The value\ \fIW\fR\d\fIA\fR\uis the noise power in the measuring channel without taking account of the effect of frequency gaps between groups of channels in actual operation. .bp .PP In an \fIN\fR \(hychannel system the following definitions are introduced: .LP \fIP\fR\d\fIs\fR\u = \fIN\fR | (mu | fIP\fR\d\fIC\fR\\d\fIH\fR\u .LP \fIP\fR\d\fIC\fR\\d\fIH\fR\u = variable signal power per channel .LP \fIp\fR\d\fIC\fR\\d\fIH\fR\u = \(em15\ dBm0\ +\ ?63\fIp\fR \ =\ load level per channel .LP \(em15\ dBm0 is the conventional load per channel according to Recommendation\ G.223 for systems with \fIN\fR \ \(>="\ 240 | (mu | 63\fIp\fR \ (dB) is the excess load relative to \(em15\ dBm0 .LP \fIp\fR\d\fIn\fR\u = weighted noise power level (dBm0p) measured at point\ \fIT\fR in a 3.1\ kHz telephone channel. .PP The measured NPR values are usually plotted, as shown in Figure\ A\(hy2/G.228, as a function of the excess channel loading\ ?63\fIp\fR . .LP .rs .sp 20P .ad r \fBfigure A\(hy2/G.228, p.\fR .sp 1P .RT .ad b .RT .PP The relation between NPR values measured on a channel and the weighted noise power level referred to a zero relative level point is: .ad r \fIp\fR\d\fIn\fR\u = (\(em\ NPR\ \(em\ 18.6\ \(em\ 10\ log\ k\ +\ ?63\fIp\fR ) dBm0p (A\(hy2) .vs +2p .RT .ad b .RT .LP k = \fIB\fR /4\fIN\fR \ (\fIB\fR in kHz) is a correction factor which takes account of the effect of the frequency gaps between groups of channels in the transmission system. .PP Table\ A\(hy1/G.228 gives examples of the correction for some N\(hychannel systems: .ce \fBH.T. [T4.228]\fR .ce TABLE\ A\(hy1/G.228 .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . \fIN\fR 300 960 2700 10 | 00 _ .T& cw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . 10 log k (dB) 0.14 0.22 0.46 1.08 _ .TE .nr PS 9 .RT .ad r \fBtable A\(hy1/G.228 [T4.228], p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP A.2.2 \fIDirect measurement of weighted noise power level\fR .sp 9p .RT .PP With the particular choice of the effective receiver bandwidth .RT .LP ?63\fIf\fR \ =\ 1.74\ kHz (=\ 3.1\ kHz | (mu | 0 \s6\(em0.25 .PS 10 ), .RT .LP the weighted noise power\ \fIP\fR\d\fIn\fR\uin a telephone channel is: .LP \fIP\fR\d\fIn\fR\u\ =\ \fIW\fR\d\fIB\fR\u(see Figure\ A\(hy1/G.228) .LP and the weighted noise level\ \fIp\fR\d\fIn\fR\ureferred to a point of zero relative level becomes: \v'6p' .ce 1000 \fIp \dn\u\fR = @ left [ 10~log~ { fIW~\dB\u\fR } over { ~mW } +~\fIn\fR~\d2\u (dBr) right ] @ dBm0p .ce 0 .ad r (A\(hy3) \v'7p' .ad b .RT .PP .sp 1 In this case the receiver (component\ 7 of Figure\ A\(hy1/G.228) must be a calibrated power level meter. .sp 1P .LP A.3 \fIExamples of investigations using the white noise measuring\fR \fImethod\fR .sp 9p .RT .PP Two kinds of investigations can be made on a system (with length\ \fIL\fR ) between flat relative level points\ \fIT\fR ` and\ \fIT\fR . The one [case\ a)] investigates the effect on the noise performance of load deviations at the input of the system, whereas the other [case\ b)] indicates the influence of level misalignments along the transmission line: .RT .LP a) The test signal noise power\ \fIP\fR\d\fIs\fR\uis varied and the weighted noise level\ \fIp\fR\d\fIn\fR\uis determined in dBm0p. The result is plotted as indicated in Figure\ A\(hy3/G.228. .LP Alternatively to the indication of the noise level for system length\ \fIL\fR in dBm0p, the noise power could have been indicated in pW0p/km. .LP .rs .sp 29P .ad r \fBfigure A\(hy3/G.228, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP b) The relative levels on the transmission line are varied by insertion of attenuators \(em?63\fIn\fR and\ +?63\fIn\fR at the input and output of the system as is illustrated in Figure\ A\(hy4/G.228 which is an excerpt of Figure\ A\(hy1/G.228. .LP .rs .sp 8P .ad r \fBfigure A\(hy4/G.228, p.\fR .sp 1P .RT .ad b .RT .PP The test signal noise power\ \fIP\fR\d\fIs\fR\uis set to the conventional value (\(em15\ dBm0/4\ kHz) at point\ \fIT\fR ` and is kept constant. The noise power level in the measuring channel is determined at point\ \fIT\fR as a function of the relative level at the repeater output, for example. The result is plotted as shown in Figure\ A\(hy5/G.228. .LP .rs .sp 17P .ad r \fBfigure A\(hy5/G.228, p.\fR .sp 1P .RT .ad b .RT .ce 1000 ANNEX\ B .ce 0 .ce 1000 (to Recommendation G.228) .sp 9p .RT .ce 0 .ce 1000 \fBMeasuring accuracy considerations affecting\fR .sp 1P .RT .ce 0 .ce 1000 \fBthe design of the measuring equipment\fR .ce 0 .LP B.1 \fIIntroduction\fR .sp 1P .RT .PP The Recommendations relating to the measurement of circuit noise in systems artificially loaded with uniform spectrum random noise simulating FDM telephone signals were agreed after carefully coordinated studies by three CCI Study Groups concerned. The different Recommendations provided for the application of the white noise measuring method to cable systems (CCITT Recommendation\ G.228), radio\(hyrelay systems (CCIR Recommendation\ 399\ [1]), satellite systems (CCIR Recommendation\ 482\ [2]) and translating equipments (CCITT Recommendation\ G.230). The objective of the coordination was that the separately recommended measuring equipments should conform with common measuring accuracy objectives and, as far as possible, be compatible and interchangeable. .bp .PP The overall accuracy objective of the measuring equipment when used for routine maintenance measurements is \(+- | \ dB. A higher accuracy of about \(+- | \ dB is desirable when measurements are made for the purpose of assessing the noise performance of a system in relation to required performance. This can be achieved by following certain procedures and applying corrections as described in B.4\ and B.5\ below. .PP This Annex states how certain characteristics of measuring equipments were related to measuring accuracy objectives; any future extensions of the Recommendations to provide for measurements on new transmission systems, as yet unstandardized, should take account of those relationships. .RT .sp 2P .LP B.2 \fIBandstop filters\fR .sp 1P .RT .sp 1P .LP B.2.1 \fIChoice of centre frequencies\fR .sp 9p .RT .PP In all cases the choice of nominal centre frequencies of band\(hyelimination filters (i.e. of measuring channels) should take account of the need to minimize the combined discrimination of the pair of bandpass filters used when the bandstop filter provides a lower or upper measuring channel. Therefore, as a rule the centre frequency of a lower measuring channel should be at least 15%\ above the effective cut\(hyoff frequency of the highpass filter and the centre frequency of an upper measuring channel should be more than approximately 5%\ below the cut\(hyoff frequency of the lowpass filter involved. Under \(sc\ 3.2 of the text of this Recommendation it is prescribed that \*Qthe spread of losses introduced by any pair of highpass and lowpass filters should not exceed 0.2\ dB over a range of frequencies which includes the outer measuring channels\*U. .RT .sp 1P .LP B.2.2 \fILeakage\fR .sp 9p .RT .PP The discrimination of a bandstop filter in the neighbourhood of the centre frequency determines, jointly with the receiver selectivity the smallest noise\(hyto\(hysignal ratio that can be measured accurately, i.e. the \*Qleakage\*U effect. The bandstop filter discrimination of 70\ dB (Table\ 3/G.228) results in a ratio of the order of \(em67\ dB being measured when the noise is actually negligible. Leakage effect in the receiver is adequately limited by requiring (see \(sc\ 5 in the text of the Recommendation) that the NPR value should be a minimum of 67\ dB when connected directly to a send equipment with bandstop filters which only just meet the discrimination requirements of Table\ 3/G.228 and when a conventional load of \(em15\ dBm0/4\ kHz is applied. .PP \fINote\fR \ \(em\ According to Formula (A\(hy2) of Annex\ A this value of NPR\ =\ 67\ dB corresponds to a residual noise level of \(em85.6\ dBm0p (i.e.\ 2.8\ pW0p) at the most. .RT .sp 1P .LP B.2.3 \fIEffective bandwidth\fR .sp 9p .RT .PP The basic requirement for the stopband is the condition that the discrimination should be at least 70\ dB in a bandwidth of at least 3\ kHz. The effective bandwidths (approximately the 3\(hydB points) recommended in Table\ 3/G.228 have been found to be technically feasible and lie in the order of 5% or less of the system bandwidth with coil\(hycapacitor type filters and are less than 0.5% with crystal\(hytype filters. It would present economic difficulties to reduce the relative bandwidth of the coil\(hytype filters or to increase the relative bandwidth of the crystal\(hytype filters. .RT .sp 1P .LP B.2.3.1 \fIThird order nonlinearity products\fR .sp 9p .RT .PP The attenuation of the noise loading signal in the vicinity of the measuring channel introduced by a bandstop filter causes an under\(hyindication reading, erring on the low side, of third order nonlinearity noise power in that measuring channel. This under\(hyindication is directly proportional to the effective bandwidth of the elimination filter. .PP Assuming that procedures B.4.3\ and B.4.4\ below are both observed, the under\(hyindication of third order products in a system using no pre\(hyemphasis is about 0.05\ dB for a top measuring channel filter, the effective bandwidth of which is 1% of the system bandwidth. The error associated with a particular filter is at its maximum when the filter provides the top measuring channel of a system. When the same filter is used in wider band systems (thus corresponding to an intermediate measuring channel of the system) its bandwidth is a smaller proportion of the system bandwidth and the associated error is smaller. .PP When pre\(hyemphasis is used but total signal power is unchanged the error is increased by the ratio of the signal density near the measuring channel of the pre\(hyemphasized system to that of the system without pre\(hyemphasis. .bp .PP The effective bandwidths of crystal\(hytype bandstop filters are so small that their effect on measurement errors is negligible. .PP The recommended effective bandwidths for coil\(hycapacitor bandstop filters (Table\ 3/G.228) are such that the under\(hyindication of third order nonlinear noise powers, when the filters provide top measuring channels of systems without pre\(hyemphasis, falls in the range 0.25\ to 0.30\ dB. This range of errors becomes 0.60\ to 0.90\ dB for systems emphasized by 8\ to 10\ dB as is the case in FDM radio\(hyrelay systems (CCIR Recommendation\ 275\ [3]) or in wideband systems on coaxial cables. .RT .sp 1P .LP B.2.3.2 \fISecond order nonlinearity products\fR .sp 9p .RT .PP In long transmission systems third order nonlinearity products normally form a more significant proportion of the total system noise than those of second order. For this reason the recommended maximum effective bandwidths of bandstop filters have been determined on the basis of accuracy objectives for the measurement of third order nonlinearity products. .PP Nevertheless, measuring equipments may still be used for investigations of cases where second order nonlinearity products dominate. Corrections for known filter bandwidths may be made on the following basis: .RT .LP a) Again assuming that procedures B.4.3\ and B.4.4\ below are observed, the error in a reading of second order nonlinearity products introduced by the bandstop filter is an excess reading, rather than the under\(hyindication in the case of third order nonlinearity products. .LP b) The excess reading is directly proportional to the effective bandwidth of the bandstop filter expressed as a percentage of the system bandwidth. The approximate proportionality, assuming no system pre\(hyemphasis: .LP \(em for measuring channels located near the lower limit of the system bandwidth, an effective bandwidth of\ 1% system bandwidth causes an excess reading of 0.05\ dB for second order intermodulation noise power; .LP \(em for measuring channels located in the middle, or near the upper limit, of the system bandwidth, an effective bandwidth of\ 1% system bandwidth causes an excess reading of 0.1\ dB. .LP c) The effect of system pre\(hyemphasis in the case of a bandstop filter near the lower limit of the system bandwidth, i.e.\ where the density of second order nonlinearity products tends to be greatest, is to reduce the error attributable to a given filter bandwidth in the same proportion that the signal density at that frequency is reduced by pre\(hyemphasis. .sp 1P .LP B.3 \fIBandpass filters\fR .sp 9p .RT .PP In order to reduce the number of different filters, compromises have been made in some cases between the nominal effective cut\(hyoff frequency and the system bandwidth limiting frequency (cf. \(sc\ 3 of the text). .PP For the larger systems there may also be a significant difference between the frequency bandwidth 4\fIN\fR \ kHz (\fIN\fR \ being the system capacity expressed in telephone channels) and the system bandwidth (Table\ 2/G.228). .PP Both these facts are taken into account by the correction factor\ k introduced in equation\ (A\(hy2) of Annex\ A and in Table\ A\(hy1/G.228. .PP The recommended tolerances on the nominal values of cut\(hyoff frequencies are such that the actual and nominal bandwidths of the signal load cannot differ by more than\ 1%. This ensures that calibration errors (in NPR measurements) due to this particular imperfection do not exceed about\ 0.05\ dB. .PP The tolerances on the effective lowpass cut\(hyoff frequencies are in all cases less than\ 1.0% of the nominal system bandwidth and in most cases less than\ 0.8%. A difference of\ 0.8% leads to an error, in third order nonlinearity noise measurement, of\ 0.1\ dB, this allowing for a pre\(hyemphasis of\ 8\ dB. Even allowing for a greater degree of pre\(hyemphasis, the maximum error from this cause should not exceed 0.15\ dB. .bp .RT .sp 2P .LP B.4 \fIProcedures for high accuracy measurements\fR .sp 1P .RT .PP The following measuring procedures are recommended for high accuracy type of measurements, for example checks that transmission system noise performance objectives are being achieved. .RT .sp 1P .LP B.4.1 \fISignal load adjustment\fR .sp 9p .RT .PP The loading power should be adjusted to the nominal value by means of a true r.m.s. level measuring device. The maximum error, including reading error, should not exceed \(+- | .15\ dB. .RT .sp 2P .LP B.4.2 \fIReceiver calibration\fR .sp 1P .RT .PP B.4.2.1 Using the NPR method (\(sc\ A.2.1) the receiver should be set with reference to the received signal immediately before insertion of a bandpass filter. .sp 9p .RT .PP B.4.2.2 Using the direct noise power measuring method (\(sc\ A.2.2) the receiver calibration error could be decreased to \(+- | .15\ dB at the particular measuring slot by checking the reading with the aid of a white noise signal and a d.c.\(hycalibrated true r.m.s. level meter. .PP \fINote\fR \ \(em\ The accuracy of measurements related to the zero relative level point (dBm0p or pW0p) also depends on how precisely the relative level at the measuring point (\fIn\fR\d2\uof Figure\ A\(hy1/G.228) is known. .sp 1P .LP B.4.3 \fIInsertion of bandstop filters\fR .sp 9p .RT .PP Only one bandstop filter should be inserted at a time. This limits errors in measurement of intermodulation noise. .RT .sp 1P .LP B.4.4 \fIReadjustment of signal load\fR .sp 9p .RT .PP Normally, the signal load should be readjusted to the nominal value after the insertion of a bandstop filter. When measurements are specifically to investigate second\(hyorder intermodulation, or when this is known to dominate, greater accuracy is obtained by readjusting only for the specified passband insertion loss of the bandstop filter and not for the loss of spectrum energy in the measuring slot. .PP \fINote\fR \ \(em\ The effect of the measuring slot bandwidth is negligible with crystal\(hytype bandstop filters. .RT .sp 2P .LP B.4.5 \fIMeasurement at the receiver\fR .sp 1P .RT .PP B.4.5.1 Using the NPR method the noise power ratio is now measured as the change required in the setting of an attenuator (?63\fIa\fR in Figure\ A\(hy1/G.228) to restore the pointer of the indicating instrument to the original setting. .sp 9p .RT .PP B.4.5.2 Using the direct measuring method the weighted noise level can be read in dBmp (or\ pWp) from the instrument. Optional means may be provided, e.g.\ to shift the calibration by setting a switch to the relative level\ \fIn\fR\d2\uof the measuring access point\ \fIT\fR so that the dBm0p or pW0p values are indicated. .sp 2P .LP B.5 \fICorrections for high accuracy measurements\fR .sp 1P .RT .PP The effects of the following error sources can be reduced by applying corrections to the measured values: .RT .sp 1P .LP B.5.1 \fIReceiver calibration in connection with NPR method\fR .sp 9p .RT .sp 1P .LP B.5.1.1 \fIIrregularity of the noise source\fR .sp 9p .RT .PP The tolerance for the spectrum regularity is \(+- | .5\ dB. A calibration table (or curve) should be available for each noise generator. .bp .RT .sp 1P .LP B.5.1.2 \fIErrors of effective system bandwidth\fR .sp 9p .RT .PP A correction in the conversion of NPR values into noise levels (in\ dBm0p) by application of the correction factor\ k in equation\ (A\(hy2) allows first, for the difference between nominal occupied bandwidth of the system under test and actual bandwidth\ \fIB\fR between bandpass filter effective cut\(hyoff frequencies and secondly, for the difference between nominal occupied bandwidth and the total bandwidth actually occupied by telephone channels (i.e. 4\fIN\fR \ kHz). .RT .sp 1P .LP B.5.1.3 \fIPassband attenuation distortion of bandpass filters at the\fR \fImeasuring frequency\fR .sp 9p .RT .PP The corrections in \(sc\(sc B.5.1.1 and B.5.1.2 should ensure calibration to an accuracy of\ \(+- | .2\ dB. .RT .sp 1P .LP B.5.2 \fIBandstop filter effects\fR .sp 9p .RT .PP If coil\(hycapacitor type bandstop filters are used, it might be worthwhile to assess the error of the measured intermodulation noise due to the effective bandwidth of these filters. To this end the rules quoted in B.2.3.1\ and B.2.3.2\ above should be applied. .PP Approximate corrections for this error are thus possible when the proportion of third\(hy and second\(hyorder intermodulation noise has been determined. .RT .sp 2P .LP B.6 \fILimitations of the noise loading measurement technique\fR .sp 1P .RT .PP B.6.1 Very low noise levels of less than about\ \(em83\ dBm0p (about\ 5\ pW0p) cannot be expected to be measured with an error of less than\ 2\ dB, where the inherent noise leakage of the white noise measuring set is at the limit corresponding to NPR\ \(>="\ 67\ dB as explained in B.2.2\ above. .sp 9p .RT .PP B.6.2 Although the measurements made at the specified frequencies may confirm that the design objectives are met, the noise performance of a system between these frequencies cannot always be inferred accurately from these measurements. Whether this interpolation is justified or not has to be established for the system under consideration. An approximate indication of the frequency dependency can be gained from the frequency characteristic of the basic noise (without loading) which can be measured with the aid of a selective level meter and continuously varying the frequency. The total noise performance of a system may be evaluated, when necessary, by carrying out measurements using additional test equipment. .sp 2P .LP \fBBibliography on accuracy of white noise measuring methods\fR .sp 1P .RT .LP MUELLER\ (M.): Noise loading test errors due to finite slot width, \fIData and Communications design\fR , pp.\ 20\(hy24, March\(hyApril\ 1973. .LP SPINDLER\ (W.): Noise loading measuring procedures and error sources, \fITelecommunications\fR , pp.\ 32C\(hy32F, July\ 1974. .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCIR Recommendation \fIMeasurement of noise using a continuous uniform\fR \fIspectrum signal on frequency\(hydivision multiplex telephony\fR \fIradio\(hyrelay systems\fR , Vol.\ IX, Rec.\ 399, Dubrovnik,\ 1986. .LP [2] CCIR Recommendation \fIMeasurement of performance by means of a signal\fR \fIof a uniform spectrum for systems using frequency\(hydivision multiplex\fR \fItelephony in the fixed\(hysatellite service\fR , Vol.\ IV, Rec.\ 482, Dubrovnik,\ 1986. .LP [3] CCIR Recommendation \fIPre\(hyemphasis characteristic for frequency\fR \fImodulation radio\(hyrelay systems for telephony using frequency\(hydivision\fR \fImultiplex\fR , Vol.\ IX, Rec.\ 275, Dubrovnik,\ 1986. .bp .LP .sp 2P .LP \fBRecommendation\ G.229\fR .RT .sp 2P .sp 1P .ce 1000 \fBUNWANTED\ MODULATION\ AND\ PHASE\ JITTER\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.229'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.229 %' .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1972, further amended)\fR .sp 9p .RT .ce 0 .sp 1P .LP \fB1\fR \fBUnwanted modulation by harmonics of the power supply and other\fR \fBlow frequencies\fR .sp 1P .RT .sp 1P .LP 1.1 \fIRequirements on carrier transmission systems\fR .sp 9p .RT .PP To enable the limit indicated in the Recommendation cited in [1] to be met, it is recommended that a minimum side component attenuation of 45\ dB should be obtained when a signal is transmitted over a channel having the same composition as the 2500\ km hypothetical reference circuit for the system concerned. .PP This limit is subdivided as indicated in \(sc\(sc 1.2 and 1.3 below into allocations to terminal and to line equipment. .RT .LP .sp 1P .LP 1.2 \fICombined effect due to all translating equipment\fR .sp 9p .RT .PP The combined effect due to all translating equipment on the hypothetical reference circuit should correspond to a minimum side component attenuation of 48\ dB. .PP For each translating equipment, send and receive side taken separately, and measured at the signal output, a side component attenuation of at least 63\ dB should be obtained under normal operating conditions. Under adverse power supply conditions a minimum of 60\ dB should be met. It is expected that then an overall value of 48\ dB, indicated above, will only rarely be exceeded. .PP \fINote\fR \ \(em\ The above requirements are derived from the hypothetical reference circuits for the 4\ MHz, 12\ MHz and 60\ MHz systems. The same figures may be applied to other systems provided that their hypothetical reference circuit does not differ significantly from those referred to above. .RT .LP .sp 1P .LP 1.3 \fICombined effects due to all line equipment\fR .sp 9p .RT .PP The combined effects due to all line equipment on the hypothetical reference circuit should correspond to a minimum side component attenuation of 48\ dB. .PP Line equipments can be subject to two types of interference which will cause side components on a transmitted signal: .RT .LP \(em Effects from power supplies (for example, a residual mains frequency ripple may be superimposed on the d.c. power feeding current). These are potentially systematic on the complete length of the circuit. .LP \(em Effects from voltages caused by induction (for example, from railway traction currents). They are not expected to occur as systematically as the effects from the power supplies. .PP The influence caused by \fIpower supply ripple\fR should be such that a minimum side component attenuation of 51\ dB is observed for the combined effect of all line equipment on the hypothetical reference circuit. It is recommended that on a single power feeding section, the side component attenuation should not be less than 51\ +\ 10\ log\ k\ dB, where k is the number of power feeding sections on the hypothetical reference circuit. .PP \fINote\fR \ \(em\ Based on the assumptions that some power feeding sections may be powered from battery supplies and that adverse cumulation over the full length of the hypothetical reference connection is unlikely, it can be expected that the limit of 51\ dB will be observed with a high probability. .PP The influence caused by \fIinduced voltages\fR should be such that a minimum side component attenuation of 51\ dB is observed for the combined effects of all line equipment on the hypothetical reference circuit. However, voltages caused by induction vary considerably with time. The effect of a source of induction is very often confined to one power feeding section. It seems very unlikely that the induced voltage reaches its maximum value in more than one section at the same instant. .PP It is recommended that the r.m.s. value of the longitudinal voltage in a power feeding section caused by induction under normal operating conditions (excluding short circuits and arcing on railways,\ etc.) should not exceed 150\ volts. (This limit has been recommended regarding safety aspects and is contained in\ [2]. It seems reasonable to adopt the same value for the present purpose.) .bp .PP Calculations indicate that an allowance of 6\ dB for the combined effect of several sections under the influence of induction should cover the majority of likely cases. It is therefore recommended that a minimum side component attenuation of 57\ dB should be observed on a power feeding section under the influence of the maximum allowed induced voltage. It is estimated that then the value of 51\ dB on a circuit of 2500\ km would only be exceeded in rare circumstances and infrequently, particularly in view of the fact that only a fraction of the total length would be exposed to interference by induction. .RT .sp 2P .LP \fB2\fR \fBPhase jitter due to translating equipments\fR .sp 1P .RT .PP For each translating equipment, send and receive sides taken separately, a phase jitter on a signal should not exceed 1\(de peak\(hyto\(hypeak when measured on the output of the equipment. The measurement should be of all phase jitter components on each side of the signal in the frequency band 20\(hy300\ Hz, i.e.\ equivalent to the frequency band indicated in Recommendation\ 0.91\ [3]. .PP \fINote\ 1\fR \ \(em\ The above requirement is derived from a consideration of data signals on a telephone\(hytype circuit over a 2500\(hykm hypothetical reference circuit. Conforming to this requirement will ensure a high probability that the overall phase jitter from this source will not exceed 6\(de peak\(hyto\(hypeak. This performance will also ensure a high probability that for telephone speech transmission the phase jitter will be below the detection threshold of a majority of listeners. .PP \fINote\ 2\fR \ \(em\ In practice it is expected that phase jitter of the magnitude given above will occur only on translating equipments using high frequency carriers and that correspondingly lower phase jitter will be caused by translating equipment using lower frequency carriers. .PP \fINote\ 3\fR \ \(em\ Where the phase jitter is caused mainly by random noise a peak\(hyto\(hypeak/r.m.s. ratio of\ 10 should be assumed. .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fIGeneral performance objectives applicable to all\fR \fImodern international circuits and national extension circuits\fR , Vol.\ III, Rec.\ G.151, \(sc\ 7. .LP [2] CCITT manual \fIDirectives concerning the protection of telecommunication\fR \fIlines against harmful effects from electricity lines\fR , Chapter\ IV, \(sc\(sc\ 6, 7 and\ 71, ITU, Geneva,\ 1963, 1965, 1974,\ 1978. .LP [3] CCITT Recommendation \fIEssential clauses for an instrument to measure\fR \fIphase jitter on telephone circuits\fR , Vol.\ IV, Rec.\ O.91. \v'1P' .IP \fB2.3\fR \ \fBTranslating equipment used on various carrier\(hytransmission\fR \fBsystems\fR \v'6p' .sp 1P .RT .sp 2P .LP \fBRecommendation\ G.230\fR .RT .sp 2P .ce 1000 \fBMEASURING\ METHODS\ FOR\ \fR \fBNOISE\ PRODUCED\ BY\ MODULATING\ EQUIPMENT\fR .EF '% Fascicle\ III.2\ \(em\ Rec.\ G.230'' .OF '''Fascicle\ III.2\ \(em\ Rec.\ G.230 %' .ce 0 .sp 1P .ce 1000 \fBAND\ THROUGH\(hyCONNECTION\ FILTERS\fR .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1976 and 1980)\fR .sp 9p .RT .ce 0 .sp 1P .PP Considering the provisions of Recommendation\ G.222, \(sc\ 4 and the assumptions for the calculation of noise of Recommendation\ G.223, the following methods for measuring the noise produced by modulating equipments are recommended: .sp 1P .RT .sp 2P .LP \fB1\fR \fB12\(hychannel translating equipments\fR .sp 1P .RT .PP For the measurement of noise produced by 12\(hychannel translating equipments, eleven incoherent noise random signals with a normal (Gaussian) .bp .PP level distribution and with a power distribution according to Recommendation\ G.227 should be used. As a provisional value, the peak/r.m.s. ratio of each of the noise signals should be about 12\ dB. The allocation on the 12\(hychannel inputs of the conventional load of 2140\ \(*mW0 (+3.3\ dBm0) should be as follows: .RT .ad r 1 channel being measured \ \ \ 0\ \(*mW0 .ad b .RT .ad r 2 adjacent channels at 32 \(*mW0 (\(em15 dBm0) each \ \ 64\ \(*mW0 .ad b .RT .ad r 9 channels at 230 \(*mW0 (\(em6.4 dBm0) each 2070 \(*mW0 .ad b .RT .ad r 2134\ \(*mW0 .ad b .RT .LP .sp 2P .LP \fB2\fR \fBHigher order translating equipments\fR .sp 1P .RT .sp 1P .LP 2.1 \fIAllocation of loading\fR .sp 9p .RT .PP For the measurement of noise produced by higher order translating equipments (groups, supergroups, etc. translating equipment), the values for the allocation of the conventional load to the different translating equipments are given in Table\ 1/G.222. .PP The number of incoherent band\(hylimited white noise signals is assumed to be equal to the number of the input ports of the groups, supergroups, etc. translating equipment under measurement. In certain circumstances, however, the number of noise signals may be smaller than the number of group input ports. .RT .sp 1P .LP 2.2 \fIMeasuring frequencies\fR .sp 9p .RT .PP The measuring frequencies in Table\ 1/G.230 are recommended. .RT .LP .rs .sp 15P .ad r \fBtable 1/G.230 (maintenu) T1.230, p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP 2.3 \fIFilter characteristics\fR .sp 9p .RT .PP The following filter characteristics are recommended: .RT .PP 2.3.1 bandpass filters (see Table 2/G.230); .PP 2.3.2 bandstop filters (see Table 3/G.230). .PP \fINote\fR \ \(em\ Measuring frequencies of Table\ 1/G.230 and filter characteristics of Tables\ 2/G.230 and 3/G.230 (with the exception of the 70\(hykHz filter) are the same as in CCIR Recommendations\ 399\ [1] and 482\ [2] and CCITT Recommendation\ G.228 used for line system arrangements. Annex\ B to Recommendation\ G.228 deals with the subject of corrections, if any, to be applied to measurements to allow for filter effects. .bp .LP .rs .sp 22P .ad r \fBtable 2/G.230 (maintenu) T2.230, p.\fR .sp 1P .RT .ad b .RT .ce \fBH.T. [T3.230]\fR .ce TABLE\ 3/G.230 .ce \fBBandstop filters\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(36p) | cw(30p) sw(36p) sw(30p) | cw(36p) sw(30p) | cw(30p) , ^ | c | c | c | c | c | ^ . { Centre frequqency \fIf\fI (kHz) } { Bandwith (kHz) in relation to \fIf\fI over which the discrimination should be at least } { Bandwith (kHz), in relation to \fIf\fI outside of which the discrimination should not exceed } Notes 70 dB 55 dB 30 dB 3 dB 0.5 dB _ .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | lw(30p) . \ \ | 70 \(+-1.5 \(+-\ 1.7 \(+-\ 2.0 \(+-\ \ 5 \(+-\ 10 .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ \ | 98 \(+-1.5 \(+-\ 1.8 \(+-\ 2.1 \(+-\ \ 4 \(+-\ \ 9 a) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ \ | 31 \(+-1.5 \(+-\ 2.7 \(+-\ 4.0 \(+-\ 17 \(+-\ 30 .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ \ | 34 \(+-1.5 \(+-\ 3.5 \(+-\ 7.0 \(+-\ 15 \(+-\ 48 b) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 1 | 02 \(+-1.5 \(+-\ 4.0 \(+-\ 9.0 \(+-\ 27 \(+-\ 90 a) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 1 | 48 \(+-1.5 \(+-\ 4.0 \(+-11.0 \(+-\ 35 \(+-110 b) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 1 | 30 \(+-1.5 \(+-\ 4.2 \(+-14.0 \(+-\ 48 \(+-155 a) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 3 | 86 \(+-1.5 \(+-\ 1.8 \(+-\ 3.5 \(+-\ 12 \(+-100 b) .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 3 | 86 \(em \(+-15.0 \(+-30.0 \(+-110 \(+-350 .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . \ 9 | 73 \(+-1.5 \(+-\ 2.7 \(+-\ 5.8 \(+-\ 18 \(+-250 .T& cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) . 11 | 00 \(+-1.5 \(+-\ 3.0 \(+-\ 7.0 \(+-\ 20 \(+-300 b) .TE .LP a) CCIR Recommendation 482 [2]. .LP b) CCIR Recommendation 399 [1]. .TE .nr PS 9 .RT .ad r \fBtable 3/G.230 [T3.230], p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP 2.4 \fIMeasuring procedures\fR .sp 9p .RT .PP The measuring procedures should comply with Recommendation\ G.228. Measurements must be carried out with the regulators, if any, not included and with the levels at the nominal value. .PP \fINote\fR \ \(em\ Some Administrations have chosen for groups and supergroups not being tested in conformance with Table\ 1/G.230 higher values of the load, but only for testing equipments with some margin to take account of the application where higher than nominal activity is to be expected. .PP As a consequence, in such cases, higher noise limits have to be admitted than those indicated in Recommendation\ G.222, \(sc\ 4). .bp .RT .sp 2P .LP \fB3\fR \fBThrough\(hyconnection filters\fR .sp 1P .RT .sp 1P .LP 3.1 \fIAllocation of loading\fR .sp 9p .RT .PP For the measurement of noise produced by through\(hyconnection filters the values for the allocation of the conventional load according to Table\ 2/G.223 to the different filters are given in Table\ 4/G.230. .RT .ce \fBH.T. [T4.230]\fR .ce TABLE\ 4/G.230 .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(60p) | cw(60p) | cw(60p) . Filter for the basic { Band of the noise spectrum (kHz) } { Level of the noise power (dBm0) } _ .T& lw(60p) | cw(60p) | cw(60p) . Group { \ | 12 to \ \ | 52 \ | 60 to \ \ | 08 } { + \ 6.1 (=^ \ | 60 channels) + \ 3.3 (=^ \ | 12 channels) } .T& lw(60p) | cw(60p) | cw(60p) . Supergroup { \ | 60 to \ 1 | 96 \ | 16 to \ \ | 52 } { + \ 9.8 (=^ \ | 00 channels) + \ 6.1 (=^ \ | 60 channels) } .T& lw(60p) | cw(60p) | cw(60p) . Mastergroup \ | 16 to \ 2 | 00 { + 12.3 (=^ \ | 30 channels) } .T& lw(60p) | cw(60p) | cw(60p) . Supermastergroup 4 | 70 to 17 | 00 + 17.6 (=^ 1800 channels) .T& lw(60p) | cw(60p) | cw(60p) . 15 supergroup assembly \ | 16 to \ 8 | 60 + 17.6 (=^ 1800 channels) .TE .LP \fINote\ 1\ \fR \(em\ Group and supergroup through\(hyconnection filters require two measurements. One with \*Qbroadband loading\*U with components outside the pass\(hyband, and an additional one with loading in the passband only. Since in these cases the number of transmitted channels is smaller than 240 (the range where the power level of the conventional load is not proportional to 10\ log 1 0 | fIn\fR , see \(sc\ 2.1 of Recommendation\ G.223) the proportional part of the broadband loading transmitted in the passband gives a loading which is lower than the conventional load for 12 or 60\ channels respectively. .LP \fINote\ 2\ \fR \(em\ The choice of the correct load figure for the measurement of the noise produced by the through\(hysupermastergroup filter requires careful consideration bearing in mind that band limiting filters for a bandwidth complying with actual load conditions are not available. .nr PS 9 .RT .ad r \fBTable 4/G.230 [T4.230], p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP 3.2 \fIMeasuring frequencies\fR .sp 9p .RT .PP See \(sc\ 2.2. .RT .sp 1P .LP 3.3 \fIFilter characteristics\fR .sp 9p .RT .PP Highpass and lowpass filters complying with Table\ 2/G.228 and\ [3] can be used to limit the frequency of the noise spectrum. For bandstop filters, see Table\ 3/G.230. .RT .sp 1P .LP 3.4 \fIMeasuring procedures\fR .sp 9p .RT .PP The measuring procedure should comply with Recommendation\ G.228. For through\(hygroup and through\(hysupergroup filters, two measurements have to be carried out in the appropriate measuring slots in the passband. .RT .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCIR Recommendation \fIMeasurement of noise using a continuous uniform\fR \fIspectrum signal on frequency\(hydivision multiplex telephony\fR \fIradio\(hyrelay systems\fR , Vol.\ IX, Rec.\ 399, Dubrovnik,\ 1986. .LP [2] CCIR Recommendation \fIMeasurement of performance by means of a signal of\fR \fIa uniform spectrum for systems using frequency\(hydivision multiplex\fR \fItelephony in the fixed satellite service\fR , Vol.\ IV, Rec.\ 482, Dubrovnik,\ 1986. .LP [3] CCIR Recommendation \fIMeasurement of performance by means of a signal\fR \fIof a uniform spectrum for systems using frequency\(hydivision multiplex\fR \fItelephony in the fixed satellite service\fR , Vol.\ IV, Rec.\ 482, Table\ I, Dubrovnik,\ 1986. .LP .bp