.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\ II
\v'4P'
.RT
.ce 0
.sp 1P
.ce 1000
\fBSUPPLEMENTS\ TO\ SERIES\ M\ AND\ N\ RECOMMENDATIONS\fR \v'2P'
.EF '%	 \ \ \ ^''
.OF ''' \ \ \ ^	%'
.ce 0
.sp 1P
.LP
.rs
.sp 30P
.ad r
Blanc
.EF '%	 \ \ \ ^''
.OF ''' \ \ \ ^	%'
.ad b
.RT
.LP
.bp
.LP
\fBMONTAGE:\fR PAGE 94 = PAGE BLANCHE
.sp 1P
.RT
.LP
.bp
.IP
\fB1\ Technical information\fR 	\v'6p'
.sp 1P
.RT
.sp 2P
.LP
\fBSupplement\ No.\ 1.1\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBPREFIXES\ USED\ IN\ THE\ DECIMAL\ SYSTEM\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.1''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.1	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 409, Volume IV.2 of
the \fIGreen Book\fR )
\v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 1.2\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBTRANSMISSION\ MEASUREMENT\ CONVERSION\ TABLES\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.2''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.2	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 409, Volume IV.2
of the \fIGreen Book)\fR \v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 1.3\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBTHE\ NORMAL\ (OR\ LAPLACE\(hyGAUSS)\ DISTRIBUTION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.3''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.3	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 416, Volume IV.2
of the \fIGreen Book\fR )
\v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 1.4\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMETHODS\ OF\ QUALITY\ CONTROL\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.4''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.4	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 422, Volume IV.2
of the \fIGreen Book\fR )
\v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 1.5\fR 
.RT
.sp 2P
.ce 1000
\fBMATHEMATICAL\ PROCESSING\ OF\ THE\ MEASUREMENT\ RESULTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.5''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.5	%'
.ce 0
.sp 1P
.ce 1000
\fBOF\ THE\ VARIATIONS\ OF\ THE\ OVERALL\ LOSS\ OF\ TELEPHONE\ CIRCUITS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 451, Volume IV.2
of the \fIGreen Book\fR )
\v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 1.6\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBSTATISTICAL\ THEORY\ REQUIREMENTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.6''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 1.6	%'
.ce 0
.sp 1P
.LP
(For this Supplement, see page 459, Volume IV.2 of
the \fIGreen Book\fR )
.bp
.sp 9p
.RT
.sp 1P
.ce 1000
.ce 0
.sp 1P
.IP
\fB2\ Measuring techniques\fR 	
.sp 1P
.RT
.sp 2P
.LP
\fBSupplement\ No.\ 2.1\fR 
.RT
.sp 2P
.ce 1000
\fBSOME\ GENERAL\ OBSERVATIONS\ CONCERNING\ MEASURING\ INSTRUMENTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.1''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.1	%'
.ce 0
.sp 1P
.ce 1000
\fBAND\ MEASURING\ TECHNIQUES\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 463, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.2\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMEASUREMENTS\ OF\ LOSS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.2''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.2	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 471, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.3\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBLEVEL\ MEASUREMENTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.3''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.3	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 475, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.4\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMEASUREMENT\ OF\ CROSSTALK\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.4''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.4	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 480, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.5\fR 
.RT
.sp 2P
.ce 1000
\fBMEASURING\ ERRORS\ AND\ DIFFERENCES\ DUE\ TO\ IMPEDANCE\ INACCURACIES\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.5''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.5	%'
.ce 0
.sp 1P
.ce 1000
\fBOF\ INSTRUMENTS\ AND\ APPARATUS.\ USE\ OF\ DECOUPLED\ MEASURING\ POINTS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 482, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.6\fR 
.RT
.sp 2P
.ce 1000
\fBERRORS\ IN\ THE\ INDICATIONS\ GIVEN\ BY\ LEVEL\(hyMEASURING\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.6''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.6	%'
.ce 0
.sp 1P
.ce 1000
\fBINSTRUMENTS\ DUE\ TO\ INTERFERING\ SIGNALS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 489, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.7\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMEASUREMENT\ OF\ GROUP\ DELAY\ AND\ GROUP\(hyDELAY\ DISTORTION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.7''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.7	%'
.ce 0
.sp 1P
.LP
(For this Supplement, see page 492, Volume IV.2 of
the \fIGreen Book\fR )
.bp
.sp 9p
.RT
.sp 1P
.ce 1000
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.8\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMEASUREMENTS\ OF\ SUDDEN\ PHASE\ CHANGES\ ON\ CIRCUITS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.8''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.8	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 508, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.9\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBVIBRATION\ TESTING\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.9''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.9	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 511, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.10\fR 
.RT
.sp 2P
.ce 1000
\fBMETHOD\ FOR\ MEASURING\ THE\ FREQUENCY\ SHIFT\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.10''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.10	%'
.ce 0
.sp 1P
.ce 1000
\fBINTRODUCED\ BY\ A\ CARRIER\ CHANNEL\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 522, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.11\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBRAPID\ VERIFICATION\ TEST\ FOR\ ECHO\ CONTROL\ DEVICES\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.11''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.11	%'
.ce 0
.sp 1P
.PP
Recommendation M.580 discusses the setting\(hyup and lining\(hyup of
international circuits for public telephony. This Supplement describes 
a method for the rapid verification of adequate echo control on those circuits 
fitted 
with echo control devices when they are initially established.
.sp 1P
.RT
.PP
\fB1\fR This test should be performed after all loss and noise testing 
of a newly established circuit is completed. It consists of an exchange 
of tones to verify that the echo control device at each terminal is functional 
as wired in the circuit. 
.sp 9p
.RT
.PP
\fB2\fR The circuit control should initiate the test with the distant
international maintenance centre. It is intended to be applied during initial 
line\(hyup to every circuit (manual and automatic) with a control device 
at each terminal should there be any doubt that echo control is not effective 
for 
either end.
.sp 9p
.RT
.PP
\fB3\fR If we label the calling maintenance centre the A Terminal, and 
the called maintenance centre the B\ Terminal, the following sequential 
procedure 
should be applied as indicated, and then also with\ A and\ B interchanged.
.sp 9p
.RT
.PP
3.1
Terminal A sends a 1020 Hz
.FS
For additional information
concerning the choice of a test frequency, see Recommendation\ O.6\ [1]
.FE
tone at \(em15\ dBm0 to Terminal\ B.
.PP
3.2
Terminal B sends a 1020 Hz tone at \(em21 dBm0 to Terminal A after
the 1020\ Hz tone is heard at\ B.
.PP
3.3
No 1020 Hz tone should be heard at Terminal A. \fIOn the contrary\fR , 
if a tone is heard, echo control at Terminal\ B is not taking place. The 
echo 
control device at\ B should be checked as appropriate to the type of device 
in the circuit. 
.bp
.PP
3.4
Remove the 1020 Hz tone at Terminal A to cause the release of the echo 
control device at Terminal\ B. 
.PP
3.5
The 1020 Hz tone from Terminal B should be heard at Terminal\ A to verify 
that the B\ control device has released. \fIOn the contrary\fR , if tone 
is 
not heard, check the echo control device\ B.
.PP
3.6
Remove all 1020 Hz test tones from Terminal\ A and Terminal\ B. The above 
test is simply a check to determine that the echo control device is 
effectively in the circuit at each terminal. \fIIt is not a substitute for\fR 
\fIdetailed echo control device testing\fR .
.sp 2P
.LP
	\fBReference\fR 
.sp 1P
.RT
.LP
[1]
	CCITT Recommendation \fI1020 Hz reference test frequency\fR , Vol.\ IV,
Rec.\ O.6.
.sp 2P
.LP
\fBSupplement\ No.\ 2.12\fR 
.RT
.sp 2P
.ce 1000
\fBAN\ AUTOMATIC\ DATA\ ACQUISITION\ AND\ EFFECTIVE\ PROCESSING\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.12''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.12	%'
.ce 0
.sp 1P
.ce 1000
\fBPROCEDURE\ FOR\ GROUP\ AND\ SUPERGROUP\ PILOT\ LEVELS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 524, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.13\fR 
.RT
.sp 2P
.ce 1000
\fBLOOP\ METHOD\ FOR\ THE\ MAINTENANCE\ OF\ 4\(hyWIRE\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.13''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.13	%'
.ce 0
.sp 1P
.ce 1000
\fBTELEPHONE\(hyTYPE\ LEASED\ CIRCUITS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 267, Volume IV.1
of the \fIOrange Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.14\fR 
.RT
.sp 2P
.ce 1000
\fBAUTOMATIC\ MEASURING\ DEVICE\ FOR\ CARRIER\ SYSTEMS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.14''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.14	%'
.ce 0
.sp 1P
.ce 1000
\fBWITH\ A\ LARGE\ NUMBER\ OF\ CHANNELS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 268, Volume IV.1
of the \fIOrange Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.15\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBDETECTION\ OF\ CIRCUIT\ FAULTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.15''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.15	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 275, Volume IV.1
of the \fIOrange Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 2.16\fR 
.RT
.sp 2P
.ce 1000
\fBRECEIVING\ RELATIVE\ LEVELS\ AT\ RENTERS'\ PREMISES\ FOR\ INTERNATIONAL\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.16''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.16	%'
.ce 0
.sp 1P
.ce 1000
\fB\fBLEASED\ CIRCUITS\ USED\ FOR\ DATA\ TRANSMISSION\fR 
.FS
This   Supplement is based upon the replies received to the
questionnaire appearing in CCITT\ Collective
letter\ No.\ 17 (11 June 1981). A detailed analysis of the replies appears 
in Contribution COM IV\(hyNo. 46 of 
the 1981\(hy1984\ Study\ Period.
.FE
.ce 0
.sp 1P
.LP
\fB1\fR 	\fBGeneral\fR 
.sp 1P
.RT
.PP
In the Series\ M Recommendations dealing with special quality
international leased circuits (Recommendations\ M.1020\ [1] and M.1025\ 
[2]), it is advised that the receiving relative level at the renters' premises 
should 
not be lower than \(em13\ dBr. This is a minimum value, and assumes that 
the power of the transmitted data signal is the maximum allowed by 
Recommendation\ V.2\ [3], namely \(em13\ dBm0.
.bp
.PP
Under the above conditions, the absolute power available to the line signal 
detector of the receiving data modem is \(em26\ dBm\ \(em\ the minimum 
value 
required by some modems specified in Series\ V\ Recommendations.
.PP
The value of \(em13\ dBr makes no allowance for present and foreseen
influences on the received absolute power at data modems, as discussed
below.
.RT
.sp 2P
.LP
\fB2\fR 	\fBInfluences on the absolute power received at renters' premises\fR 
.sp 1P
.RT
.sp 1P
.LP
2.1
	\fIGeneral\fR 
.sp 9p
.RT
.PP
The value of absolute power received at a renter's premises (and
therefore available to a modem) is influenced by a number of factors, as
follows:
.RT
.LP
	\(em
	power of the data signal transmitted by the sending modem;
.LP
	\(em
	variations of overall loss with time on the international
leased circuit;
.LP
	\(em
	effect of loss/frequency distortion on the international
leased circuit;
.LP
	\(em
	errors in circuit engineering and line\(hyup.
.PP
Each of these influences is discussed below.
.sp 1P
.LP
2.2
	\fITransmitted power\fR 
.sp 9p
.RT
.PP
The majority of Administrations have adopted the maximum data
signal power level permitted by Recommendation\ V.2 [3], namely, \(em13\ dBm0.
However, a significant number of Administrations already use a level of
\(em15\ dBm0, while others intend to use this level in the future.
.RT
.sp 1P
.LP
2.3
	\fIVariations of overall loss with time\fR 
.sp 9p
.RT
.PP
The overall loss of an international leased circuit is permitted to vary 
between \(+- | \ dB of the nominal value; see, for example, 
Recommendation\ M.1020\ [1], \(sc\ 2.4.
.PP
In the international network and many national networks, extensive use 
is made of automatic gain control equipment on FDM groups, supergroups, 
etc. 
and on transmission systems. Also, improved circuit engineering and an
expanding international network have led to circuits having relatively 
simple constitutions. Finally, international leased circuits benefit from 
the inherent gain stability of digital transmission media, which are increasingly 
being used in their provision. 
.PP
The net effect of the above factors is that the expected variation in overall 
loss of an international leased circuit is much lower than \(+- | \ dB, 
and may be negligible in most cases. 
.RT
.sp 1P
.LP
2.4
	\fILoss/frequency distortion\fR 
.sp 9p
.RT
.PP
The loss/frequency distortion of an international leased circuit is determined 
with respect to the loss at 1020\ Hz. However, the centre of the 
frequency band produced by Series\ V data modems is in the range 1700\ Hz to
1800\ Hz.
.PP
Where a circuit has required equalization for loss/frequency
distortion, the difference between the loss at 1020\ Hz and that at 1700/1800\ 
Hz is negligibly small. But, where a circuit does not have required equalization, 
this difference can be significant. Typical values are 1\ dB for circuits 
to 
Recommendation\ M.1020\ [1], and 5\ dB for circuits to
Recommendation\ M.1025\ [2].
.RT
.sp 1P
.LP
2.5
	\fIErrors in circuit engineering or line\(hyup\fR 
.sp 9p
.RT
.PP
Any error in the engineering or line\(hyup of an international leased circuit 
which increases/decreases its nominal overall loss will obviously have 
a direct and proportional impact on the absolute power received at the 
renter's premises. 
.RT
.sp 2P
.LP
\fB3\fR 	\fBImpact on the receiving relative level at renters' premises\fR 
.sp 1P
.RT
.PP
Each of the factors discussed in \(sc\ 2 will have a calculable impact 
upon the absolute power received at a renter's premises. This impact is 
likely to differ for different Administrations and will depend upon such 
influences as the size of the national network, the extent to which automatic 
gain control is used and the relations with which the Administration operates 
circuits. 
.bp
.PP
Thus, individual Administrations must determine what impact, if any, the 
factors in \(sc\ 2 have upon the receiving relative level they must adopt 
(have adopted) to ensure proper modem operation. 
.RT
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	 CCITT Recommendation \fICharacteristics of special quality international\fR 
\fIleased circuits with special bandwidth conditioning\fR , Vol.\ IV, Rec.\ 
M.1020. 
.LP
[2]
	 CCITT Recommendation \fICharacteristics of special quality international\fR 
\fIleased circuits with basic bandwidth conditioning\fR , Vol.\ IV, Rec.\ 
M.1025. 
.LP
[3]
	 CCITT Recommendation \fIPower levels for data transmission over telephone\fR 
\fIlines\fR , Vol.\ VIII, Rec.\ V.2. 
.sp 2P
.LP
\fBSupplement\ No.\ 2.17\fR 
.RT
.sp 2P
.ce 1000
\fBRESULTS\ OF\ AN\ INVESTIGATION\ OF\ THE\ \fR \fBSERVICE\ AVAILABILITY\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.17''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 2.17	%'
.ce 0
.sp 1P
.ce 1000
\fBPERFORMANCE\ OF\ INTERNATIONAL\ LEASED\ CIRCUITS\fR \fB\ MADE\ IN\ 1982\fR 
.ce 0
.sp 1P
.LP
\fR \fB1\fR 	\fBIntroduction\fR 
.sp 1P
.RT
.PP
Using the assessment procedure specified in
Recommendation\ M.1016\ [1], 13\ Administrations participated in an investigation 
of the service availability performance of their mutual international leased 
circuits. This investigation was undertaken from 1\ January\ 1982
(0000 UTC
.FS
UTC\ =\ Coordinated universal time (UTC equals GMT, but replaces
it).
.FE
) to 31\ March\ 1982 (2400 UTC), and involved 910 full\(hytime,
point\(hyto\(hypoint international leased circuits.
.PP
This supplement contains the results of this investigation, as
evaluated by the Federal Republic of Germany.
.RT
.sp 2P
.LP
\fB2\fR 	\fBResults\fR 
.sp 1P
.RT
.PP
2.1
Table\ 1 gives the general performance results for all (910)
international leased circuits involved. The results under column\ B are 
based on faults and down\(hytimes known to the control stations (Recommendation\ 
M.1012\ [2]) of the circuits. The results under column\ C are based on 
information from the sub\(hycontrol stations (Recommendation\ M.1013\ [3]) 
\fIand\fR the control 
stations.
.sp 9p
.RT
.PP
2.2
Table\ 2 gives the service availability performance results for
each Administration involved in the investigation. For each case, only those
international leased circuits to the remaining 12\ Administrations participating 
in the investigation are included. 
.PP
2.3
The cumulative frequency distribution graph in Figure\ 1 shows the percentage 
of circuits (\fIy\fR \(hyaxis) and the corresponding downtime (\fIx\fR 
\(hyaxis) 
recorded during the observation period. The key results (from Table\ 1,
column\ B) have been shown on the graph.
.PP
2.4
In accordance with the procedures specified in
Recommendation\ M.1016\ [1] (\(sc\ 5.2 and Annex\ C), the Administrations
participating in the performance assessment also exchanged additional
information for consideration when results from different sources are
compared.
.PP
The results of the analysis of this information appear in Table\ 3. Again, 
column\ B relates to information from the control stations while column\ 
C is based on information from both control and sub\(hycontrol stations. 
.PP
2.5
It must be emphasized that all the results in Tables\ 1 and\ 2 and Figure\ 
1 relate to a three\(hymonth observation period, as mentioned in \(sc\ 
1 
above.
.bp
.ce
\fBH.T. [T1.217]\fR 
.ce
TABLE\ 1
.ce
\fBData and service availability performance results for all circuits
.ce
involved in the assessment\fR 
.ce
(Observation period = 3 months)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(72p) .
Information from:
.T&
cw(156p) | cw(36p) | cw(36p) .
Data and results  (A)	Control station  (B)	 {
Control and sub\(hycontrol
stations
(C)
 }
.TE
.TS
lw(148p) | lw(8p) | lw(36p) | lw(36p) .
 {
\ 910
\ \  | 10
b)
Number of faults on all circuits
 }			
.T&
lw(148p) | lw(8p) | lw(36p) | lw(36p) .
 {
1357
\ 2 | 49
c)
Downtime of all circuits
(h)
8819
11 | 50
d)
Mean downtime per circuit
(h)
\ \ \ 9.7
\ \ \  | 2.8
e)
Mean time to restore service (MTRS)
(h)
\ \ \ 6.5
\ \ \ \  | .7
f)
Mean number of faults per circuit
 }			
.T&
lw(148p) | lw(8p) | lw(36p) | lw(36p) .
\ \ \ 1.49
\ \ \ \  | .25
g)
Mean availability per circuit
(%)
\ \ 99.55
\ \ \  | 9.40
h)
Mean time to failure (MTTF)
(h)
1443
\ \  | 54
i)
Circuits with downtime better than mean value
(%)
\ \ 80.0
j)
Circuits for which no downtime was recorded
(%) 
\ \ 47.7
k)
Downtime not exceeded by 95% of the circuits
(h) 
\ \ 54.0
.TE
.LP
\fINote\fR
\ \(em\ A later investigation held in 1983 on 22 circuits showed results
which are in line with the above results.
.RT
.ad r
\fBTable 1 [T1.217], p. 1\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 29
.bp
.ce
\fBH.T. [T2.217]\fR 
.ce
TABLE\ 2
.ce
\fBResults from each country to all other countries\fR 
.ce
\fBInvestigation of international leased circuits\fR 
.ce
(Observation period = 3 months)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(18p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(18p) | lw(16p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(16p) .
											
.T&
lw(18p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(18p) | lw(16p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(16p) .
		(hours) (hours) (hours) 	(%) (hours) (%) (%) (hours)								
.T&
lw(18p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(18p) | lw(16p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(16p) .
 {
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
 }											
_
.T&
lw(18p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(18p) | lw(16p) | lw(18p) | lw(18p) | lw(22p) | lw(22p) | lw(16p) .
											
.TE
.nr PS 9
.RT
.ad r
\fBTable 2 [T2.217], p. 2\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 6
.bp
.LP
.rs
.sp 32P
.ad r
\fBFigure\ 1, p. 3\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T3.217]\fR 
.ce
TABLE\ 3
.ce
\fBResults of analysis of additional information exchanged between the
.ce
participating Administrations\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(156p) | cw(36p) sw(36p) , ^  | c | l.
Replies (% of circuits)	Control station only  (B)
	 {
Control and sub\(hycontrol stations
(C)
 }	
_
.T&
lw(156p) | lw(36p) | lw(36p) .
		
.TE
.nr PS 9
.RT
.ad r
\fBTable 3 [T3.217], p. 4\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	CCITT Recommendation \fIAssessment of the service availability\fR 
\fIperformance of international leased circuits\fR , Vol.\ IV. Rec.\ 1016.
.LP
[2]
	 CCITT Recommendation \fICircuit control station for leased and special\fR 
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1012. 
.LP
[3]
	CCITT Recommendation \fISub\(hycontrol station for leased and special\fR 
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1013.
.LP
[4]
	 CCITT Recommendation \fICharacteristics of ordinary quality international\fR 
\fIleased circuits\fR , Vol.\ IV, Rec.\ M.1040. 
.LP
[5]
	 CCITT Recommendation \fICharacteristics of special quality international\fR 
\fIleased circuits with special bandwidth conditioning\fR , Vol.\ IV, 
Rec.\ M.1020.
.LP
[6]
	 CCITT Recommendation \fICharacteristics of special quality international\fR 
\fIleased circuits with basic bandwidth conditioning\fR , Vol.\ IV, 
Rec.\ M.1025.
.bp
.IP
\fB3\ Supplements to the Series O Recommendations\fR 	
.sp 1P
.RT
.sp 1P
.ce 1000
(see Fascicle IV.4)
.sp 9p
.RT
.ce 0
.sp 1P
.IP
\fB4\ Transmission performance of the international network\fR 	
.sp 1P
.RT
.sp 2P
.LP
\fBSupplement\ No.\ 4.1\fR 
.RT
.sp 2P
.ce 1000
\fBSTABILITY\ OF\ OVERALL\ LOSS\ AND\ PSOPHOMETRIC\ NOISE:\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.1''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.1	%'
.ce 0
.ce 1000
\fBRESULTS\ OF\ ROUTINE\ MAINTENANCE\ MEASUREMENTS\fR 
.ce 0
.ce 1000
\fBMADE\ ON\ THE\ INTERNATIONAL\ NETWORK\fR 
.ce 0
.sp 1P
.ce 1000
\fBDURING\ THE\ FIRST\ HALF\ OF\ 1978\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 68 of Fascicle\ IV.3 of the \fIYellow Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.2\fR 
.RT
.sp 2P
.ce 1000
\fBRESULTS\ AND\ ANALYSIS\ OF\ THE\ 10th\ SERIES\ OF\ TESTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.2''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.2	%'
.ce 0
.sp 1P
.ce 1000
\fBOF\ SHORT\ BREAKS\ IN\ TRANSMISSION\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 80 of Fascicle IV.3 of the \fIYellow Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.3\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBCHARACTERISTICS\ OF\ LEASED\ INTERNATIONAL\ TELEPHONE\(hyTYPE\ CIRCUITS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.3''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.3	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 564, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.5\fR 
.RT
.sp 2P
.ce 1000
\fBINSTRUCTIONS\ FOR\ MAKING\ FUTURE\ MEASUREMENTS\ OF\ THE\ TRANSMISSION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.5''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.5	%'
.ce 0
.ce 1000
\fBQUALITY\ OF\ COMPLETE\ CONNECTIONS\ FOR\ RECORDING\fR 
.ce 0
.sp 1P
.ce 1000
\fBTHE\ RESULTS\ OF\ THE\ MEASUREMENTS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 569, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.6\fR 
.RT
.sp 2P
.ce 1000
\fBINSTRUCTIONS\ FOR\ MAKING\ FUTURE\ MEASUREMENTS\ OF\ THE\ TRANSMISSION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.6''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.6	%'
.ce 0
.ce 1000
\fBQUALITY\ OF\ NATIONAL\ EXTENSIONS\ (EXCLUDING\ SUBSCRIBER'S\ LOCAL\ LINES)
.ce 0
.sp 1P
.ce 1000
\fBAND\ FOR\ RECORDING\ THE\ RESULTS\ OF\ THE\ MEASUREMENTS\fR 
.ce 0
.sp 1P
.LP
(For this Supplement, see page 580,
Volume IV.2 of the \fIGreen Book\fR )
.bp
.sp 9p
.RT
.sp 1P
.ce 1000
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.7\fR 
.RT
.sp 2P
.ce 1000
\fBINSTRUCTIONS\ FOR\ MAKING\ FUTURE\ MEASUREMENTS\ OF\ THE\ TRANSMISSION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.7''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.7	%'
.ce 0
.ce 1000
\fBQUALITY\ OF\ INTERNATIONAL\ CIRCUITS\ AND\ INTERNATIONAL\ CENTRES\ AND\fR 
.ce 0
.sp 1P
.ce 1000
\fBFOR\ RECORDING\ THE\ RESULTS\ OF\ THE\ MEASUREMENTS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 587, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.8\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBRESULTS\ AND\ ANALYSIS\ OF\ TESTS\ OF\ IMPULSIVE\ NOISE\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.8''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.8	%'
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 593, Volume IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.9\fR 
.RT
.sp 2P
.ce 1000
\fBWEIGHTING\ OF\ MEASUREMENTS\ RELATING\ TO\ THE\ STABILITY\ OF\ CIRCUITS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.9''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.9	%'
.ce 0
.ce 1000
\fBIN\ THE\ INTERNATIONAL\ NETWORK\ ACCORDING\ TO\ THE\ SIZE\fR 
.ce 0
.sp 1P
.ce 1000
\fBOF\ CIRCUIT\ GROUPS\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 283, Volume IV.1
of the \fIOrange Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 4.10\fR 
.RT
.sp 2P
.ce 1000
\fBTRANSIENT\ ANALOGUE\ CIRCUIT\ IMPAIRMENTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.10''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 4.10	%'
.ce 0
.sp 1P
.ce 1000
\fBAND\ THEIR\ EFFECT\ ON\ DATA\ TRANSMISSION\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 86 of Fascicle IV.3 of the \fIYellow Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.IP
\fB5\ Maintenance of television circuits\fR 	
.sp 1P
.RT
.sp 2P
.LP
\fBSupplement\ No.\ 5.1\fR 
.RT
.sp 2P
.ce 1000
\fBREQUIREMENTS\ FOR\ THE\ TRANSMISSION\ OF\ TELEVISION\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 5.1''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 5.1	%'
.ce 0
.sp 1P
.ce 1000
\fBSIGNALS\ OVER\ LONG\ DISTANCES\fR 
.ce 0
.sp 1P
.ce 1000
(For this Supplement, see page 598 of Fascicle\ IV.2 of the \fIGreen Book\fR )
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 5.2\fR 
.RT
.sp 2P
.ce 1000
\fBSETTING\(hyUP\ AND\ TESTING\ OF\ INTERNATIONAL\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 5.2''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 5.2	%'
.ce 0
.sp 1P
.ce 1000
\fBVIDEOCONFERENCE\ STUDIOS\fR 
.ce 0
.sp 1P
.ce 1000
(Information submitted by the United Kingdom)
.sp 9p
.RT
.ce 0
.sp 1P
.PP
\fB1\fR To ensure the adequate performance of international digital
videoconference calls it is necessary to check, before any videoconference
studio is put into international service, compatibility with existing studios 
and that minimum technical standards are achieved. 
.bp
.sp 1P
.RT
.PP
The standards for establishing a videoconference studio are given  in\ [1].
.PP
Having established a new videoconference studio to these standards it is 
then necessary to make checks of the satisfactory performance between the 
new studio and an established (reference) studio. These checks are described 
in the following sections. 
.RT
.sp 2P
.LP
\fB2\fR 	\fBTest equipment\fR 
.sp 1P
.RT
.PP
To conduct the tests it will be necessary to have the following
test equipment:
.RT
.LP
	a)
	a white noise generator set to a bandwidth of 50 Hz\(hy10\ kHz;
.LP
	b)
	a filter which produces a flat (within 3\ dB) white or pink
noise response within the band 250\(hy3000\ Hz rolling off at
48\ dB/octave outside these limits;
.LP
	c)
	an audio amplifier and associated loudspeaker with the
following properties:
.LP
	i)
	the loudspeaker must be able to deliver a sound
pressure level of at least 100\ dB SPL
.FS
SPL = sound
pressure level
.FE
at 150\ mm from the loudspeaker in
the axis of the loudspeaker;
.LP
	ii)
	the acoustic properties must be similar to the
average human mouth (as regards the law of decreasing
acoustic pressure in the axis of emission and the law of
directivity);
.LP
	iii)
	the loudspeaker must be single and small (diameter
less than 15\ cm) conforming to DIN\ 45 | 00;
.LP
	d)
	a sound pressure level meter (with A\(hyweighting and linear
scale);
.LP
	e)
	a level measuring set.
.sp 2P
.LP
\fB3\fR 	\fBVideo tests\fR 
.sp 1P
.RT
.PP
3.1
Electronically generated colour bars should be viewed on video
monitors both locally, and at the distant end, from each camera in turn 
and any noticeable degradation should be corrected. 
.sp 9p
.RT
.PP
3.2
Each camera should be checked in turn for correct colour balance and saturation. 
Cameras with remote pan, zoom or focus options should also have those tested. 
.PP
3.3
Satisfactory pictures of the distant studio should be subjectively judged 
on the local studio monitor. 
.PP
3.4
Camera switching should also be tested. Switching should not cause excessive 
break\(hyup of picture. Composite syncs should be in synchronisation and 
colour subcarriers should be in phase for all video sources. 
.PP
3.5
Facilities such as graphics, split screen, slides, facsimile,\ etc, should 
be tested to ensure correct operation. (When testing the graphics 
option, it is important to ensure that the codec has been switched to its 
high resolution mode.) 
.sp 2P
.LP
\fB4\fR 	\fBAudio tests\fR 
.sp 1P
.RT
.PP
The audio tests described in \(sc\ 4.2 shall be performed after the
studio has been set up in accordance 
with \(sc\ 4.1.
.PP
The audio levels should be set up using a white noise source. The
position of microphones should not be changed throughout the tests and 
should represent their location during actual calls. 
.PP
It should be noted that the levels specified for the following tests are 
based on those given in\ [1] but modified by experience. 
.RT
.sp 1P
.LP
4.1
	\fILocal audio test\fR \v'3p'
.sp 9p
.RT
.LP
	i)
	Connect the white noise generator, filter, amplifier and
loudspeaker in series. With the Sound Pressure Level Meter
(SPLM) placed as in Figure\ 1,\ a), adjust the white noise level
to measure 90\ dBSPL on the SPLM.
.bp
.LP
	ii)
	The loudspeaker should now be positioned relative to the
optical reference point (ORP \(em see Note) as in Figure\ 1b) and the audio
levels at the input to the codec should have an average value of \(em9\ 
dBm with 
respect to all seating positions.  Any adjustment to achieve this should be
made immediately prior to the codec (Figure\ 1,\ b)).
.LP
	\fINote\fR \ \(em\ The optical reference point is the point located 1200\ mm
from the floor level and 150\ mm to the rear of the working edge of the
conference desk and on the centre line of each seating position.
.LP
	iii)
	The white noise generator, filter and amplifier should be
used to simulate the nominal received level (\(em9\ dBm) from a codec into the
studio loudspeaker. Measure the sound pressure level at the ORP which should 
be in the range of 67\ to 75\ dBA, depending on the acoustic conditions 
(Figure\ 1,\ c)).
.PP
The audio level at the input to the codec due to
loudspeaker/microphone acoustic coupling should be measured at less than
\(em40\ dBm.
.LP
.rs
.sp 37P
.ad r
\fBFigure 1, p. 5\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.2
	\fIAudio tests (studio\(hyto\(hystudio)\fR  | Figure 2)
.sp 9p
.RT
.PP
In the following tests, each end will be required to send and
measure audio levels at the codec interface. For ease of testing each end 
has been designated either\ A or\ B and this should be decided prior to 
any testing. 
.PP
The received level at \*QA\*U will be referred to as studio Level\ 1 and
the received level at \*QB\*U will be referred to as studio Level\ 2.
.RT
.LP
.rs
.sp 9P
.ad r
\fBFigure 2, p. 6\fR 
.sp 1P
.RT
.ad b
.RT
.PP
The white noise source referred to below is positioned as in
Figure\ 1,\ b) and adjusted as described 
in \(sc\ 4.1\ ii).
.LP
	\(em
	\fIElectrical noise\fR 
.LP
	Conditions:
	A and B mute room microphones.
.LP
	A and B enable echo canceller.
.LP
	Measurements:
	Level 1 = electrical noise from Studio\ B.
.LP
	Level 2 = electrical noise from Studio\ A.
.LP
	Specification:
	Level 2 < \(em53 dBm (flat) at audio output
of codec.
.LP
	Level 1 < \(em53 dBm (flat) at audio output
of codec.
.sp 1P
.LP
4.2.1
	\fI\*QA\*U end audio tests\fR 
.sp 9p
.RT
.LP
	a)
	\fILevel check\fR 
.LP
	Conditions:
	B sends white noise source at \(em9\ dBm level.
.LP
	B enables studio microphone.
.LP
	A mutes studio microphone.
.LP
	A and B enable echo cancellers.
.LP
	Measurements:
	i)
	A measures Level 1 at audio output
of codec.
.LP
	ii)
	A measures sound pressure level at
ORP.
.LP
	Specification:
	i)
	Level 1 at audio output of
codec = \(em9\ dBm.
.LP
	ii)
	Level at ORP = 67 to 75 dBA.
.LP
	b)
	\fIEcho check\fR 
.LP
	Conditions:
	A sends white noise at \(em9 dBm level.
.LP
	B enables studio microphones.
.LP
	A and B enable echo cancellers.
.LP
	Measurements:
	A measures Level 1 (echo).
.LP
	Specification:
	Level 1 < \(em40 dBm at audio output of
codec.
.LP
	c)
	\fIEcho return loss measurement\fR 
.LP
	Conditions:
	A sends white noise at \(em9 dBm level.
.LP
	B enables studio microphones.
.LP
	A enables echo canceller.
.LP
	B disables echo canceller.
.LP
	Measurements:
	A measures Level 1.
.LP
	Specification:
	Level 1 < \(em15 dBm at audio output of
codec.
.LP
	d)
	\fICrosstalk check\fR 
.LP
	Conditions:
	A sends white noise at \(em9 dBm level.
.LP
	B mutes studio microphones.
.LP
	A and B enable echo canceller.
.LP
	Measurements:
	A measures level 1 (crosstalk).
.LP
	Specification:
	Level 1 < \(em50 dBm.
.bp
.sp 1P
.LP
4.2.2
	\fI\*QB\*U end audio tests\fR 
.sp 9p
.RT
.LP
	a)
	\fILevel check\fR 
.LP
	Conditions:
	A sends white noise source at \(em9 dBm level.
.LP
	A enables source microphone.
.LP
	B mutes studio microphone.
.LP
	B and A enable echo cancellers.
.LP
	Measurements:
	i)
	B measures Level 1 at audio output
of codec.
.LP
	ii)
	B measures sound pressure level at
ORP.
.LP
	Specification:
	i)
	Level 2 at audio output of
codec = \(em9\ dBm.
.LP
	ii)
	Level at ORP = 67 to 75\ dBA.
.LP
	b)
	\fIEcho check\fR 
.LP
	Conditions:
	B sends white noise a \(em9 dBm level.
.LP
	A enables studio microphones.
.LP
	B and A enable echo cancellers.
.LP
	Measurements:
	B measures Level 1 (echo).
.LP
	Specification:
	Level 2 < \(em40 dBm at audio output of
codec.
.LP
	c)
	\fIEcho return loss measurement\fR 
.LP
	Conditions:
	B sends white noise at \(em9\ dBm level.
.LP
	A enables studio microphones.
.LP
	B enables echo canceller.
.LP
	A disables echo canceller.
.LP
	Measurements:
	B measures Level 2.
.LP
	Specification:
	Level 2 < \(em15 dBm at audio output of
codec.
.LP
	d)
	Crosstalk check
.LP
	Conditions:
	B sends white noise at \(em9 dBm level.
.LP
	A mutes studio microphones.
.LP
	B and A enable echo canceller.
.LP
	Measurements:
	B measures Level 2 (crosstalk).
.LP
	Specification:
	Level 2 < \(em50 dBm.
.sp 2P
.LP
\fB5\fR 	\fBOverall subjective checks\fR 
.sp 1P
.RT
.PP
As a final confidence check, the general quality of the sound and vision 
received from the distant studio should be subjectively checked at the 
\*QA\*U and\ \*QB\*U ends for all seating positions. 
.RT
.sp 2P
.LP
	\fBReference\fR 
.sp 1P
.RT
.LP
[1]
	CEPT T/TR 01\(hy02E (Nice, 1985)
.IP
\fB6\ Miscellaneous\fR 	
.sp 1P
.RT
.sp 2P
.LP
\fBSupplement\ No.\ 6.1\fR 
.RT
.sp 2P
.ce 1000
\fBEFFECT\ ON\ MAINTENANCE\ OF\ THE\ INTRODUCTION\ OF\ NEW\ COMPONENTS\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 6.1''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 6.1	%'
.ce 0
.sp 1P
.ce 1000
\fBAND\ OF\ MODERN\ EQUIPMENT\ DESIGN\fR 
.ce 0
.sp 1P
.LP
(For this Supplement, see page 620,
Volume IV.2 of the \fIGreen Book\fR )
.bp
.sp 9p
.RT
.sp 1P
.ce 1000
.ce 0
.sp 1P
.sp 2P
.LP
\fBSupplement\ No.\ 6.2\fR 
.RT
.sp 2P
.ce 1000
\fBNEW\ OPERATION\ AND\ MAINTENANCE\ ORGANIZATION\ IN\ THE\ MILAN\ ITALCABLE\fR 
.EF '%	Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 6.2''
.OF '''Fascicle\ IV.3\ \(em\ Suppl.\ No.\ 6.2	%'
.ce 0
.sp 1P
.ce 1000
\fBINTERCONTINENTAL\ TELECOMMUNICATIONS\ CENTRE\fR 
.ce 0
.sp 1P
.ce 1000
(Information submitted by Italcable)
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR 	\fBIntroduction\fR 
.sp 1P
.RT
.PP
The purpose of this Supplement is to inform the readers of
Volume\ IV about the new operation and maintenance organization which began
service in\ 1986 in the Milan Italcable Intercontinental Telecommunications
Centre.
.PP
The organization which has been implemented consists essentially in
the integration of the transmission, line signalling and switching technical
staff into one single group.
.PP
The motivation behind these changes is that at the Italcable Centre
the type of switching equipment is completely electronic, equipment rooms of
the Centre are grouped in a logistical arrangement and the digitalization
process within the Centre is at an advanced stage.
.PP
This situation has given Italcable the opportunity to change its
organization to exploit the advantages offered by a purely digital
network.
.RT
.sp 2P
.LP
\fB2\fR 	\fBLogistical arrangement of equipment rooms\fR \v'3p'
.sp 1P
.RT
.LP
	\(em
	The transmission and switching systems are on the same
floor.
.LP
\fR 	\(em
	The supervision room is the same for the transmission and
switching equipment and is placed in an intermediate position
between the rooms where the transmission and switching systems
are located.
.LP
	\(em
	The supervision of both transmission and switching systems
from the same technical staff allows integrated control of the
the telephone system and faster elimination of failures.
.sp 2P
.LP
\fB3\fR 	\fBDigitalization process\fR 
.sp 1P
.RT
.PP
In Italy, as in other countries, the process of digitalization of the transmission 
and switching equipment is in the phase of gradual 
implementation.
.PP
Particularly in the Milan Italcable Intercontinental Centre a digital switching 
system is in the phase of testing (at present 2\ SPC wholly electronic 
exchanges of the type TDM/PAM are active). 
.PP
The switching exchanges in Italy with which the Milan Italcable
Centre is connected are also replacing their electromechanical switches with
digital ones.
.RT
.sp 2P
.LP
\fB4\fR 	\fBTechnicians training\fR 
.sp 1P
.RT
.PP
The most onerous problem that Italcable had to overcome was
re\(hytraining the technical staff by means of courses and the organization of
periods of cooperative work in order to obtain a homogeneous and thorough
preparation of technicians with different knowledge and background experience.
.PP
To guarantee the operation and the maintenance of the transmission and 
switching equipment, Italcable had to provide the same course twice for 
two 
separate groups, in order that a group of qualified technicians was always
available for service.
.PP
This principle was attained both for the switching technicians who
attended a transmission course and for the transmission technicians who
attended a switching course.
.PP
A period of side\(hyby\(hyside collaboration followed the theoretical
training in order to obtain the experience required.
.PP
The whole training phase lasted about 10\ months for a total of
35\ man\(hymonths.
.bp
.RT
.sp 2P
.LP
\fB5\fR 	\fBOrganization\fR 
.sp 1P
.RT
.PP
Italcable has now an organization for the transmission and the
switching equipment which is subdivided into 4\ sections, namely:
.RT
.LP
	1)
	planning,
.LP
	2)
	operation,
.LP
	3)
	hardware maintenance,
.LP
	4)
	software maintenance.
.PP
Only the staff of the Operation Section, which is employed for
maintaining the continuity of service, is present 24\ hours a day, seven\ 
days a week. 
.PP
The other technicians work normal office hours five\ days a week. This 
has allowed in the Milan Centre an easy transition towards an organization, 
which has now been carried out, based on a division according to
functions.
.RT
.sp 2P
.LP
\fB6\fR 	\fBConclusions\fR 
.sp 1P
.RT
.PP
After about a year of experience with the new organization, it is possible 
to estimate with some certainty the advantages reached in the Milan 
Intercontinental Centre to which about 3000\ circuits are connected (about\ 
1200 are international): 
.RT
.LP
	1)
	The centralized supervision of the transmission and
switching equipment has eliminated the wasted periods of time
which were needed for the transmission of failure information
between transmission and switching staff. It has also allowed
a global view of the telephone communication process and,
consequently, it has reduced the duration of \*Qout\(hyof\(hyservice
periods\*U.
.LP
	2)
	The integration of the switching and transmission functions
has improved the efficiency of the staff and it has increased
the operational efficiency (+16% improvement in number of
operated circuits/man\(hyhours worked monthly).
.LP
	3)
	As a whole there has been an improvement, both in quality
of service and availability of the transmission and switching
systems.
.LP
	4)
	Concerning the changes involved for the operation staff, it
is evident that this has become less problematic and overall
more efficient.
.LP
.rs
.sp 23P
.ad r
Blanc
.ad b
.RT
.LP
.bp