.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 Q.1 and Q.2\fR \v'2P' .EF '% \ \ \ ^'' .OF ''' \ \ \ ^ %' .ce 0 .sp 1P .ce 1000 \fBSIGNALLING\ IN\ THE\ INTERNATIONAL\ MANUAL\ SERVICE\fR .ce 0 .sp 1P .LP .rs .sp 30P .ad r Blanc .EF '% \ \ \ ^'' .OF ''' \ \ \ ^ %' .ad b .RT .LP .bp .LP \fBMONTAGE:\fR \ PAGE 2 = PAGE BLANCHE .sp 1P .RT .LP .bp .sp 2P .LP \fBRecommendation\ Q.1\fR .RT .sp 2P .sp 1P .ce 1000 \fBSIGNAL\ RECEIVERS\ FOR\ MANUAL\ WORKING\fR \v'6p' .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.1'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.1 %' .ce 0 .sp 1P .PP In 1934 (CCIF \fIWhite Book\fR , Volume\ III, Xth\ Plenary Assembly, Budapest,\ 1934), a signalling current having a frequency of 500\ Hz\ \(+-\ 2%, interrupted at a frequency of 20\ Hz\ \(+-\ 2% was provisionally chosen for manually\(hyoperated international circuits. .sp 1P .RT .PP 500\ Hz was chosen as the frequency to be transmitted, under normal conditions, by carrier terminal equipment and line repeaters. To avoid false operation due to speech currents, it was also considered desirable to interrupt the 500\ Hz signalling current at low frequency. The use of a uniform interruption frequency of 20\ Hz enables a high degree of selectivity to be obtained in signal receivers. .PP The effective power produced by the signalling current, when not interrupted, is fixed at 1\ milliwatt at a zero relative level or an absolute power level of zero (with a tolerance of \(+- | \ decibel) which corresponds to an average power for the interrupted signalling current of 0.5\ milliwatt, with a tolerance of \(+- | \ decibel. .PP The power levels specified above were chosen in\ 1954 (XVIIth\ CCIF Plenary Assembly, Geneva,\ 1954) on the basis of the limit imposed for the maximum energy which can be transmitted by signals during the busy hour; it must not exceed 2.5\ microwatthours or 9000\ microwattseconds at a zero relative level point. A reasonable value for the number of calls, or attempted calls, on a circuit during the busy hour was assumed and 2\ seconds was assumed to be the sending duration of the signalling current to line by operation of the operator's ringing key. .PP On outgoing circuits from an international exchange, where the 500/20\ Hz signals are liable to be sent over wideband carrier systems (coaxial carrier systems) it is desirable, to avoid overloading the repeaters, that the duration of the 500/20\ Hz signals sent to line should not exceed 2\ seconds and they should be limited to this value by automatic means. .PP Since, in general, the \fIInstructions for the International Telephone\fR \fIService\fR | Article\ 32)\ [1] require the signalling current sent over an international circuit to have a duration of at least 2\ seconds to avoid the risk of signals being undetected at the incoming end, the means for limiting the sending duration of the signalling current will generally consist of an arrangement which controls the sending duration independently of the time the ringing key is operated and which automatically fixes that duration at\ 2\ seconds. .PP \fINote\fR \ \(em\ In the case of short 2\(hywire circuits, it may be economical to use, by agreement between the Administrations concerned, a low\(hyfrequency signalling current (either between\ 16 and\ 25\ Hz or\ 50\ Hz). \v'1P' .RT .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation Q.1) .sp 9p .RT .ce 0 .ce 1000 \fBBasic technical clauses of a model specification for the provision\fR .sp 1P .RT .ce 0 .ce 1000 \fBof 500/20\(hyHz voice\(hyfrequency signalling sets\fR .ce 0 .ce 1000 \fB(signal transmitters and receivers) intended\fR .ce 0 .ce 1000 \fBfor manually\(hyoperated circuits\fR .ce 0 .LP A.1 \fISending of signals\fR .sp 1P .RT .PP \fIPower\fR \ \(em\ The signal transmitted shall supply a sinusoidal current at a frequency of 500\ Hz\ \(+-\ 2% interrupted at a frequency of\ 20\ Hz\ \(+-\ 2%. .PP The effective mean power of the 500/20\(hyHz current is fixed at 0.5\ milliwatt or an absolute power level of \(em3\ dBm (with a tolerance of \(+- | \ dB) at a zero relative level point. .PP Every precaution should be taken to avoid unbalance effects in the circuit during the transmission of a 500/20\(hyHz signalling current. .bp .RT .sp 1P .LP A.2 \fIReception of signals\fR .sp 9p .RT .PP \fISensitivity\fR \ \(em\ The signal receiver shall operate correctly when the 500/20\(hyHz current at the input to the signal receiver is within the following limits: .RT .sp 1P .ce 1000 \(em8.5\ +\ \fIn\fR \ \(=\ \fIN\fR \ \(=\ +2.5\ +\ \fIn\fR \ dB .ce 0 .sp 1P .LP where \fIn\fR \ is the relative power level at the point of the circuit at which the signal receiver is connected. .PP The limits take account of the tolerances indicated above for the transmitted power level and include a margin of \(+- | .5\ decibels on the nominal absolute power level of the 500/20\ Hz current received at the input to the signal receiver. This margin allows for variations in transmission conditions on international circuits. .PP \fITuning\fR \ \(em\ Tuning should be such that the signal receiver operates only at a frequency of 500\ Hz guaranteed to within \(+- | % and at an interrupting frequency of 20\ Hz guaranteed to within\ \(+- | %. .PP \fIDelay\fR \ \(em\ The delay, i.e. the time which elapses between the application of the signalling voltage and the operation of the signal receiver, must be long enough for the signal receiver to remain insensitive to all speech currents which normally flow in the circuit to which it is connected. The duration of this delay must, however, be less than 1200\ milliseconds. (In other words, 1200\ milliseconds is the maximum signal recognition time within which a signal has to be recognized.) .PP \fISelectivity\fR (resulting from the tuning of the resonant circuit and the delay mentioned above)\ \(em\ The receipt of a speech (or noise) current circulating in the circuit must not give rise to a current liable to cause the operation of the signalling equipment and, in consequence, to cause a wrong indication to be given on the international positions even though the speech (or noise) voltage reaches the maximum value likely to be met in practice. In particular, the signal receiver must not operate when a speech power not exceeding 6\ milliwatts is applied at a zero relative level point. .PP \fIInsertion loss\fR \ \(em\ The insertion loss introduced by the signal receiver in the circuit with which the signalling set is associated must be less than 0.3\ dB for any frequency effectively transmitted by the circuit. .RT .sp 2P .LP \fBReference\fR .sp 1P .RT .LP [1] CCITT \fIInstructions for the international telephone service\fR \fI(1\ October\ 1985)\fR , ITU, Geneva,\ 1985. \v'1P' .sp 2P .LP \fBRecommendation\ Q.2\fR .RT .sp 2P .ce 1000 \fBSIGNAL\ RECEIVERS\ FOR\ AUTOMATIC\ AND\ SEMI\(hyAUTOMATIC\ WORKING,\fR .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.2'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.2 %' .ce 0 .sp 1P .ce 1000 \fBUSED\ FOR\ MANUAL\ WORKING\fR .ce 0 .sp 1P .PP The directives relating to 500/20\(hyHz signalling sets are provisional. An Administration intending to purchase new signalling sets for use on international circuits which for the time being are to be operated on a manual basis, may find it advantageous, by agreement with the Administrations interested in the operation of the circuits concerned, to use signal receivers and transmitters conforming to the specifications for international automatic equipment. This will permit a greater technical uniformity of installations and will avoid having to replace the signal receivers when, ultimately, these circuits are operated on an automatic or semi\(hyautomatic basis. .sp 1P .RT .PP The signal receivers must therefore conform with the specifications for the applicable recommended CCITT systems. .LP .sp 1P .LP \fISending of signals\fR .sp 9p .RT .PP The frequency and power level of the signalling current must be in accordance with the specifications for international automatic equipment. If two\(hyfrequency signal receivers are concerned, the two frequencies (compound signal) must be transmitted simultaneously. .PP The nominal duration of a signal sent to line is fixed at 2\ seconds so as to be the same as that specified for 500/20\ Hz signalling. .bp .RT .sp 1P .LP \fIReception of signals\fR .sp 9p .RT .PP At the receiving end, provision must be made for a splitting arrangement conforming to the specifications for international automatic equipment. This splitting arrangement can be: .RT .LP \(em either an integral part of the signal receivers, or .LP \(em placed at the end of the circuit after the signal receiver. .PP The signalling equipment (at the output of the signal receiver) which causes the lighting of the calling and clearing lamps shall have a signal recognition time of between\ 100 and\ 1200\ milliseconds: .LP \(em the minimum duration of 100\ ms has been chosen so as to avoid the recognition of false signals due to imitation by speech currents; .LP \(em the maximum duration of 1200\ ms has been chosen so as to permit the partial use of 500/20\(hyHz signal\(hyreceiver equipment. .PP \fINote\ 1\fR \ \(em\ The characteristics of signal receivers of the types used for automatic or semi\(hyautomatic working could possibly also be used to provide signals and supplementary facilities for operators if the Administrations concerned consider that the operational advantages to be obtained justify the equipment modifications involved at the international exchanges. .PP \fINote\ 2\fR \ \(em\ The time quoted in this Recommendation for the signal length and the signal recognition times would also be appropriate for out\(hyband signalling systems using discontinuous signals for a manual service. .RT .LP .rs .sp 31P .LP .bp .LP \fBMONTAGE:\fR PAGE 6 = PAGE BLANCHE .sp 1P .RT .LP .bp .sp 1P .ce 1000 \v'12P' \s12PART\ II \v'4P' .RT .ce 0 .sp 1P .ce 1000 \fBRecommendations Q.4 to Q.49\fR \v'2P' .EF '% \ \ \ ^'' .OF ''' \ \ \ ^ %' .ce 0 .sp 1P .ce 1000 \fBGENERAL\ RECOMMENDATIONS\ RELATING\fR .ce 0 .ce 1000 \fBTO\ \fR \fBSIGNALLING\ AND\ SWITCHING\fR .ce 0 .sp 1P .ce 1000 \fBIN\ THE\ AUTOMATIC\ AND\ SEMI\(hyAUTOMATIC\ SERVICES\fR .ce 0 .sp 1P .LP .rs .sp 28P .ad r Blanc .EF '% \ \ \ ^'' .OF ''' \ \ \ ^ %' .ad b .RT .LP .bp .LP \fBMONTAGE:\fR \ PAGE 8 = PAGE BLANCHE .sp 1P .RT .LP .bp .sp 1P .ce 1000 \v'3P' SECTION\ 1 .ce 0 .sp 1P .ce 1000 \fBCCITT\ BASIC\ RECOMMENDATIONS\ ON\ INTERNATIONAL\fR .ce 0 .sp 1P .ce 1000 \fBAUTOMATIC\ AND\ SEMI\(hyAUTOMATIC\ WORKING\fR .ce 0 .sp 1P .sp 2P .LP \fBRecommendation\ Q.4\fR .RT .sp 2P .sp 1P .ce 1000 \fBAUTOMATIC\ SWITCHING\ FUNCTIONS\ FOR\ USE\fR | \fBIN\ NATIONAL\ NETWORKS\fR \v'1P' .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.4'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.4 %' .ce 0 .sp 1P .LP \fB1\fR \fBPreamble\fR .sp 1P .RT .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (1) that a large amount of switching equipment will be installed in the next few years, especially in areas of low subscriber density; .LP .PP (2) the continuous rapid development of new switching techniques results in different generations of equipment having to co\(hyexist; .PP (3) that some degree of compatibility in the installed switching equipment is required in the world\(hywide automatic network; .PP (4) that the introduction of newly developed switching systems presents Administrations with an ever increasing number of engineering, staff training, maintenance and other operational considerations, .sp 1P .LP \fIand also considering\fR .sp 9p .RT .PP (5) that Recommendations originally intended for international application only are increasingly being applied to national networks, or could be so applied; .PP (6) that many current studies are aimed at producing Recommendations primarily applicable to national networks, .sp 1P .LP \fIrecommends\fR .sp 9p .RT .PP the following guidelines for use by Administrations establishing national switching standards or, if desired, for updating existing standards. Each Administration may select those guidelines it deems applicable to its own situation. .sp 2P .LP \fB2\fR \fBAutomatic switching functions for use in national networks\fR .sp 1P .RT .PP Table 1/Q.4 lists the functional switching capabilities of an exchange which will, or may in some instances, according to the role of the exchange in a network, need to be technically specified in order that the Administration concerned can be assured that the exchange will satisfy existing and foreseen future needs of the network. For the required capabilities, references are given to CCITT\ texts which should be taken into account when decisions on national standards are taken; some make positive recommendations, others give guidelines or background information. Table\ 2/Q.4 provides full titles for those referenced texts, and for others applicable to national switching, in order to provide more specific information about the subject matter. .bp .PP Some of the functions listed are required in all types of exchanges. Others may or may not be, according to the role of the exchange, e.g.\ local, combined local/transit, transit, international,\ etc. .PP It is not always necessary that a precise technical specification be given, e.g.,\ in a tender specification, for each switching function. In some instances, it may be sufficient to state the requirements broadly, possibly including desired ranges of parameter values, and to invite a tenderer to make his own specific proposals for evaluation. .RT .sp 2P .LP \fB3\fR \fBRequirements for ISDN\fR .sp 1P .RT .PP As Recommendations for the ISDN are being developed concurrently, it is difficult to reference them in this Recommendation. All Recommendations relevant to the ISDN will be published in a single volume at the end of this Study Period\ 1981\(hy1984 (Fascicle\ III.5). .RT .sp 2P .LP \fB4\fR \fBRequirements other than automatic switching functions\fR .sp 1P .RT .LP .PP The technical specifications of the required automatic switching functions of an exchange do not, in themselves, consitute a complete specification. Other aspects possibly needing to be covered, which are particular to an exchange or to a group of exchanges and not included within the scope of automatic switching functions are: .RT .LP \(em traffic (dimensioning and service performance); .LP \(em specifications dictated by the equipment environment (building constraints, power supplies, climatic conditions,\ etc.); .LP \(em installation, including testing, acceptance, post\(hyacceptance technical support,\ etc.; .LP \(em training and documentation; .LP \(em support of system design and software, e.g., CCITT Recommendation\ Z.100 (SDL) series and CCITT Recommendation\ Z.200 (CHILL) series. .LP .sp 2P .LP \fB5\fR \fBTechnical cooperation possibilities\fR .sp 1P .RT .PP The CCITT Recommendations already established so far do not themselves suffice to cover all the points of a specification dealing with the functions to be performed by switching equipment. It is unavoidable, if national standards are to match the requirements and circumstances of a particular network, that the responsible Administration itself exercise a number of choices. .PP An Administration seeking advice or guidance beyond that indicated in CCITT\ texts may, by approaching the ITU\ Secretariat, obtain information on the standards adopted by other Administrations. .RT .sp 2P .LP \fB6\fR \fBDefinition of requirements in terms of services and facilities\fR .sp 1P .RT .PP 6.1 Fundamental decisions as to range of service(s) and facilities to be provided must be made by the Administration. Descriptions and other information on the various services normally provided by a switching system may be found as indicated in the following: .sp 9p .RT .LP \(em types of services (GAS 6, Chapter\ II, \(sc\ 3; Chapter\ III, \(sc\ 3.2), .LP \(em basic services (GAS 6, Chapter\ IV, \(sc\ 1.2), .LP \(em supplementary services (GAS 6, Chapter\ IV, \(sc\ 1.4); Recommendations\ E.130, E.132, E.151; Supplement No.\ 1 to Series\ E Recommendations. .PP 6.2 A list of possible telephony subscriber services and facilities has been extracted from the GAS\ 6 Handbook, Chapter\ IX, \(sc\ 1.3.2 and is shown in Annex\ A. .LP .rs .sp 5P .ad r \fBBlanc\fR .ad b .RT .LP .bp .ce \fBH.T. [1T1.4]\fR .ce TABLE\ 1/Q.4 .ce \fBCCITT texts (Recommendations and GAS Handbooks) relevant to the\fR .ce .ce \fBtechnical specification of automatic .ce \fBswitching functions of exchanges\fR .ce .ce \fBin national networks\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(138p) | cw(90p) . Item Reference _ .T& lw(138p) | cw(90p) . A. \fISwitching\fR .T& lw(138p) | lw(90p) . { \fIType of switch:\fR | analogue (2\(hy or 4\(hywire)/digital, space or time division } { GAS 6 II 1, VI 1.1 GAS 3 III, Annex 1 Recs. Q.501, Q.511 } .T& lw(138p) | lw(90p) . { \fIType of control:\fR | distributed/centralized } GAS 6 VI 1.2 .T& lw(138p) | lw(90p) . { \fISubscriber classification\fR } GAS 6 VI 1.2.1 .T& lw(138p) | lw(90p) . { B. \fIRouting and selection\fR } .T& lw(138p) | lw(90p) . { \fIClassification of exchange inlets and outlets:\fR | according to types of inter\(hyexchange circuits to be connected: taking into account the line, inter\(hyregister,\ etc., signalling arrangements and the transmission, operating, testing, network management,\ etc., requirements } { GAS 6 IV 5.6\(hy7 VI 1.4.1 and 4 Recs. E.543 Q.7, Q.48, Q.49, Q.108, Q.110, Q.251\(hyQ.300, Q.310\(hyQ.331, Q.400\(hyQ.480, Q.501\(hyQ.507, Q.511\(hyQ.517 } .T& lw(138p) | lw(90p) . { \fINumber analysis functions:\fR | required capacity and depth of analysis for routing, determination of number length, barring, digit insertion/deletion, charging, echo control,\ etc. } { GAS 6 IV 6, VI 1.4.6 Recs. E.160, E.161, E.163 Q.103, Q.105, Q.106, Q.107, Q.107 | fIbis\fR , Q.115 } .T& lw(138p) | lw(90p) . { \fIChoice of outgoing circuit:\fR search procedure, dual seizures, alternative routing, repeat attempts,\ etc. } { GAS 6 VI 1.4.2, 3 and 5 Recs. E.170, E.171 Q.12\fR , Q.263 } .T& lw(138p) | lw(90p) . { \fINetwork management functions:\fR | circuit group denial, alternative routing cancellation, exchange load control,\ etc. } { GAS 6 VI 1.4.7 Recs. E.170, E.410, E.411, E.412, E.413 Q.506, Q.516 } .T& lw(138p) | lw(90p) . C. \fICharging\fR .T& lw(138p) | lw(90p) . { \fIMethods:\fR | local, long\(hydistance, international, non\(hychargeable, payphone,\ etc., calls } { GAS 6 IV 7.1\(hy2, VI 1.5.1 Recs. E.230\(hyE.232 } .T& lw(138p) | lw(90p) . { \fICharge determination:\fR | principles and parameters \fR } GAS 6 IV 7.3, VI 1.5.2 .T& lw(138p) | lw(90p) . { D. \fITransmission characteristics\fR } .T& lw(138p) | lw(90p) . { \fIInterfaces:\fR | specification of the transmission characteristics of the interfaces, or the identification of the standard interfaces, at which the exchange is to interconnect with external facilities and systems } { GAS 3 III Recs. G.703, G.704, G.705, G.731\(hyG.739, G.741\(hyG.746, Q.502, Q.512 } .T& lw(138p) | lw(90p) . { \fIExchange transmission performance:\fR | Limits for the levels of transmission impairments attributable to the exchange and for characteristics affecting performance, taking account of all possible types of connection through the exchange \fR } { GAS 6 VI 1.8 Recs. G.121, G.122, G.123 Q.45, Q.507, Q.517 } .T& lw(138p) | lw(90p) . { E. \fISynchronization and timing\fR } { Recs. G.811, G.822 Q.502, Q.503, Q.512, Q.513 } .T& lw(138p) | lw(90p) . { F. \fITones and recorded announcements\fR } .T& lw(138p) | lw(90p) . { Scope and applications; tones; announcements } { GAS 6 VI 1.7 Recs. E.180 (Q.35), E.181 (Q.36), E.182 Supplement No. 2 to Series E Recommendations Rec. Q.24 } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU 1/Q.4 [1T1.4], p. 1\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fR .ce \fBH.T. [2T1.4]\fR .ce TABLE\ 1/Q.4 \fI(cont.)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(138p) | cw(90p) . Item Reference _ .T& lw(138p) | cw(90p) . { G. \fISubscriber line characteristics\fR } .T& lw(138p) | cw(90p) . { 1. \fIAnalogue subscriber line\fR } .T& lw(138p) | lw(90p) . { \fISubscriber line standards:\fR limits for loop resistance, loop insulation, overall line attenuation,\ etc. } { GAS 2 V 3.2, 3.3 GAS 6 VI 1.3.1 GAS 3 II 3.1 Recs. G.120\(hyG.123 } .T& lw(138p) | lw(90p) . { \fISubscriber line signals:\fR supervision address information, ringing, metering, tones,\ etc. } { GAS 2 V 6.2 GAS 6 IV 8, VI 1.3.2 Recs. E.131 Q.16, Q.23, Q.35 (E.180), Q.118 } .T& lw(138p) | lw(90p) . { 2. \fIDigital subscriber line\fR } .T& lw(138p) | lw(90p) . { Exchange interfaces signalling for digital access } { Recs. I.412 Q.512, Q.920, Q.921, Q.930, Q.931 } .T& lw(138p) | lw(90p) . { H. \fIInter\(hyexchange signalling\fR } .T& lw(138p) | lw(90p) . { Specification of required exchange functions by identification of existing and planned inter\(hyexchange signalling arrangements } .T& lw(138p) | lw(90p) . { \fISignalling philosophies and types of signalling\fR \fR } { GAS 6 II 2, IV 8, VI 1.6 GAS 3 II 3.2 Recs. Q.7, Q.21 Supplement No. 3 to Series Q Recommendations } .T& lw(138p) | lw(90p) . { \fISignalling system specifications\fR | channel associated and common channel, as appropriate) \fR } { Recs. Q.101\(hyQ.103, Q.105\(hyQ.118 | fIbis\fR , Q.251\(hyQ.300, Q.310\(hyQ.331, Q.400\(hyQ.490, Q.701\(hyQ.795 } .T& lw(138p) | lw(90p) . { \fIInterworking of signalling systems\fR } Recs. Q.601\(hyQ.685 .T& lw(138p) | lw(90p) . I. \fIOperation\fR .T& lw(138p) | lw(90p) . { The specification of exchange features designed to facilitate the operation of the exchange with respect to the administrations of: \(em\ subscribers \(em\ routing \(em\ traffic \(em\ tariffs and charging \(em\ recording and billing \(em\ system control taking into account remote control possibilities } { GAS 6 IV 7.4\(hy7, 9.1\(hy2 VI 1.5.3\(hy4, 1.9 Recs. E.500 Q.505, Q.506, Q.515, Q.516 Z.331\(hyZ.333 } .T& lw(138p) | lw(90p) . J. \fIMaintenance\fR .T& lw(138p) | lw(90p) . { The specification, with respect to maintenance, of: \(em\ subscriber lines \(em\ inter\(hyexchange circuits \(em\ switching network \(em\ control system the specification of testing and maintenance features, taking into account the objectives of: \(em minimization of the fault rate .line \(em simplification of maintenance activities .line \(em adequate equipment repair facilities .line \(em maximization of immunity to failures .line \(em optimizing maintenance centralization } { GAS 6 IV 9.1, 9.3, VI 1.10 Recs. G.231 M.565 O.22 (Q.49) Q.506, Q.516 Z.301, Z.331\(hyZ.333 } .T& lw(138p) | lw(90p) . { L. \fIInput/output devices for operation and\fR \fImaintenance\fR } { GAS 6 VI 1.11 Recs. E.220, E.221 Z.301\(hyZ.302, Z.311\(hyZ.317, Z.321\(hyZ.323 } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU 1/Q.4 [2T1.4], p. 2\fR .sp 1P .RT .ad b .RT .LP .bp .ce 1000 TABLE\ 2/Q.4 .sp 1P .RT .ce 0 .ce 1000 \fBTitles of CCITT texts (Recommendations and GAS Handbooks)\fR .ce 0 .ce 1000 \fBrelevant to national switching applications\fR .ce 0 .LP CCITT Manual \fILocal telephone networks\fR , ITU, Geneva, 1968 (Gas 2 Handbook). .LP CCITT Manual \fITransmission planning of switched telephone networks\fR , ITU, Geneva,\ 1976 (Gas 3 Handbook). .LP CCITT Manual \fIEconomic and technical aspects of the choice of telephone\fR \fIswitching systems\fR , ITU, Geneva, 1981 (GAS\ 6 Handbook). .LP CCITT Manual \fIEconomic and technical aspects of the transition from\fR \fIanalogue to digital telecommunication networks\fR , ITU, Geneva, 1984 (GAS\ 9 Handbook). .LP CCITT Rec. E.130 \fIChoice of the most useful and desirable supplementary\fR \fItelephone services\fR . .LP CCITT Rec. E.131 \fISubscriber control procedures for supplementary\fR \fIservices\fR . .LP CCITT Rec. E.132 \fIStandardization of elements of control procedures\fR \fIfor supplementary telephone services\fR . .LP CCITT Rec. E.151 \fIConference calls\fR . .LP CCITT Rec. E.160 \fIDefinitions relating to national and international\fR \fInumbering plans\fR . .LP CCITT Rec. E.161 \fIArrangement of figures, letters and symbols on\fR \fIrotary dials and pushbutton telephone sets\fR . .LP CCITT Rec. E.163 \fINumbering plan for the international telephone\fR \fIservice\fR . .LP CCITT Rec. E.170 \fIOverflow \(em alternative routing \(em rerouting \(em\fR \fIautomatic repeat attempt\fR . .LP CCITT Rec. E.171 \fIInternational routing plan\fR . .LP CCITT Rec. E.180 \fICharacteristics of the dial tone, ringing tone,\fR \fIbusy tone, congestion tone, special information tone and warning tone\fR . .LP CCITT Rec. E.181 \fICustomer recognition of foreign tones\fR . .LP CCITT Rec. E.182 \fIApplication of tones and recorded announcements\fR \fIin telephone services\fR . .LP CCITT Rec. E.211 \fINumbering and dialling procedures for VHF/UHF and\fR \fImaritime mobile satellite services\fR . .LP CCITT Rec. E.220 \fIErgonomic aspects of visual display terminals\fR . .LP CCITT Rec. E.221 \fIHuman interface to visual display terminals\fR . .LP CCITT Recs. E.230\(hyE.232 \fICharging (determination of collection charges)\fR \fIin the international telephone service\fR . .LP CCITT Rec. E.500 \fIMeasurement and recording of traffic\fR . .LP CCITT Rec. E.521 \fICalculation of the number of circuits in a group\fR \fIcarrying overflow traffic\fR . .LP CCITT Rec. E.543 \fIGrades of service in analogue/digital international\fR \fItelephone exchanges\fR . .LP CCITT Rec. E.410, E.411, E.412 and E.413 \fINetwork management\fR . .LP CCITT Series E. Recommendations Supplement No. 1 \fIList of possible\fR \fIsupplementary telephone services which may be offered to subscribers\fR . .LP CCITT Series E. Recommendations Supplement No. 2 \fIVarious tones\fR \fIused in national networks\fR . .LP CCITT Recs. G.120\(hyG.123 \fIGeneral characteristics of national systems\fR \fIforming part of international connections\fR . .LP CCITT Rec. G.121 \fICorrected reference equivalents (CREs) of\fR \fInational systems\fR . .LP CCITT Rec. G.122 \fIInfluence of national networks on stability and\fR \fIecho losses in national systems\fR . .bp .LP CCITT Rec. G.123 \fICircuit noise in national networks\fR . .LP CCITT Rec. G.231 (2) \fIUse of standard components in transmission\fR \fIequipment\fR . .LP CCITT Rec. G.703 \fIGeneral aspects of interfaces\fR . .LP CCITT Rec. G.704 \fIFunctional characteristics of interfaces associated with\fR \fInetwork nodes\fR . .LP CCITT Rec. G.705 \fICharacteristics required to terminate digital paths on a\fR \fIdigital exchange\fR . .LP CCITT Recs. G.731\(hyG.739 \fIPrincipal characteristics of primary\fR \fImultiplex equipment\fR . .LP CCITT Recs. G.741\(hyG.746 \fIPrincipal characteristics of second order\fR \fImultiplex equipments\fR . .LP CCITT Rec. G.811 \fIPerformance of clocks suitable for plesiochronous\fR \fIoperation of international digital links\fR . .LP CCITT Rec. G.822 \fIControlled slip rate objectives on an international\fR \fIdigital connection\fR . .LP CCITT Rec. I.412 \fIISDN user\(hynetwork interfaces\(hychannel structures and\fR \fIaccess capabilities\fR . .LP CCITT Rec. M.565 \fIAccess point for international telephone circuits\fR . .LP CCITT Rec. O.22 \fISpecification for the CCITT automatic transmission\fR \fImeasuring and signalling testing equipment ATME No.\ 2\fR . .LP CCITT Rec. Q.7 \fISignalling systems to be used for international\fR \fIautomatic and semi\(hyautomatic telephone working\fR . .LP CCITT Rec. Q.12 \fIOverflow\(hyalternative routing \(em rerouting \(em\fR \fIautomatic repeat attempt\fR . .LP CCITT Rec. Q.14 \fIMeans to control the number of satellite links in an\fR \fIinternational telephone connection\fR . .LP CCITT Rec. Q.15 \fINominal mean power during the busy hour\fR . .LP CCITT Rec. Q.16 \fIMaximum permissible value for the absolute power\fR \fIlevel of a signalling pulse\fR . .LP CCITT Rec. Q.21 \fISystems recommended for out\(hyband signalling\fR . .LP CCITT Rec. Q.23 \fITechnical features of push\(hybutton telephone sets\fR . .LP CCITT Rec. Q.24 \fIMulti\(hyfrequency push\(hybutton signal reception\fR . .LP CCITT Rec. Q.33 \fIProtection against the effects of faulty transmission on\fR \fIgroups of circuits\fR . .LP CCITT Rec. Q.35 \fICharacteristics of the dial tone, ringing tone,\fR \fIbusy tone, congestion tone, special information tone and warning tone\fR . .LP CCITT Rec. Q.45 \fITransmission characteristics of an international\fR \fIexchange\fR . .LP CCITT Rec. Q.48 \fIDemand assignment signalling systems\fR . .LP CCITT Rec. Q.49 \fISpecification for the CCITT automatic transmission\fR \fImeasuring and signalling testing equipment ATME No.\ 2\fR . .LP CCITT Recs. Q.101\(hyQ.103, Q.105\(hyQ.118 \fIbis Clauses applicable to CCITT\fR \fIstandard systems\fR . .LP CCITT Rec. Q.103 \fINumbering used\fR . .LP CCITT Rec. Q.105 \fINational (significant) number\fR . .LP CCITT Rec. Q.106 \fIThe sending\(hyfinished signal\fR . .LP CCITT Rec. Q.107 \fIStandard sending sequence of forward address\fR \fIinformation\fR . .LP CCITT Rec. Q.107 \fIbis Analysis of forward address information\fR \fIfor routing\fR . .LP CCITT Rec. Q.108 \fIOne\(hyway or both\(hyway operation of international\fR \fIcircuits\fR . .bp .LP CCITT Rec. Q.110 \fIGeneral aspects of the utilization of\fR \fIstandardized CCITT signalling systems on PCM links\fR . .LP CCITT Rec. Q.115 \fIControl of echo suppressors\fR . .LP CCITT Recs. Q.118 \fISpecial release arrangements\fR . .LP CCITT Recs. Q.251\(hyQ.300 \fISpecifications of Signalling System No. 6\fR . .LP CCITT Rec. Q.263 \fIDouble seizing with both\(hyway operation\fR . .LP CCITT Recs. Q.310\(hyQ.331 \fISpecifications of Signalling System R1\fR . .LP CCITT Recs. Q.400\(hyQ.490 \fISpecifications of Signalling System R2\fR . .LP CCITT Recs. Q.500\(hyQ.554 \fIDigital local, transit, combined and\fR \fIinternational exchanges in integrated digital networks and mixed\fR \fIanalogue\(hydigital networks\fR . .LP CCITT Recs. Q.601\(hyQ.685 \fIInterworking of signalling systems\fR . .LP CCITT Recs. Q.701\(hyQ.795 \fISpecifications of Signalling System No. 7\fR . .LP CCITT Rec. Q.920 \fIISDN user\(hynetwork interface data link layer \(em General\fR \fIaspects\fR . .LP CCITT Rec. Q.921 \fIISDN user\(hynetwork interface data link layer\fR \fIspecification\fR . .LP CCITT Rec. Q.930 \fIISDN user\(hynetwork interface layer\ 3 \(em General aspects\fR . .LP CCITT Rec. Q.931 \fIISDN user\(hynetwork interface layer\ 3 specification for basic call control\fR . .LP CCITT Series Q. Recommendations Supplement No. 3 \fIInformation\fR \fIreceived on national voice\(hyfrequency signalling systems\fR . .LP CCITT Rec. Z.100 Series \fIFunctional specification and description\fR \fIlanguage (SDL)\fR . .LP CCITT Rec. Z.200 Series \fICCITT high level language (CHILL)\fR . .LP CCITT Rec. Z.300 Series \fIMan\(hymachine language (MML)\fR . .LP CCITT Recs. Z.301\(hyZ.302 \fIGeneral principles\fR . .LP CCITT Rec. Z.301 \fIIntroduction to the CCITT man\(hymachine language\fR . .LP CCITT Recs. Z.311\(hyZ.317 \fIBasic syntax and dialogue procedures\fR . .LP CCITT Recs. Z.321\(hyZ.323 \fIExtended MML for visual display terminals\fR . .LP CCITT Recs. Z.331\(hyZ.333 \fISpecification of man\(hymachine\fR \fIinterface\fR . .bp .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation Q.4) .sp 9p .RT .ce 0 .ce 1000 \fBList of possible subscriber services and facilities\fR .sp 1P .RT .ce 0 .LP Subscriber services .sp 1P .RT .sp 1P .LP \fIBasic services\fR \v'3p' .sp 9p .RT .LP \(em subscriber dialled local, long distance, and international calling with automatic charging .LP \(em PBX line hunting, night service, and direct dialling\(hyin .LP \(em payphone .LP \(em access to operators for assistance and information .LP \(em access to community services (police, fire brigade, etc.) .LP \(em access to recorded announcements .LP \(em call barring .LP \(em malicious call trace .LP \(em interception of calls .LP \(em absent subscriber .LP \(em line observation .sp 1P .LP \fISupplementary services\fR \v'3p' .sp 9p .RT .LP \(em abbreviated dialling .LP \(em alarm call .LP \(em hot line .LP \(em outgoing service restriction .LP \(em call diversion .LP \(em call waiting .LP \(em do not disturb .LP \(em call completion to busy subscribers .LP \(em switching\(hyin not permitted .LP \(em call charge indicator at subscriber's premises .LP \(em immediate call charge announcement .LP \(em priority line .LP \(em two party line .LP \(em multiparty line .LP \(em multifrequency push\(hybutton (MFPB) dialling .LP \(em mobile subscriber .LP \(em conference service .LP \(em Centrex services .LP \(em other services .LP .rs .sp 8P .LP .bp .sp 2P .LP \fBRecommendation\ Q.5\fR .RT .sp 2P .ce 1000 \fBADVANTAGES\ OF\ SEMI\(hyAUTOMATIC\ SERVICE\fR .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.5'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.5 %' .ce 0 .sp 1P .ce 1000 \fBIN\ THE\ INTERNATIONAL\ TELEPHONE\ SERVICE\fR .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1954)\fR .sp 9p .RT .ce 0 .sp 1P .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (a) the large economies in personnel that can result from the introduction of semi\(hyautomatic service at the incoming exchange; .PP (b) the very small number of faults due to the equipment used for the international semi\(hyautomatic service; .PP (c) the improvement in the \*Qefficiency\*U (ratio of chargeable time to total holding time) of circuits using semi\(hyautomatic service compared with the efficiency of manual circuits operated on a demand basis; .PP (d) the improvement in the quality of the service given to users due to the reduction in the time of setting up a call; .PP (e) the fact that any type of call can be set up without difficulty over semi\(hyautomatic circuits, so that semi\(hyautomatic circuits can be used exclusively on an international relation; .sp 1P .LP \fIdraws the attention\fR | f Administrations .sp 9p .RT .PP to the advantages of semi\(hyautomatic service from the point of view of economy and of the quality of service given to subscribers. .LP .sp 2P .LP \fBRecommendation\ Q.6\fR .RT .sp 2P .sp 1P .ce 1000 \fBADVANTAGES\ OF\ INTERNATIONAL\ AUTOMATIC\ WORKING\fR .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.6'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.6 %' .ce 0 .sp 1P .ce 1000 \fI(New Delhi, 1960)\fR .sp 9p .RT .ce 0 .sp 1P .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (a) that the advantages of semi\(hyautomatic working mentioned in Recommendation\ Q.5 apply as well to automatic working in respect of reliability, circuit efficiency and the satisfaction given to subscribers; .PP (b) that the advantages of automatic working are even greater as regards staff economy, since outgoing operators are dispensed with; .PP (c) that the changeover from semi\(hyautomatic to automatic working may be accomplished without any major modification to the international circuits or to the switching equipment at transit and incoming .LP exchanges; .PP (d) that by 1960 the above advantages had been widely confirmed by experience on a number of international relations which had been using automatic service up to that time; .PP (e) that such experience has also shown that when a relation changes from demand working (manual or semi\(hyautomatic) to automatic working, there is a considerable increase in traffic; .PP (f ) that the introduction of an international automatic service follows logically on the introduction of a national automatic service; .sp 1P .LP \fIdraws the attention\fR | f Administrations .sp 9p .RT .PP to the additional advantages resulting from the introduction of an international automatic service. .bp .LP .sp 2P .LP \fBRecommendation\ Q.7\fR .RT .sp 2P .ce 1000 \fBSIGNALLING\ SYSTEMS\ TO\ BE\ USED\ FOR\ INTERNATIONAL\ AUTOMATIC\fR .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.7'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.7 %' .ce 0 .sp 1P .ce 1000 \fBAND\ SEMI\(hyAUTOMATIC\ TELEPHONE\ WORKING\fR .ce 0 .sp 1P .ce 1000 \fI(Geneva, 1954 and 1964, Mar del Plata, 1968,\fR .sp 9p .RT .ce 0 .sp 1P .ce 1000 \fIGeneva, 1976 and 1980)\fR .ce 0 .sp 1P .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (a) that standardization of the signalling systems to be used for international automatic and semi\(hy automatic telephone working is necessary to keep to a minimum the number of different types of equipment serving the various routes at any one exchange; .LP .PP (b) that the following signalling systems have been standardized and are applicable for \fIgeneral use\fR in international automatic and semi\(hyautomatic working: .LP \(em Signalling System No.\ 4, standardized by the CCIF in\ 1954; .LP \(em Signalling System No.\ 5, standardized by the CCITT in 1964; .LP \(em Signalling System No.\ 6, standardized by the CCITT in\ 1968; .LP \(em Signalling System No.\ 7, standardized by the CCITT in\ 1980; .LP .PP (c) that the following signalling systems have been standardized and are applicable for \fIregional use\fR in international automatic and semi\(hyautomatic telephone working: .LP \(em Signalling System R1 (Regional Signalling System No. 1, formerly called the North American System), standardized by the CCITT in 1968; .LP \(em Signalling System R2 (Regional Signalling System No. 2, formerly called the MFC Bern System), standardized by the CCITT in 1968; .PP (d) that, under the conditions and subject to the reservations stated below, these signalling systems may be expected to give acceptable results for international automatic and semi\(hyautomatic telephone working; .sp 1P .LP \fIdesiring\fR .sp 9p .RT .PP that the CCITT Recommendation concerning the signalling systems for international automatic and semi\(hyautomatic telephone working be generally applied by all Administrations; .sp 1P .LP \fIunanimously recommends\fR .sp 9p .RT .PP that, under the conditions and subject to the reservations stated below, Administrations should use, for international automatic and semi\(hyautomatic telephone working, one or more of the standard signalling systems mentioned in\ (b) and\ (c) above. .LP .sp 2P .LP \fB1\fR \fBCriteria for selecting a signalling system\fR .sp 1P .RT .PP Many factors influence the selection of a given signalling system for a particular application. Factors that should be considered include: .RT .PP 1.1 \fISatellite systems\fR | ecause of long round\(hytrip propagation delays (540\ \(+-\ 40 ms) .sp 9p .RT .PP The inclusion of one satellite link in a telephone connection requires subscribers to keep more discipline than usual during a conversation. If use is made of two satellite links in tandem, requirements are even more stringent. In addition, there is the question of what transmission objectives are attainable on such a connection. .bp .PP According to Recommendation Q.13 the inclusion of two satellite links in a connection should be avoided in all but exceptional cases. To facilitate the observance of this Recommendation, it is advisable to inform the subsequent transit centres by means of signalling that a satellite link is already included in the connection. During the following routing process the transit centre(s) should select a terrestrial link. .RT .LP .sp 1P .LP 1.2 \fIEcho suppressors\fR .sp 9p .RT .PP Both long terrestrial telephone links and satellite links call for the insertion of echo suppressors. Recommendations\ G.131\ [1] and\ Q.115 include basic requirements for the insertion of echo suppressors. .PP Therefore, signalling systems should be arranged to act in cooperation with switching equipment to achieve the goals covered by Recommendations\ G.131\ [1] and\ Q.115. This would be facilitated where the signalling system to be used provides the possibility of controlling the inclusion of echo suppressors. .PP In the future, the use of echo cancellers may need to be considered (see Recommendation\ G.165\ [2]). .RT .sp 1P .LP 1.3 \fISpeech interpolation systems (e.g. TASI)\fR .sp 9p .RT .PP In the case of a transmission system with speech interpolation, it must be ensured that the signalling system to be used is compatible with speech interpolation. .RT .LP .sp 2P .LP \fB2\fR \fBFurther criteria for selecting a signalling system\fR .sp 1P .RT .PP Once Administrations decide to establish a route, they will have to specify the general requirements to be met by the signalling system. .PP In the following, some questions are drawn up which may serve as a guideline: .RT .LP a) Does the transmission system provide for sufficient bandwidth (e.g. for outband line signalling)? .LP b) Is the signal capacity sufficient to allow the setting\(hyup of an ordinary connection? .LP c) Is an additional exchange of information required, e.g.: .LP \(em for echo suppressor control, .LP \(em to increase routing facilities, .LP \(em to obtain or to offer detailed information on congestion, .LP \(em to obtain or to offer information on the condition of the called subscriber line, .LP \(em to obtain or to offer information on the nature of the call: .LP i) for identification or .LP ii) for management purposes? .LP d) What requirements have to be set for the speed of the signalling system? What post\(hydialling and answering delays are to be tolerated? .LP e) Is there any interdependence between the minimum bundle size and signalling (e.g., as in the case of pilot interruption control of Signalling System\ R2)? .LP \fI\fR f ) In the case of satellite systems, does the earth station require an extra interface between the terrestrial access circuits and the satellite links? .LP g) Is it necessary to introduce a new signalling system? .LP h) Is the signalling system suitable for application to the particular exchange type, e.g., electro\(hy mechanical exchanges? .bp .sp 2P .LP \fB3\fR \fBCharacteristics of the standard CCITT Signalling Systems for\fR \fBgeneral use\fR .sp 1P .RT .sp 1P .LP 3.1 \fISignalling System No. 4\fR .sp 9p .RT .PP Described and specified in Fascicle\ VI.2. .PP Suitable for one\(hyway operation. .PP Suitable for terminal and transit working; in the latter case two or three circuits equipped with Signalling System No.\ 4 may be switched in tandem. .PP Signalling System No. 4 is used in Europe and the Mediterranean Basin. .PP It makes use of a two\(hyfrequency code within the speech band. .PP A four\(hyelement binary code is employed for interregister signalling. Each of these elements consists of one of the two signal frequencies. .PP Each digit is acknowledged. In the case of long propagation times, these acknowledgements have an adverse effect because the propagation time is included twice in one signalling cycle. This disadvantage is more or less compensated for by the overlap mode of operation. .PP Signalling System No. 4 has a signal capacity of 16 codes for forward interregister signals and no register signals in the backward direction other than the acknowledgement signals. .PP One signal is provided for echo suppressor control on mutual agreement. .PP A signal is not provided to indicate whether the connection already includes a satellite link. .PP Not suitable for operation on transmission systems with speech interpolation. .RT .sp 1P .LP 3.2 \fISignalling System No. 5\fR .sp 9p .RT .PP Described and specified in Fascicle\ VI.2. .PP Suitable for both\(hyway operation. .PP Suitable for terminal and transit working; in the latter case two or three circuits equipped with Signalling System No. 5 may be switched in tandem. .PP A multifrequency code (MFC: 2 out of 6) within the speech band is used for interregister signalling. The line signals consist of\ 1 or 2\ frequencies within the speech band. .PP The entire address information is stored up to the last signal. It is then transmitted en bloc as a rapid sequence of pulsed multifrequency code signals. .PP The application of the en bloc mode of operation may result in an increased post\(hydialling delay, especially if the ST\ condition is determined by time out. .PP Signalling System No. 5 has a signal capacity of 15\ codes for forward interregister signals and no backward interregister signals. .PP Signals are not provided either for echo suppressor control or for indicating whether the connection already includes a satellite link. .PP Suitable for operation on transmission systems with speech interpolation and on satellite links. .RT .LP .sp 1P .LP 3.3 \fISignalling System R1\fR .sp 9p .RT .PP Described and specified in Fascicle\ VI.4. .PP Signalling System R1 is mainly used in North America. .PP Suitable for both\(hyway operation. .PP Specified for terminal working. .PP A multifrequency code (MFC: 2 out of 6) within the speech band is used for interregister signalling. .PP In the analogue version of the Signalling System R1 line signalling, one frequency within the speech band is used. In the digital version of the Signalling System R1 line signalling, the two resultant signalling channels per speech circuit may be regarded as outband channels. .PP The following three modes of operation can be used to transmit the address information: .RT .LP \(em en bloc, .LP \(em en bloc/overlap, or .LP \(em overlap. .bp .PP The mode of operation selected influences: .LP \(em the seizing time of the next link, as well as .LP \(em the post\(hydialling delay. .LP .PP The address information is transmitted as pulsed MFC signals. .PP Signalling System R1 has a signal capacity of 15 codes for forward interregister signals but no backward interregister signals. .PP Signals are not provided either for echo suppressor control or for indicating whether the connection already includes a satellite link. .PP Signalling System R1 can be used on satellite links. A variant of Signalling System\ R1 may be suitable for operation on transmission systems with digital speech interpolation, provided that the systems are designed and engineered to be transparent to pulsed interregister signals. .RT .sp 1P .LP 3.4 \fISignalling System R2\fR .sp 9p .RT .PP Described and specified in Fascicle\ VI.4. .PP Used for one\(hyway operation on analogue transmission systems. Both\(hyway operation is possible on digital transmission systems. .PP Suitable for terminal and transit working. .PP Signalling System R2 is used in both national and international telephone networks in several regions of the world. .PP A multifrequency code (MFC: 2 out of 6) within the speech band is used for interregister signalling. Since two different sets of six frequencies in separate bands are defined for forward and backward interregister signals, Signalling System\ R2 interregister signalling is suitable for use on 2\(hywire circuits as well as on 4\(hywire circuits. .PP For the analogue version of the Signalling System R2 line signalling, use is made of a low\(hylevel tone\(hyon\(hyidle method out of band. In addition, pilot interruption control is used. .PP The digital version of the line signalling uses two signalling channels to transmit the signalling information and for circuit supervision. For 2048\ kbit/s PCM systems, the signalling information of the 30\ speech circuits is transmitted in the Time Slot\ 16 (see Recommendation\ G.732\ [3]). .PP It should be noted that the analogue version of the line signalling can be used on digital links; the signalling states are sent coded on one signalling channel. This use of the analogue version on digital links is not recommended on international circuits. .PP When a circuit is composed of both digital and analogue links, a conversion between the two versions of the line signalling can occur at the interface (see Recommendation\ Q.430). .PP Compelled signalling is used to transmit the address information in the overlap mode as multifrequency code signals, i.e., each forward interregister signal is acknowledged by a backward interregister signal. Considering that four\ times the propagation time is to be included in one signalling cycle, the exchange of signals is rather slow if the propagation time is long. This disadvantage is more or less compensated for by the overlap mode of operation. .PP Signalling System R2 has a higher signalling capacity than Signalling Systems\ No.\ 4, No.\ 5 and\ R1. The interregister signals allow, amongst others: .RT .LP \(em improved routing, .LP \(em detailed information on congestion, .LP \(em information on: .LP i) the nature of call, .LP ii) the condition of the called subscriber line, .LP \(em no\(hycharge calls, and .LP \(em address\(hycomplete information. .PP Signalling System R2 includes both forward and backward interregister signals for echo suppressor control. .bp .PP In Signalling System R2, two signals are specified which indicate whether \fIor not\fR | he connection already includes a satellite link. .PP Signalling System R2 may be suitable for use on satellite circuits, especially when it is already employed in the national or regional telephone networks concerned. .PP When Signalling System R2 is to be used on satellite links, the following must be borne in mind: .RT .LP \(em In the case of analogue line signalling, intervals T1 and T2 have to be adapted. .LP \(em Pilot interruption control requires bundles comprising a multiple of 12\ speech circuits. .LP \(em The register at the incoming end of a satellite link using Signalling System R2 shall be operated as an outgoing R2 register. .LP \(em The guard time for blocking and recognition of forward signals when pulsed signals are transmitted should be adapted to the propagation time on the satellite link. .PP Signalling System R2 may be suitable for operation on transmission systems with digital speech interpolation, provided the systems are designed and engineered to be transparent to pulsed interregister signals. .PP With 3 kHz spaced channels, the interregister signalling of Signalling System\ R2 may be used with the line signalling of Signalling System\ No.\ 4. .RT .sp 1P .LP 3.5 \fISignalling System No. 6\fR .sp 9p .RT .PP Fully described and specified in Fascicle\ VI.3. .PP Suitable for both\(hyway operation. .PP Suitable for terminal and transit working. .PP During the period from 1970 to 1972 Signalling System No. 6 was tested internationally. .PP Some Administrations have introduced it for international telephone traffic. A variant of Signalling System No. 6 is employed in the national telephone network of the United States. .PP A common signalling link is used for signalling. .PP May be used in either an associated or quasi\(hyassociated mode of operation. Use in a quasi\(hyassociated mode may be more economic for small bundles of circuits. .PP Signalling is performed by means of signal units. Each unit is 28\ bits in length, including 8\ check bits. Transmission is at a speed of 2400\ bit/s .PP for the analogue version and 4\ kbit/s (optionally 56\ kbit/s) for the digital version. .PP Each signal unit within a block of 11\ signal units is acknowledged and retransmitted in case of errors. .PP The address information can be transmitted en bloc and in the overlap mode. Because the transmission speed of Signalling System No.\ 6 is considerably higher than that of channel\(hyassociated signalling systems, the influence of the mode of operation on the post\(hydialling delay is reduced substantially. .PP The signal capacity (including the spare codes) of Signalling System\ No.\ 6 is much higher than that of Signalling Systems\ No.\ 4, No.\ 5, R1\ and\ R2. .PP Signalling System No.\ 6 contains signals for echo suppressor control as well as signals indicating whether a satellite link is already included in the connection. .PP Signalling System No.\ 6 can be used for all types of telephone circuits including those with speech interpolation. .PP Signalling System No.\ 6 can be used on satellite links. .RT .LP .sp 1P .LP 3.6 \fISignalling System No. 7\fR .sp 9p .RT .PP Fully described and specified in Fascicles\ VI.7, VI.8 and\ VI.9. .PP Suitable for both\(hyway operation. .PP Suitable for terminal and transit working. .PP A common signalling link is used for signalling. .PP Signalling System No. 7 can be used in national and international telecommunication networks. .bp .PP Signalling System No. 7 can be used for dedicated networks (e.g.\ data transmission, telephone) and within an integrated services digital network. It is the preferred signalling system between Integrated Digital Network (IDN) exchanges and within the Integrated Services Digital Network (ISDN). .PP Signalling System No. 7 may be used in either an associated or quasi\(hyassociated mode of operation. Use in a quasi\(hyassociated mode may be more economical for small bundles of circuits. .PP Variable length signal units with an integer number of octets are used of which 6\ perform message transfer part functions. Signalling System\ No.\ 7 is optimized for a digital bearer with transmission speed of 64\ kbit/s, but operation at lower speeds (e.g.\ 4.8\ kbit/s) on analogue bearers is possible. .PP Two error control methods (basic and preventive cyclic retransmission) are specified, each with its own field of application. In the basic method each signal unit is acknowledged and retransmitted in case of errors while in the preventive cyclic retransmission method no negative acknowledgements occur and error correction is performed by retransmission during idle periods of not yet acknowledged signal units. .PP The address information can be transmitted en bloc and in the overlap mode. Because the transmission speed of Signalling System\ No.\ 7 is considerably higher than that of channel\(hyassociated signalling systems, the influence of the mode of operation on the post\(hydialling delay is reduced substantially. .PP The signal capacity (including the spare codes) of Signalling System\ No.\ 7 is much higher than that of Signalling Systems\ No.\ 4, No.\ 5, R1 and\ R2. .PP Signalling System\ No.\ 7 contains signals for echo suppressor control as well as signals indicating whether a satellite link is already included in the connection. .PP Signalling System\ No.\ 7 can be used for all types of telephone circuits including those with speech interpolation. .PP Signalling System\ No.\ 7 can be used on satellite links. .RT .LP .sp 2P .LP \fBReferences\fR .sp 1P .RT .LP [1] CCITT Recommendation \fIStability and echo\fR , Vol.\ III, Rec.\ G.131. .LP [2] CCITT Recommendation \fIEcho cancellers\fR , Vol.\ III, Rec.\ G.165. .LP [3] CCITT Recommendation \fICharacteristics of primary PCM multiplex\fR \fIequipment operating at\ 2048 kbit/s\fR , Vol.\ III, Rec.\ G.732. .sp 2P .LP \fBRecommendation\ Q.8\fR .RT .sp 2P .ce 1000 \fBSIGNALLING\ SYSTEMS\ TO\ BE\ USED\ FOR\ INTERNATIONAL\ MANUAL\fR .EF '% Fascicle\ VI.1\ \(em\ Rec.\ Q.8'' .OF '''Fascicle\ VI.1\ \(em\ Rec.\ Q.8 %' .ce 0 .sp 1P .ce 1000 \fBAND\ AUTOMATIC\ WORKING\ ON\ ANALOGUE\ LEASED\ CIRCUITS\fR .ce 0 .sp 1P .sp 2P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (a) that standardization of signalling systems to be used for international manual and automatic working on analogue leased circuits brings advantages to Administrations, manufacturers and users; .PP (b) that manual and automatic operation of international leased circuits require different technical arrangements; .PP (c) that the standard signalling systems set out in Recommendation\ Q.7 are primarily intended for the public service; .PP (d) that the national circuit sections of international leased circuits may need to conform to local regulations of the Administration(s) concerned; .PP (e) that the method of signalling will be affected by the type of transmission and vice versa; .PP (f ) that the method of signalling will be affected by the characteristics of the service(s) carried on the circuit; .bp .sp 1P .LP \fIrecommends\fR .sp 9p .RT .PP that Administrations should use for manual international analogue leased circuits the standard signalling system specified in \(sc\ 1 below; .sp 1P .LP and \fIdraws the attention\fR | f Administrations .sp 9p .RT .PP to the guidance clauses and related annexes concerning automatic signalling on international analogue leased circuits, as set out in \(sc\ 2 below. .sp 2P .LP \fB1\fR \fBSignalling on manual international analogue leased circuits\fR .sp 1P .RT .PP 1.1 Signalling shall take place by the transmission of a single frequency signalling current, analogous to the signalling method used in the international manual service and specified in Recommendations\ Q.1 and\ Q.2. .sp 9p .RT .PP 1.2 The signalling current shall have a nominal frequency of either 2280\ Hz or 2600\ Hz. One of these frequencies shall be chosen for both directions of transmission by bilateral agreement between the Administrations concerned. Failing such an agreement, each Administration shall determine which of the two frequencies it wishes to receive. .PP 1.3 The duration of the transmitted tone shall be between 300 ms and 2\ seconds. The upper limit of 2\ seconds allows the partial use of signalling equipment designed for 500/20\ Hz working according to Recommendation\ Q.1. .PP 1.4 The signal recognition time shall be between 100 ms and 200\ ms: .LP \(em The minimum duration of 100 ms has been chosen so as to avoid the recognition of false signals due to imitation by speech currents; .LP \(em The maximum duration of 200 ms has been chosen so as to allow a safe margin between this time and the minimum transmission time. .PP Exceptionally, a maximum signal recognition time of 1200 ms may be used where it is known that the transmitted signal has a 2\ second duration. Such arrangements allow the partial use of signalling equipment designed for 500/20\ Hz working according to Recommendation\ Q.1. .PP 1.5 Other technical clauses for 2280 Hz signalling are set out in Annex\ A to this Recommendation. .sp 9p .RT .PP 1.6 Other technical clauses for 2600 Hz signalling are set out in Annex\ B to this Recommendation. .sp 9p .RT .sp 2P .LP \fB2\fR \fBSignalling on automatic international analogue leased circuits\fR .sp 1P .RT .PP 2.1 This section refers to international analogue leased circuits employing automatic signalling. Such circuits are considered to form part of a private network extending across international frontiers and linking exchanges carrying out the switching function in a private network. The exchanges may be Private Automatic Branch Exchanges (PABXs). Private tandem exchanges, or switching equipments provided by the Administration to carry out switching functions in a private network. Where the exchanges are privately owned, part of the signalling function may be provided by the Administration. .sp 9p .RT .PP This Recommendation does not cover the case of international leased circuits directly connecting subscriber lines to remote switching equipment. However, most of the following text is equally applicable to this case. Annex\ D, \(sc\ D.3 and Annex\ E give further information on such signalling. .PP 2.2 Many Administrations have regulations concerning the use of signalling frequencies on leased circuits and these may apply to international leased circuits also. These regulations are intended to ensure non\(hyinterference between parts of the voice spectrum used for signalling and those available for use by subscriber apparatus. This does not create exceptional difficulties for manual working since the frequencies used (2280\ Hz, 2600\ Hz) can be converted to other acceptable frequencies at the Terminal International Centre. However, for automatic circuits it should be the aim to provide an uninterrupted path between the ends of the leased circuit. .sp 9p .RT .PP Some World regions have existing or proposed signalling systems which meet the regulatory arrangements in those regions and a summary of two such systems are given in Annexes\ C and\ D to this Recommendation. Administrations are invited to note these existing systems that may meet their needs for automatic signalling on analogue leased circuits. .bp .PP 2.3 In order to reduce the cost of providing leased circuits some inter\(hyregional leased circuits may be provided with various forms of bandwidth economizing systems, such as speech interpolation systems and digital voice compression. These systems usually have their own internal digital signalling capability and these are not covered by this Recommendation, except that the effect that speech interpolation equipment has on analogue signalling is discussed. .sp 9p .RT .PP 2.4 In the most general case, the choice of signalling and transmission in a private network will be determined by the availability of suitable equipment, and by the decisions of the network user and the Administrations concerned. The following sections give guidance on transmission factors which affect signalling, the important characteristics of signalling systems which could affect the choice of transmission medium, and the interaction between signalling and non\(hyvoice services. .sp 9p .RT .sp 1P .LP 2.5 \fITransmission factors\fR \v'3p' .sp 9p .RT .PP 2.5.1 Recommendations for the transmission characteristics of leased circuits forming part of a private telephone network are given in Recommendation\ G.171. .PP 2.5.2 Where large groups of circuits are concerned and the transmission multiplex equipment is on the renter's premises, it is advisable to protect against the effects of faulty transmission on groups of circuits. Recommendation\ Q.33 gives details of such measures. .sp 1P .LP 2.5.3 \fISatellite systems\fR \v'3p' .sp 9p .RT .LP i) Some signalling systems will not function correctly over satellite links since the long propagation delay (270\ \(+-\ 20\ ms one way) exceeds that assumed by the line signalling specification. Amongst the standard systems for public telephony, Signalling System\ R2 incorporates special precautions because of this delay. In addition the speed of multi\(hyfrequency compelled interregister signalling is affected, which may cause undesirable post\(hydialling delay. If signalling systems based on R2 are used in private networks then reference should be made to information contained in Recommendations\ Q.7 and\ Q.400 to\ Q.490. .LP ii) Consideration should be given to the possibility that two satellite links may, in some cases, need to be connected in tandem. Means to prevent this may also need to be considered. (Further information is contained in Recommendations\ E.171, G.131, Q.14 and\ Q.115.) .LP iii) If satellite links via Time Division Multiple Access Systems with Digital Speech Interpolation (TDMA/DSI) are used, then guidance on circuit supervision signalling arrangements can be found in Recommendation\ Q.33. However, Digital Non\(hyInterpolated (DNI) channels are usually assigned for leased circuits and these exhibit fewer problems for signalling. .LP iv) If satellite links via Single Channel Per Carrier (SCPC) systems are used, then it should be noted that these systems employ voice activated carriers for telephony type circuits. On transmission systems of this type, the use of tone\(hyon\(hyidle signalling systems should be avoided, since such signalling systems would override the voice activation feature of SCPC systems. .sp 1P .LP 2.5.4 \fIEcho control\fR .sp 9p .RT .PP Paragraph 9 of Recommendation G.171 should be observed concerning the location of echo control devices where these are required. All analogue channel associated signalling systems operate more effectively if the line signal receiver, and often the line signal sender also, are located on the line side of any echo control device. In addition, some signalling systems require echo control devices to be locally disabled during interregister signalling. For these reasons, the echo control device should be located at the private renter's premises and not the terminal international centre. .RT .sp 1P .LP 2.5.5 \fISpeech interpolation\fR .sp 9p .RT .PP Some signalling systems may not be compatible with speech interpolation systems for the following reasons: .RT .LP i) Signalling systems employing continuous state tone signalling will cause permanent operation of the speech detectors and thus permanent trunk to channel association. This prevents the correct operation of the interpolation process. .LP ii) The speech interpolation equipment may not be transparent to out\(hyband signalling. .bp .LP iii) The speech interpolation equipment may cause excessive clipping of pulse signals resulting in their non\(hyrecognition by the distant signalling equipment. .LP iv) The speech interpolation equipment may not provide sufficient speech detector hangover to allow the successful transmission of some signals, e.g.\ en bloc multi\(hyfrequency signals. .PP Information on the characteristics of some speech interpolation systems is given in Supplement No.\ 2 of Fascicle\ V1.1, though different systems may also be used on leased circuits. .PP In the case of continuous state tone signalling, compatibility with speech interpolation systems can be achieved by converting the tone signalling to interface with any in\(hybuilt signalling capability the system may provide. If the transmission difficulty only exists in the interregister signalling phase, then this can be obviated by the simultaneous transmission of a speech interpolation locking tone, e.g.\ 2800\ Hz. .PP Note that fully compelled signalling techniques are compatible with speech interpolation systems. .RT .sp 2P .LP 2.6 \fICharacteristics of signalling systems\fR .sp 1P .RT .sp 1P .LP 2.6.1 \fILine signalling systems\fR .sp 9p .RT .PP Analogue line signalling systems can be divided into in\(hyband and out\(hyband systems. In addition, two signalling techniques may be employed: pulse signalling or continuous signalling. .PP Information on the comparative advantages of in\(hyband and out\(hyband systems can be found in Recommendation\ Q.20. General requirements for signalling equipment are contained in Recommendations\ Q.112 to\ Q.114. .RT .LP i) \fIIn\(hyband systems\fR .LP According to Recommendation Q.22, signalling frequencies above 2000\ Hz should be used (but see also \(sc\(sc\ 2.7.1 and\ 2.7.2 below). .LP The preferred power level for in\(hyband signalling is \(em9\ dBm0 for pulsed signals and \(em20\ dBm0 for continuous signals (also see Recommendation\ Q.16). .LP In\(hyband systems require the use of a guarding characteristic to prevent false operation of the signalling equipment by speech currents. Even so, occasional receiver misoperation by speech can occur, and thus in the speech phase a suitable minimum signal recognition time should be chosen. .LP In\(hyband systems require the use of splitting techniques in order to confine the signalling frequencies to the link concerned, and this has an impact on minimum signal recognition times. Further information can be found in Recommendation\ Q.25. .LP If the leased circuit contains a digital transmission system in the terminal national section and this connects directly to a renter's digital PABX using a first order PCM system, then the detection of in\(hyband signalling requires digital filtering techniques. .LP ii) \fIOut\(hyband systems\fR .LP Recommendation G.171 does not provide for the use of out\(hyband signalling on leased circuits. Because of the frequencies used, out\(hyband signalling requires the use of a transparent 4\ kHz bandwidth between the two signalling equipments. Part of the signalling equipment is usually provided within the transmission equipment. .LP Nevertheless, where the required transmission facilities can be assured, out\(hyband signalling may provide a useful alternative to in\(hyband signalling. Preferred signalling frequencies and power levels for out\(hyband signalling are set out in Recommendation\ Q.21. .LP iii) \fIPulsed signalling\fR .LP Pulsed signalling allows a greater signal repertoire than continous signalling, but requires more complex signal recognition arrangements. In general, the signalling tone is recognized by the signal receiver but requires persistence checking and correlation with the circuit state before the signal is validated. .bp .LP iv) \fIContinuous signalling\fR .LP Usually continous signalling is arranged to operate with \*Q\fItone\(hyon\(hyidle\fR \*U. Such systems have the inherent advantage of allowing immediate identification of circuit availability. .LP Since only two signal states are available in each direction, the possible signal repertoire is lower than pulsed systems, but recognition arrangements are simpler. A single persistence timing is usually provided to validate changes of signalling state. .LP Where continuous in\(hyband signalling uses the \*Q\fItone\(hyon\fR \*U condition after the interregister signalling phase, means must be provided to prevent the calling or called parties from hearing the signalling tone without undue interference to the transmission of speech currents and tones. A band stop filter as used in Signalling System\ R1 (see Recommendation\ Q.313, \(sc\ 2.3.4) may be suitable. Alternatively, to obviate these difficulties, pulsed signalling could be used in the speech phase. .sp 1P .LP 2.6.2 \fIInterregister signalling\fR .sp 9p .RT .PP The following types of interregister signalling may be suitable for use on leased circuits: .RT .LP i) \fIDecadic signalling\fR .LP Signalling takes place using the same frequency and sender/receiver equipment as the line signalling. Forward signals are composed of a sequence of tone pulses analogous to subscriber line signalling employing rotary dials. Backward signals may not always be provided, but \fIproceed\(hyto\(hysend\fR and \fIaddress complete\fR signals can be used to advantage. .LP ii) \fIMulti\(hyfrequency signalling\fR .LP Multi\(hyfrequency (MF) signalling has the advantage of greater speed and signal repertoire than decadic systems. To provide both an adequate repertoire and signalling reliability, signals are composed of two frequencies from a set of\ 4, 5, 6 or 8\ frequencies. Different frequencies may be used for signalling in the backward direction. The frequencies used for MF signalling should lie below 2000\ Hz in order that they do not interfere with in\(hyband line signalling. .LP MF systems may transmit signals in pulse form, or in a compelled sequence with signals in the opposite direction. The preferred signal power level is \(em9\ dBm0 for each constituent tone. .LP Three existing MF systems may be suitable as the basis for signalling on leased circuits. These are: .LP 1) The dual tone multi\(hyfrequency system as specified in Recommendation Q.23 and modified to act as an interregister signalling system. (See also Recommendation\ Q.24.) .LP 2) Signalling System R1. See Recommendations Q.7 and Q.310 to\ Q.331. .LP 3) Signalling System R2. See Recommendations Q.7 and Q.400 to\ Q.490. .sp 1P .LP 2.6.3 \fIOverall signalling repertoire\fR .sp 9p .RT .PP Consideration should be given to providing a set of signals capable of being adapted for different situations to provide a signal capability for extending the scope of PABX supplementary services to encompass the private network as a whole, and to provide other network facilities. This is best achieved by the inclusion in the signalling repertoire of a set of auxiliary signals that are separate from the basic call set\(hyup and supervisory signals and can therefore be allocated in a flexible manner to the required function. .RT .sp 1P .LP 2.6.4 \fIPosition of signalling equipment\fR .sp 9p .RT .PP Normally all signalling equipment for automatic leased circuits will be located at the renter's premises. Some Administrations may wish or may be able to provide part of the signalling equipment at the Terminal National Centre or the Terminal International Centre. In these cases, suitable signalling arrangements need to be made to interconnect the exchange at the renter's premises with the remote elements of the signalling equipment. This will be determined by the Administration concerned. Any echo control device could in this case also be remote, but see Recommendation G.171, \(sc\ 9.2. .bp .RT .sp 1P .LP 2.7 \fIInteraction between signalling and non\(hyvoice services\fR .sp 9p .RT .PP As well as normal speech transmission, leased circuits can be used to provide for other types of service (see Recommendation\ M.1015). .PP The most common types are: .RT .LP \(em Voice\(hyfrequency telegraphy, .LP \(em Data transmission, .LP \(em Facsimile, .LP \(em Phototelegraphy. .PP Since these services use in\(hyband frequencies, there is a possibility of interaction with signalling, and the following general guidance is given below. .sp 1P .LP 2.7.1 \fIVoice\(hyfrequency telegraphy\fR .sp 9p .RT .PP Where voice\(hyfrequency telegraphy is carried on a telephone\(hytype leased circuit it will be by one of two methods: .RT .LP \(em \fIAlternate use\fR | see Recommendation M.1015). The circuit is switched at both ends between the telephone equipment and the photo\(hytelegraph equipment. .LP \(em Subdivision of the frequency band between telephone and telegraph services. (See Recommendation\ H.34.) .PP In the former case, the signalling equipment is disconnected during telegraph use and no interaction can take place. (Outgoing telephone circuits should be removed from service and blocked prior to service switching). .PP In the latter case, the in\(hyband telephone signalling must be confined to frequencies below 2500\ Hz since the attenuation at higher frequencies due to the separation filter cannot provide a reliable signalling path. .RT .sp 1P .LP 2.7.2 \fIData transmission\fR .sp 9p .RT .PP Data transmission systems for use over leased circuits are specified in Recommendations\ V.16, V.19 to\ V.23, V.26 and\ V.27. These systems do not interact with the Standard Systems for the following reasons: .RT .LP i) In most cases, the data carriers lie below 2000\ Hz and thus below the range for voice frequency line signalling. However, when the carrier is modulated, energy may be present in the signalling band but false receiver operation is prevented by there being at all times a greater energy in the pass\(hyband of the guard circuit. .LP ii) In some cases, the carriers do lie in the signalling band above 2000\ Hz, but with constant phase modulation the guard circuit will operate as outlined in\ i) above. In the case of 1200\ bits/sec duplex transmission according to Recommendation\ V.22, a guard tone of 1800\ Hz is required in order to ensure guard circuit operation. .PP For signalling systems on automatic leased circuits therefore, providing the signalling frequency is above 2000\ Hz and that a guard circuit with a pass\(hyband covering the common data carrier frequencies is used, no problems are foreseen with interaction. .PP In order that duplex data transmission can take place on circuits equipped with echo control devices, the data set will transmit a tone disabling signal with the following characteristics (see also Recommendation\ G.164). .PP 2100 \(+- | 5\ Hz at a level of \(em12 \(+- | \ dBm0 .PP Duration greater than 400\ ms .PP In order that false operation of signalling equipment does not take place, it is essential that the lowest possible operating frequency of the signalling receiver be above the highest possible tone disabling frequency. This requires that the lowest usable signalling frequency be higher than the 2000\ Hz referred to above in \(sc\ 2.6.1. .bp .PP \fR For example: .RT .ad r Highest tone disabling frequency =\ 2115 Hz Allowance for frequency deviation in channel =\ \ \ 5 Hz Margin of safety =\ \ 30 Hz Typical maximum receiver deviation for operation =\ \ 75 Hz \ 75 Hz Giving 2225 Hz .ad b .RT .PP Thus on the basis of this example, frequencies above 2225 Hz should be suitable for signalling. .PP Since the tone disabling circuit of echo control devices may respond in the range 1900\(hy2350\ Hz, the unintentional disabling of echo control devices may occur during signalling if this frequency range is used. However, this is not considered detrimental since the echo control device serves no essential function during the time when signalling tones are present on the circuit. .RT .sp 1P .LP 2.7.3 \fIFacsimile\fR .sp 9p .RT .PP Facsimile apparatus for use on telephone circuits are specified in Recommendations\ T.2, T.3,\ T.4 and\ T.10. .RT .LP i) \fIGroup 1 apparatus\fR | Recommendation T.2) .LP Since leased circuits in an automatic private network form part of a switched connection, the centre frequency \fIf\fR\d\fIo\fR\ushould be 1700\ Hz as used on the public switched network. This implies, for frequency modulation, a transmitted frequency between 1300\ Hz (white) and 2100\ Hz (black). With a maximum frequency deviation of 32\ Hz, and by analogy with the calculations in \(sc\ 2.7.2\ above, frequencies above 2242\ Hz should be suitable for signalling. This must be carefully observed since facsimile transmission may result in a single tone for a significant period, and without energy in the pass\(hyband of the guard circuit. .LP ii) \fIGroup 2 apparatus\fR | Recommendation T.3) .LP The transmission method for Group 2 machines uses vestigal sideband amplitude modulation. The 2100\ Hz carrier frequency is permanently modulated and the effect of this and the vestigial sideband filter is such that the energy spectrum of the transmitted signal is biased towards frequencies in the pass\(hyband of the guard circuit and receiver misoperation should not occur. .LP iii) \fIGroup 3 apparatus\fR | Recommendation T.4) .LP The transmission method for Group 3 machines uses the data transmission method of Recommendation\ V.27 | fIter\fR or\ V.29. False operation should not occur for the reasons described in \(sc\ 2.7.2 above. .sp 1P .LP 2.7.4 \fIPhototelegraphy\fR .sp 9p .RT .PP For Phototelegraphy on leased circuits, Recommendations T.1 and T.11 apply. .PP The transmitted centre frequency is 1900 Hz with deviation (in the case of frequency modulation) from 1500\ Hz (white) to 2300\ Hz (black). For amplitude modulated systems the carrier may be between\ 1300 and\ 1900\ Hz. .PP In many cases a phototelegraph circuit is derived by \fIalternate use\fR | here the telephone signalling equipment is disconnected. However, where automatic switching of phototelegraph circuits is required, the guidance of Recommendation\ T.11, \(sc\ 3.2 applies; that is, a guard tone (\fIblocking\fR \fIsignal\fR ) should be transmitted in order to prevent false receiver operation on single\(hyfrequency signalling systems. .RT .sp 1P .LP 2.7.5 \fIInterference of service signals\fR .sp 9p .RT .PP With the systems referred to in \(sc\(sc 2.7.1\(hy2.7.4 above, the precautions included to prevent false recognition of service signals will usually be reliable. However, where the precautions are dependent on the statistical probability of the transmitted power spectrum operating the guard circuit, there is always a small risk of receiver operation for very short periods (in a similar fashion to the occasional false operation by speech). It should be noted that if such operation persists long enough, then the receiver splitting function will operate and thus cause a discontinuity in the service signal. This should be borne in mind when deciding the minimum receiver splitting time. In the call connected phase it is advisable that the minimum tone recognition time for a valid signal should be chosen such that occasional short receiver operation does not cause a change of signalling state. .bp .RT .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation Q.8) .sp 9p .RT .ce 0 .ce 1000 \fBTechnical clauses for 2280 Hz signalling on manual circuits\fR .sp 1P .RT .ce 0 .LP A.1 \fISignal sender\fR .sp 1P .RT .sp 1P .LP A.1.1 \fISignalling frequency\fR .sp 9p .RT .PP 2280 \(+- | Hz. .RT .sp 1P .LP A.1.2 \fITransmitted signal level\fR .sp 9p .RT .PP \(em13 \(+- | dBm0. .PP The permissible noise level measured at the output of the signal sender shall be as low as practicable, but in any event at least 35\ dB below signal level. .PP The level of leak current transmitted to line should be at least 50\ dB below signal level. .RT .sp 2P .LP A.2 \fISignal receiver\fR .sp 1P .RT .sp 1P .LP A.2.1 \fIOperating limits\fR .sp 9p .RT .PP The signal receiver must operate satisfactorily if a signal is received satisfying the following conditions: .RT .LP a) the frequency received is within 2280 \(+- 15 Hz; .LP b) the absolute power level \fIN\fR of each unmodulated signal shall be within the limits (\(em19\ +\ \fIn\fR \ \(=\ \fIN\fR \ \(=\ \(em7\ +\ \fIn\fR )\ dBm where\ \fIn\fR is the relative power level at the receiver input. .PP The limits give a margin of \(+- | dB on the nominal absolute power level of the 2280\ Hz signal received at the receiver input, to allow for variations in transmission conditions on the international circuits. .sp 1P .LP A.2.2 \fINon\(hyoperate conditions\fR \v'3p' .sp 9p .RT .LP a) \fISelectivity\fR .LP The signal receiver shall not operate on a signal having an absolute power level at the receiving end within the limits specified in \(sc\ 2.1\ b) when the frequency is outside: 2280 \(+- | 5\ Hz. .LP b) \fIMaximum sensitivity of the signal receiver\fR .LP The signal receiver shall not operate on a signal in the range 2280\ \(+-\ 15\ Hz whose absolute power level at the point of connection of the receiver is (\(em29\ \(em13\ +\ \fIn\fR )\ dBm, \fIn\fR being the relative power level at this point. .sp 2P .LP A.2.3 \fIGuard circuit\fR .sp 1P .RT .sp 1P .LP A.2.3.1 \fIEfficiency of the guard circuit\fR .sp 9p .RT .PP The signal receiver must be protected by a guard circuit against false operation due to speech currents, circuit noise, or other currents of miscellaneous origin circulating in the line. .PP The purpose of the guard circuit is to prevent signal imitation, and operation of the splitting device by interfering speech. .PP To minimize signal imitation by speech current it is advisable that the guard circuit be tuned as follows: .PP To minimize signal interference by low\(hyfrequency noise it is advisable that the response of the guard circuit falls off towards the lower frequencies and that the sensitivity of the guard circuit at 200\ Hz is at least 10\ dB less than at\ 1000\ Hz. .bp .PP An indication of the efficiency of the guard circuit is given by the following: .RT .LP a) during 10 hours of speech, normal speech currents should not, on average, cause more than one false operation of the receiver lasting more than the minimum recognition time of the signal; .LP b) the number of false splits of the speech path caused by speech currents should not cause an appreciable reduction in the transmission quality of the circuit. .sp 1P .LP A.2.3.2 \fIGuard circuit limits\fR .sp 9p .RT .PP Considering: .RT .LP a) that unweighted noise of a level \(em40 dBm0 and uniform spectrum energy may arise on the longest international circuit; .LP b) that an oversensitive guard circuit might give rise to signalling difficulties. .PP It is recommended that, the guard circuit shall not operate in the presence of noise at a level of less than \(em35\ dBm0 and uniform spectral energy over the frequency range 300\(hy3400\ Hz. .sp 2P .LP A.3 \fISplitting arrangements\fR .sp 1P .RT .PP Sending and receiving line splitting shall be provided. .RT .sp 1P .LP A.3.1 \fISending line split\fR \v'3p' .sp 9p .RT .LP a) the sending line transmission path of the signalling termination shall be disconnected 30\(hy50\ ms before a voice\(hyfrequency signal is sent over the circuit; .LP b) the sending line transmission path of the signalling termination will not be reconnected for 30\(hy50\ ms following the end of the sending of a voice\(hyfrequency signal over the circuit. .sp 1P .LP A.3.2 \fIReceiving line split\fR \v'3p' .sp 9p .RT .LP a) the receiving line transmission path of the signalling termination shall be split when the 2280\ Hz signal is received. The splitting time should be less than 20\ ms; .LP b) the split must be maintained for the duration of the signal but must cease within 25\ ms of the cessation of the 2280\ Hz signal; .LP c) the splitting device may be any suitable arrangement for example, physical line disconnection, insertion of a bandstop filter,\ etc. The level of leak current transmitted to the subsequent circuit should be at least 40\ dB below the received signal level. .ce 1000 ANNEX\ B .ce 0 .ce 1000 (to Recommendation Q.8) .sp 9p .RT .ce 0 .ce 1000 \fBTechnical clauses for 2600 Hz signalling on manual circuits\fR .sp 1P .RT .ce 0 .LP B.1 \fISignalling sender\fR .sp 1P .RT .sp 1P .LP B.1.1 \fISignalling frequency\fR .sp 9p .RT .PP 2600 \(+- | Hz. .RT .sp 1P .LP B.1.2 \fITransmitted signal level\fR .sp 9p .RT .PP The transmitted signal level shall be \(em8 \(+- | dBm0 for the duration of the signal or for a minimum of 300\ ms (whichever is shorter) and for a maximum of 550\ ms after which the level of the signal shall be reduced to\ \(em20\ \(+- | \ dBm0. .RT .sp 1P .LP B.1.3 \fISignal frequency leak\fR .sp 9p .RT .PP The level of signal frequency leak power transmitted to the line should not exceed \(em70\ dBm0, during the tone\(hyoff condition. .bp .RT .sp 1P .LP B.1.4 \fIExtraneous frequency components\fR .sp 9p .RT .PP The total extraneous frequency components accompanying a tone signal should be at least 35\ dB below the fundamental signal power. .RT .sp 1P .LP B.1.5 \fISending line split\fR .sp 9p .RT .PP The following splitting arrangements are required when transmitting line signals to prevent incorrect operation of the receiving equipment: .RT .LP a) when a tone\(hyon signal is to be transmitted, the sending line transmission path shall be split, within an interval from 20\ ms before, to 5\ ms after tone is applied to the line, and remain split for a minimum of 350\ ms and a maximum of 750\ ms; .LP b) when a tone\(hyoff signal is to be transmitted, the sending line transmission path shall be split, within an interval from 20\ ms before, to 5\ ms after tone is removed from the line, and remain split for a minimum of 75\ ms and a maximum of 160\ ms after the tone is removed. .PP Further details are given in \(sc\ 2.2.6 of Recommendation\ Q.312. .sp 2P .LP B.2 \fISignal receiver\fR .sp 1P .RT .sp 1P .LP B.2.1 \fIOperating limits\fR .sp 9p .RT .PP The receiving equipment shall operate on a received tone signal that meets the conditions listed below: .RT .LP a) 2600 \(+- | 5 Hz; .LP b) to ensure proper operation in the presence of noise, the signal level of the initial portion of each tone\(hyon signal is augmented by 12\ dB. The absolute power level of the signal shall be within the limits (\(em27\ +\ \fIn\fR \ \(=\ \fIN\fR \ \(=\ \(em1\ +\ \fIn\fR )\ dBm where \fIn\fR is the relative power level at the input to the receiving equipment. .sp 1P .LP B.2.2 \fINon\(hyoperate limits\fR \v'3p' .sp 9p .RT .LP a) The receiving equipment shall neither operate on signals originating from subscriber stations (or other sources) if the total power in the band from 800\ Hz to 2450\ Hz equals or exceeds the total power present at the same time in the band from 2450\ Hz to 2750\ Hz as measured at the station, nor degrade these signals. .LP b) The receiving equipment shall not operate on any tone or signal whose absolute power level at the point of connection of the receiving equipment is (\(em17\ \(em20\ +\ \fIn\fR )\ dBm or less, \fIn\fR being the relative power level at this point. .PP On average during 10 hours of speech, normal speech currents should not cause more than one operation lasting more than 50\ ms. .sp 1P .LP B.2.3 \fIReceiving line split\fR .sp 9p .RT .PP To prevent line signals of the signalling system from causing disturbances to signalling systems on subsequent circuit sections, the receiving line transmission path should be split when the signal frequency is received to ensure that no portion of any signal exceeding 20\ ms duration may pass out of the circuit section. .PP This should be achieved by use of a bandstop filter in which case the level of signal leak current transmitted to the subsequent circuit section with the bandstop filter inserted should be at least 35\ dB below the received signal level. In addition, the bandstop filter must not introduce more than 5\ dB loss at frequencies 200\ Hz or more above or below the midband frequency nor more than 0.5 dB loss at frequencies 400\ Hz or more above or below the midband frequency. .PP The receiving line split must be maintained for the duration of the incoming tone signal, but must cease within 300\ ms of tone removal. .PP \fINote\fR \ \(em\ In some existing designs, the initial cut may be a physical line disconnection but the filter must be inserted within 100\ ms of tone reception. .bp .RT .ce 1000 ANNEX\ C .ce 0 .ce 1000 (to Recommendation Q.8) .sp 9p .RT .ce 0 .ce 1000 \fBThe\fR \fBstandard European inter\(hyPABX signalling system\fR .sp 1P .RT .ce 0 .LP C.1 \fIIntroduction\fR .sp 1P .RT .PP Recognizing the increasing use of leased lines between private automatic branch exchanges (PABXs) in the European telecommunication networks, a specification has been developed covering the need for signalling on such lines. The system emerged is called Signalling System\ L1. Distinction is made between line signalling (call supervisory signals) and interregister signalling (set\(hyup including routing and additional service control). Taking into account different applications, existing interregister signalling techniques have been adopted for use with the basic line signalling as follows: .RT .LP \(em decadic pulsing (DP); .LP \(em multi\(hyfrequency push\(hybutton (MFPB) type signalling; .LP \(em System R2 multi\(hyfrequency code (MFC) type signalling. .sp 1P .LP C.2 \fIPrinciples and field of application\fR \v'3p' .sp 9p .RT .PP C.2.1 The line signalling system is to provide automatic and semi\(hyautomatic working between PABXs in different countries. .PP C.2.2 The signalling system is a single voice frequency (1\ vf) tone\(hyon\(hyidle line signalling system using a signalling frequency of 2280\ Hz. The use of voice frequency signals renders the system suitable for all voice transmission media, except those using speech interpolation. .PP C.2.3 The system is intended for use on bothway inter\(hyPABX circuits, with first party clearing. .PP C.2.4 Either decadic pulsing or multi\(hyfrequency interregister signalling may be used with the line signalling system. The provision of particular line signals will depend upon the requirements of the associated interregister signalling system. .PP C.2.5 The system operates on a four\(hywire basis, forward and backward signals being segregated by utilizing the four\(hywire circuits as two separate signalling paths. .PP C.2.6 In addition to the application or removal of signalling frequency (tone\(hyon and tone\(hyoff) in continuous form, the transmission of pulses of signalling frequency is applied. .PP C.2.7 When in the idle condition, the signalling frequency applied to the line is reduced in power level to conform to the transmission loading requirements of Recommendation\ Q.15. .PP C.2.8 The line signalling operates on a link\(hyby\(hylink basis and may be used to establish a multi\(hylink tandem connection using one or more private automatic exchange(s) as a transit switch. In accordance with Recommendation\ Q.25 sending line and receiving line splitting arrangements are provided so that signals are contained within the appropriate link and are not allowed to spill over into subsequent or preceding links. .sp 1P .LP C.3 \fILine signal conditions and signalling codes\fR \v'3p' .sp 9p .RT .PP C.3.1 The line signal conditions and the signalling codes shall be as shown in Table\ C\(hy1/Q.8. Signal sending and detection requirements are given in \(sc\(sc\ C.3.2 and\ C.3.3. .PP C.3.2 A continuous tone\(hyon condition shall be the application of the signalling frequency to the send signalling path for a period exceeding 300\ ms. .sp 9p .RT .PP A tone\(hyon pulse signal shall be the application of the signalling frequency to the send signalling path for a period of 45\(hy135\ ms. A continuous tone\(hyoff condition shall exist when any signalling frequency is absent from the send signalling path for a period exceeding 80\ ms. .bp .ce \fBH.T. [T1.8]\fR .ce TABLE\ C\(hy1/Q.8 .ce \fBLine signal conditions and signalling codes\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(60p) | cw(84p) | cw(84p) . Signal From outgoing PABX From incoming PABX _ .T& lw(60p) | lw(84p) | lw(84p) . Idle Continuous tone\(hyon Continuous tone\(hyon .T& lw(60p) | lw(84p) | lw(84p) . Seizing Continuous tone\(hyoff Continuous tone\(hyon .T& lw(60p) | lw(84p) | lw(84p) . { Seizing\(hyacknowledgement or proceed\(hyto\(hysend } Continuous tone\(hyoff Continuous tone\(hyoff .T& lw(60p) | lw(84p) | lw(84p) . Answer Continuous tone\(hyoff Single tone\(hyon pulse .T& lw(60p) | lw(84p) | lw(84p) . Clear\(hyforward Continuous tone\(hyon { Continuous tone\(hyon or tone\(hyoff } .T& lw(60p) | lw(84p) | lw(84p) . Clear\(hyback Continuous tone\(hyoff Continuous tone\(hyon _ .TE .nr PS 9 .RT .ad r \fBTableau C\(hy1/Q.8 [T1.8] p. 3\fR .sp 1P .RT .ad b .RT .PP C.3.3 A tone\(hyon condition applied to the receive signalling path PABX termination may be recognized as a continuous tone\(hyon condition for signalling when it has persisted for 150\ ms, while for a tone\(hyoff condition a value of 40\ ms has to be taken into account. .sp 9p .RT .PP A tone\(hyon condition applied to the receive signalling path PABX termination and persisting for 35\(hy150\ ms, followed by a tone\(hyoff condition longer than 200\ ms, may be recognized as a pulse tone\(hyon signal. .sp 2P .LP C.4 \fILine signalling transmission requirements\fR .sp 1P .RT .sp 1P .LP C.4.1 \fISignal sender\fR \v'3p' .sp 9p .RT .PP C.4.1.1 The signalling tone shall be at a frequency of 2280 \(+- | Hz. .PP C.4.1.2 The tone\(hyon condition shall have two power levels: a high level and a low level. .PP A high level tone shall be sent for the duration of the signal or for a minimum of 300\ ms (whichever is shorter) and for a maximum of 550\ ms after which it must be reduced to low level. .LP a) A high level tone\(hyon condition shall be a signalling tone transmitted at a level of \(em10\ dBm0\ \(+- | \ dB. .LP b) A low level tone\(hyon condition shall be a signalling tone transmitted at a level of \(em20\ dBm0\ \(+- | \ dB. .sp 1P .LP C.4.2 \fISignal receiver\fR \v'3p' .sp 9p .RT .PP C.4.2.1 A frequency within the range 2280 \(+- 15 Hz at an absolute level\ \fIN\fR , within the range (\(em30\ +\ \fIn\fR \ \(=\ \fIN\fR \ \(=\ \(em4\ +\ \fIn\fR )\ dBm, shall be recognized as a tone\(hyon condition; where \fIn\fR is the relative power level at the receive signalling path PABX termination (see Recommendation\ G.171). .PP C.4.2.2 Any frequency or combination of frequencies having a total absolute power level or less than (\(em40\ +\ \fIn\fR )\ dBm shall be recognized as a tone\(hyoff condition; where \fIn\fR is the relative power level at the receive signalling path PABX termination as in \(sc\ C.4.2.1. .sp 1P .LP C.5 \fIGeneral line signal transfer procedures\fR \v'3p' .sp 9p .RT .PP C.5.1 Depending upon the capabilities of the incoming PABX, recognition of the seizing signal will initiate either proceed\(hyto\(hysend or seizing acknowledgement. The sending of the latter signal does not imply that the incoming PABX is ready to receive address information. .bp .PP C.5.2 Some PABXs do not use the answer signal, others require it for correct operation. Therefore the answer signal is optional and subject to mutual agreement. .PP C.5.3 A continuous tone\(hyon signal shall be applied when, after recognition of a seizing signal, no address or incomplete address information is received and the incoming PABX times\(hyout. .PP A continuous tone\(hyon signal may be applied when an incoming PABX encounters congestion or an engaged extension. .sp 1P .LP C.6 \fIDecadic pulsing\fR .sp 9p .RT .PP For decadic pulsing interregister signalling the 2280\ Hz line signalling is used. Some characteristics are given below. .RT .PP C.6.1 The break periods of dial pulses shall be applied to the send signalling path as pulses of tone\(hyon condition within the following limits. .sp 9p .RT .LP SPEED\ (pulses\ per\ sec.) .LP BREAK\ PULSE | | 11 12 .LP MIN MAX MIN MAX MIN MAX MIN MAX .LP DURATION\ (ms) .LP 45 112 45 81 45 61 45 52 .PP C.6.2 Pulses of tone\(hyon condition applied to the receive signalling path PABX termination and consistent with the following speed and duration limits, are break periods of dial pulses (address signal). .sp 9p .RT .LP SPEED\ (pulses\ per\ sec.) .LP BREAK\ PULSE | | 11 12 .LP MIN MAX MIN MAX MIN MAX MIN MAX .LP DURATION\ (ms) .LP 35 122 35 91 35 71 35 62 .ce 1000 ANNEX\ D .ce 0 .ce 1000 (to Recommendation Q.8) .sp 9p .RT .ce 0 .ce 1000 \fBA\fR \fBtypical North American private analogue network\fR .sp 1P .RT .ce 0 .ce 1000 \fBsignalling system\fR .ce 0 .LP D.1 \fIIntroduction\fR .sp 1P .RT .PP D.1.1 A Private Switched Network is a common control switching arrangement which provides interconnections of subscriber locations via dedicated access lines and inter\(hyexchange circuits and shared common control switching with the Public Switched Telephone Network. The Private Switched Networks are terminated at the subscriber location by directly\(hyhomed telephone sets, multi\(hyline telephone systems or by main PBX or PABXs. This annex describes the signalling on a typical North American switched private network. .sp 9p .RT .sp 1P .LP D.2 \fIGeneral signalling applications\fR \v'3p' .sp 9p .RT .PP D.2.1 The line signalling system provides for semi\(hyautomatic and automatic working between subscribers on the private network and the ability to go off network to the Public Switched Network. .PP D.2.2 In general, four\(hywire transmission links employing an in\(hyband single frequency of 2600\ Hz, tone\(hyon\(hyidle, are used on the inter\(hyexchange circuits, directly\(hyhomed stations and PBX access lines. .PP D.2.3 Signalling on an inter\(hyexchange circuit is in accordance with Recommendations\ Q.310 to Q.331 \(em System\ R1 signalling. .PP D.2.4 Either decadic pulsing (DP) or multi\(hyfrequency pushbutton is used for address signalling on access lines. .bp .PP D.2.5 Multi\(hyfrequency pushbutton signalling is in accordance with Recommendation\ Q.23. (See also Recommendation\ Q.24.) .PP D.2.6 Address signalling on inter\(hyexchange circuits is multi\(hyfrequency (MF) using a combination of two out of six frequencies in accordance with Recommendations\ Q.320 to\ Q.326. .PP D.2.7 Interregister signalling techniques are used for controlling outpulsing to accommodate different equipment designs and to improve register usage. .sp 1P .LP D.3 \fISignalling on access lines\fR \v'3p' .sp 9p .RT .PP D.3.1 Either decadic pulsing (DP) or multi\(hyfrequency push\(hybutton (MFPB) is used on access lines for address signalling. .PP D.3.2 Supervisory signalling may use either the single frequency 2600\ Hz or direct current loop. .PP D.3.3 Called party ringing is controlled by the terminating exchange or PABX in a conventional manner. .sp 1P .LP D.4 \fISignalling on inter\(hyexchange trunks\fR \v'3p' .sp 9p .RT .PP D.4.1 Supervisory signalling is single frequency 2600 Hz in accordance with Recommendations Q.310 to\ Q.313, Q.317 and\ Q.318. .PP D.4.2 Register signalling uses multi\(hyfrequency (MF) signals consisting of two out of six frequencies in accordance with Recommendation\ Q.320. .sp 1P .LP D.5 \fIDecadic pulsing\fR .sp 9p .RT .PP The decadic pulsing represents the numeric value of each digit by the number of on\(hyhook intervals in a train of pulses. .RT .PP D.5.1 The general characteristics of decadic pulsing are shown below: .sp 9p .RT .LP \fIEquipment\fR \fIPulsing Speed\ (PPS)\fR \fIPercent\ Break\ (BK)\fR .LP Customer\ Dial \ 8\(hy11\ PPS 58\(hy64\ BK .LP 10\(hyPPS\ PBX 10\ \(+-\ 0.3\ PPS 62\(hy66\ BK .LP Sender\ Pulsing 10\ \(+-\ 1\ PPS 57\(hy64\ BK .sp 1P .LP D.6 \fIMulti\(hyfrequency pushbutton\fR .sp 9p .RT .PP See Recommendations Q.11, Q.23 and Q.24. Signal combinations A\(hyD are not usually used in North American private switched networks. .RT .ce 1000 ANNEX\ E .ce 0 .ce 1000 (to Recommendation Q.8) .sp 9p .RT .ce 0 .ce 1000 \fBThe\fR \fBstandard European signalling system for leased\fR .sp 1P .RT .ce 0 .ce 1000 \fBcircuits connecting subscribers to remote PABXs\fR .ce 0 .ce 1000 \fBand public exchanges\fR .ce 0 .LP E.1 \fIIntroduction\fR .sp 1P .RT .PP Recognizing the increasing use of leased lines for interconnection of telephone instruments and public exchanges or private automatic branch exchanges (PABXs) in the European telecommunication networks, a specification has been developed covering the need for signalling on such lines. The system emerged is called Signalling System\ L2. Distinction is made between line signalling (call supervisory signals) and interregister signalling (set\(hyup including routing and additional service control). Taking into account different applications, existing interregister signalling techniques have been adopted for use with the basic line signalling as follows: .RT .LP \(em decadic pulsing (DP); .LP \(em multi\(hyfrequency pushbutton (MFPB) type signalling. .bp .sp 1P .LP E.2 \fIPrinciples and fields of application\fR \v'3p' .sp 9p .RT .PP E.2.1 The line signalling system is to provide supervisory signals (e.g.\ loop signalling in one direction and ringing in the other) between a telephone instrument or its equivalent and a public exchange or PABX in different countries, via an extra long line. .PP E.2.2 For the purpose of description, this specification refers to an instrument signalling unit (ISU) and an exchange signalling unit (ESU). .PP E.2.3 The system is intended for use over four\(hywire circuits but, as an option for national use, it may be used over two\(hywire circuits. In the four\(hywire case, forward and backward signals are segregated by utilizing the four\(hywire circuit as two separate signalling paths. .PP E.2.4 The system is a single voice frequency (1 vf) line signalling system using a signalling frequency of: .LP \(em 2280 Hz in both directions on four\(hywire circuits; .LP \(em 2280 Hz in the direction ISU to ESU and 2400 Hz in the direction ESU to ISU on two\(hywire circuits (national). .PP The use of voice frequency signals renders the system suitable for all voice transmission media, except those using speech interpolation. .PP E.2.5 In addition to the application or removal of signalling frequency (tone\(hyon and tone\(hyoff) in continuous form, the transmission of pulses of signalling frequency is applied. .sp 9p .RT .PP E.2.6 When in the idle condition, the signalling frequency applied to the line by the ISU is reduced in power level to conform to the transmission loading requirements of Recommendation\ Q.15. .PP E.2.7 In accordance with Recommendation Q.25, sending and receiving line splitting arrangements are provided so that signals are contained within the ISU\(hyESU link and not allowed to spill over into the next link. .PP E.2.8 When making an outgoing call, a through speech path shall be provided in the direction ESU\(hyISU prior to the answered state. .PP E.2.9 Signals may be passed in the direction ISU to ESU while speech or audible indications are being received in the direction ESU to ISU. .sp 1P .LP E.3 \fILine signal conditions and signalling codes\fR \v'3p' .sp 9p .RT .PP E.3.1 The line signal conditions and the signalling codes shall be as shown in Tables\ E\(hy1/Q.8 and\ E\(hy2/Q.8. Signal sending and detection requirements are given in \(sc\(sc\ E.3.2 and\ E.3.3. .ce \fBH.T. [T2.8]\fR .ce TABLE\ E\(hy1/Q.8 .ce \fBCalls originated by the telephone instrument\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(60p) | cw(84p) | cw(84p) . Signal Conditions from ISU Conditions from ESU _ .T& lw(60p) | lw(84p) | lw(84p) . Idle Continuous tone\(hyon Continuous tone\(hyoff .T& lw(60p) | lw(84p) | lw(84p) . Seizing Continuous tone\(hyoff Continuous tone\(hyoff .T& lw(60p) | lw(84p) | lw(84p) . Answer Continuous tone\(hyoff Tone\(hyon pulse .T& lw(60p) | lw(84p) | lw(84p) . Recall Recall tone\(hyon pulse Continuous tone\(hyoff .T& lw(60p) | lw(84p) | lw(84p) . Clear Continuous tone\(hyon Continuous tone\(hyoff _ .TE .nr PS 9 .RT .ad r \fBTable E\(hy1/Q.8 [T2.8], p. 4\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T3.8]\fR .ce TABLE\ E\(hy2/Q.8 .ce \fBCalls from the exchange\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(60p) | cw(84p) | cw(84p) . Signal Conditions from ESU Conditions from ISU _ .T& lw(60p) | lw(84p) | lw(84p) . Idle Continuous tone\(hyoff Continuous tone\(hyon .T& lw(60p) | lw(84p) | lw(84p) . Calling Calling tone\(hyon\(hypulse Continuous tone\(hyon .T& lw(60p) | lw(84p) | lw(84p) . Answer Continuous tone\(hyoff Continuous tone\(hyoff .T& lw(60p) | lw(84p) | lw(84p) . Recall Continuous tone\(hyoff Recall tone\(hyon pulse .T& lw(60p) | lw(84p) | lw(84p) . Clear Continuous tone\(hyoff Continuous tone\(hyon _ .TE .nr PS 9 .RT .ad r \fBTable E\(hy2/Q.8 [T3.8], p. 5\fR .sp 1P .RT .ad b .RT .PP E.3.2 A continuous tone\(hyon condition shall be the application of the signalling frequency to the send signalling path for a period exceeding 350\ ms. A tone\(hyon pulse signal shall be the application of the signalling frequency to the send signalling path for a period of 45\(hy135\ ms or 210\(hy240\ ms (see \(sc\ E.5.2). .sp 9p .RT .PP A continuous tone\(hyoff condition shall exist when any signalling frequency is absent from the send signalling path for a period exceeding 80\ ms. .PP E.3.3 A tone\(hyon condition applied to the receive signalling path line termination may be recognized as a continuous tone\(hyon condition for signalling, when it has persisted for 250\ ms, while for a tone\(hyoff condition a value of 40\ ms has to be taken into account. .sp 9p .RT .PP A tone\(hyon condition applied to the receive signalling path line termination, and persisting for a period of 35\(hy150\ ms or 200\(hy250\ ms (see\ \(sc\ E.5.2) may be recognized as a tone\(hyon pulse signal. .sp 2P .LP E.4 \fILine signalling transmission requirements\fR .sp 1P .RT .sp 1P .LP E.4.1 \fISignal sender\fR \v'3p' .sp 9p .RT .PP E.4.1.1 The signalling tone shall be at a frequency of 2280 (2400 Hz in the ESU for two\(hywire working) \(+- | \ Hz. .PP E.4.1.2 The tone\(hyon condition shall have two power levels: a high level and a low level. .PP A high level tone shall be sent for the duration of the signal or for a minimum of 300\ ms (whichever is shorter), and for a maximum of 550\ ms after which it must be reduced to low level. .LP a) A high level tone\(hyon condition shall be a signalling tone transmitted at a level of \(em10\ dBm0\ \(+- | \ dB. .LP b) A low level tone\(hyon condition shall be a signalling tone transmitted at a level of \(em20\ dBm0\ \(+- | \ dB. .sp 1P .LP E.4.2 \fISignal receiver\fR \v'3p' .sp 9p .RT .PP E.4.2.1 A frequency within the range 2280 (2400 Hz in the ISU for two\(hywire working) \(+- | 5\ Hz at an absolute level\ \fIN\fR , within the range (\(em30\ +\ \fIn\fR \ \(=\ \fIN\fR \ \(=\ \(em4\ +\ \fIn\fR )\ dBm shall be recognized as a tone\(hyon condition; where\ \fIn\fR \ is the relative power level at the receive signalling path line termination (see Recommendation\ G.171). .PP E.4.2.2 Any frequency or combination of frequencies having a total absolute power level of less than (\(em40\ +\ \fIn\fR )\ dBm shall be recognized as a tone\(hyoff condition; where\ \fIn\fR is the relative power level at the receive signalling path line termination as in\ \(sc\ E.4.2.1. .bp .sp 1P .LP E.5 \fIGeneral line signal transfer procedures\fR \v'3p' .sp 9p .RT .PP E.5.1 The calling signal is a series of tone\(hyon pulses with a duration of each pulse according to the length of the original ringing pulse and in step with the period of the ringing signal. .PP E.5.2 As an option and subject to mutual agreement by the parties involved, the ISU applies a recall signal in the form of a tone\(hyon pulse to the signalling path. .PP The length of tone\(hyon pulse applied by the ISU depends upon the type of recall employed by the associated telephone, e.g.\ timed break or earthed loop. .PP E.5.3 As an option and subject to mutual agreement by the parties involved, the answer signal is sent by the ESU. .sp 1P .LP E.6 \fIDecadic pulsing\fR .sp 9p .RT .PP For decadic pulsing interregister signalling, the 2280 Hz line signalling is used. Some characteristics are given below. .RT .PP E.6.1 The break periods of decadic pulses shall be applied to the send signalling path of the ISU, as pulses of tone\(hyon condition within the following limits. .sp 9p .RT .LP SPEED\ (pulses\ per\ sec.) .LP BREAK\ PULSE | | 11 12 .LP MIN MAX MIN MAX MIN MAX MIN MAX .LP DURATION\ (ms) .LP 45 112 45 81 45 61 45 52 .PP E.6.2 Pulses of tone\(hyon condition applied to the receive signalling path line termination of the ESU, consistent with the following speed and duration limits, are break periods of dial pulses (address signal). .sp 9p .RT .LP SPEED\ (pulses\ per\ sec.) .LP BREAK\ PULSE | | 11 12 .LP MIN MAX MIN MAX MIN MAX MIN MAX .LP DURATION\ (ms) .LP 35 122 35 91 35 71 35 62 .LP .rs .sp 20P .LP \fBMONTAGE:\ \fR REC.\ Q.9 A LA FIN DE CETTE PAGE .sp 1P .RT .LP .bp