.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
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.ds CF
.EQ
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.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'
.LP
\fBMONTAGE: FIN DE LA RECOMMANDATION R.102 EN\(hyT\* | TE DE CETTE PAGE\fR 
.sp 2P
.LP
\v'16P'
\fBRecommendation\ R.103\fR 
.RT
.sp 2P
.ce 1000
\fBCODE\ AND\ SPEED\(hyDEPENDANT\ TDM\ 600\ BIT/S\ SYSTEM\ FOR\ USE\ IN\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.103''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.103	%'
.ce 0
.sp 1P
.ce 1000
\fBPOINT\(hyTO\(hyPOINT\ OR\ BRANCH\(hyLINE\ MULDEX\ CONFIGURATIONS\fR 
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a) 
that telex subscribers are often geographically located in small groups;
.PP
(b) 
that TDM multiplexing systems are economical for the
transmission of large numbers of channels;
.PP
(c) 
that certain telex switches handle TDM frames in
accordance with Series\(hyR Recommendations directly and that frame fill 
should be optimized; 
.PP
(d) 
that telex switches handle channels at 50 bauds and a
7.5\ unit code;
.PP
(e) 
that a facility for regenerating start\(hystop signals is
used in new TELEX networks;
.PP
(f
)
that the branch\(hyline multiplexing system should be
capable of accepting and regenerating all the signals of the TELEX signalling 
system; 
.PP
(g)
that the minimum signal transfer delay through TDM systems is achieved 
by the transmission of interleaved elements, 
.sp 1P
.LP
\fIrecommends\fR 
.sp 9p
.RT
.PP
that, where banch\(hyline remote or low multiplex capacity TDM
systems are to be used for telegraphy, the equipment shall comply with the
following standards:
.sp 2P
.LP
\fB1\fR 	\fBSystem capacity\fR 
.sp 1P
.RT
.PP
The system shall be capable of multiplexing up to 8 channels at
50\ bauds (7.5\ bits including a stop element of 1.5\ units).
.RT
.sp 2P
.LP
\fB2\fR 	\fBStart\(hystop channel inputs\fR 
.sp 1P
.RT
.PP
2.1
The modulation rate tolerance that shall be accepted on incoming 50\ baud 
start\(hystop signals with a stop element of 1.4\ units shall be at least 
\(+- | .4%. 
.sp 9p
.RT
.PP
2.2
\fR When receiving characters at 50 bauds having nominally 1.5\(hyunit 
stop elements, the system shall be capable of transmitting without error 
isolated incoming characters that have a 1\(hyunit stop element, occurring at a
maximum rate of one per second.
.bp
.PP
2.3
The minimum interval between start elements of undistorted
successive continuous characters that may be presented at the channel input
when the nominal modulation rate is 50\ bauds shall be 145\ 5/6\ ms.
.PP
2.4
\fR There shall be no restriction on the continuous transmission of all 
characters (including combination No.\ 32 of International Telegraph 
Alphabet No.\ 2) when they are presented at the maximum permitted rate.
.PP
2.5
The effective net margin on all channel inputs when undistorted
signals are received from a transmitter having a nominal character length 
and rate shall be at least 40%. 
.PP
2.6
At the nominal modulation rate of 50 bauds, an input character
start element shall be rejected if it is less than 0.4\ units duration 
and shall be accepted if it is more than 0.6\ units duration. 
.PP
2.7
Elements corresponding to start polarity (at the distant
multiplexer output) shall be inserted in the aggregate stream if the channels 
are unequipped. 
.PP
2.8
In the case of an open\(hycircuit line condition at the start\(hystop
channel input, it shall be possible to choose to transmit elements
corresponding to a steady start or stop polarity in the aggregate bit stream, 
according to the availability polarity selected. 
.sp 2P
.LP
\fB3\fR 	\fBStart\(hystop channel outputs\fR 
.sp 1P
.RT
.PP
3.1
The maximum degree of gross start\(hystop distortion, produced by the system 
on a start\(hystop channel, shall be 3% for all modulation rates. 
.sp 9p
.RT
.PP
3.2
The maximum difference possible between the mean modulation rate of the 
channel output signals and the nominal modulation rate shall be 0.2%. 
.PP
3.3
The minimum stop element duration released at the ouptut shall be 1.25\ 
units, whatever the distortion, the length of the stop element or the 
input rate within the range specified in \(sc\(sc\ 2.1 to\ 2.4 of this 
Recommendation of the character recognized at the other end, whether this 
character is in 
accordance with this Recommendation of Recommendations\ R.101, R.102 or\ R.112
(for a rate of 50\ bauds and a 7.5\ unit code).
.PP
3.4
Within 6 ms of the recognition of one of the failures described in \(sc\(sc\ 
8.3 and\ 8.4 or carrier loss signalled by the modem, the steady polarity 
as selected in accordance with \(sc\ 2.8 shall be applied to the channel 
outputs of 
the \fITDM system affected\fR .
.PP
3.5
The affected terminal shall signal its synchronization status to the distant 
terminal over the signalling channel provided (control channel). 
.sp 2P
.LP
\fB4\fR 	\fBMultiplexing details\fR 
.sp 1P
.RT
.PP
4.1
Channel interleaving shall be on a \fIbit\(hyby\(hybit multiplexing\fR 
\fIbasis\fR .
.sp 9p
.RT
.PP
4.2
Both start and stop elements of each input character shall be
transmitted through the aggregate.
.PP
4.3
The transfer delay shall not exceed 60 ms.
.sp 2P
.LP
\fB5\fR 	\fBFrame structure\fR 
.sp 1P
.RT
.PP
5.1
A unique frame of 12 bits, of duration 20 ms, equivalent to an
aggregate signal rate of 600\ bit/s shall be used, as shown in Table\ 1/R.103:
.sp 9p
.RT
.PP
5.2
The frame may be considered as a 600 bit/s \fIstart/stop\fR character, 
time slot \*Q12\*U being the start element of polarity\ A, slots\ 10 and\ 
11 forming the stop element of polarity\ Z, as shown in Figure\ 1/R.103. 
.sp 2P
.LP
\fB6\fR 	\fBAggregate signal details\fR 
.sp 1P
.RT
.PP
6.1
The aggregate signal rate shall be 600\ bit/s. The tolerance on the modulation 
rate of the receive aggregate signals of the TDM system shall be 
between\ +2.3% and\ \(em0.5%.
.sp 9p
.RT
.PP
6.2
The effective net margin of the aggregate signal receiver of the TDM system 
shall be at least 40%. 
.PP
6.3
The maximum degree of isochronous distortion of the send aggregate signals 
of the TDM system shall 
be\ 5%.
.bp
.ce
\fBH.T. [T1.103]\fR 
.ce
TABLE\ 1/R.103
.ce
\fBFrame details\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(60p) .
Remote muldex slot	Use
_
.T&
cw(60p) | cw(60p) .
\ 1	Data channel 1
.T&
cw(60p) | cw(60p) .
\ 2	Data channel 2
.T&
cw(60p) | cw(60p) .
\ 3	Data channel 3
.T&
cw(60p) | cw(60p) .
\ 4	Data channel 4
.T&
cw(60p) | cw(60p) .
\ 5	Data channel 5
.T&
cw(60p) | cw(60p) .
\ 6	Data channel 6
.T&
cw(60p) | cw(60p) .
\ 7	Data channel 7
.T&
cw(60p) | cw(60p) .
\ 8	Data channel 8
.T&
cw(60p) | cw(60p) .
\ 9	Control channel
.T&
cw(60p) | cw(60p) .
10	Z synchronization
.T&
cw(60p) | cw(60p) .
11	Z synchronization
.T&
cw(60p) | cw(60p) .
12	A synchronization
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/R.103 [T1.103], p. 1\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure 1/R.103, p. 2\fR 
.sp 1P
.RT
.ad b
.RT
.PP
6.4
When the TDM system is operated over an international
telephone\(hytype circuit, a modem complying with the appropriate aspects 
of the Series\(hyV Recommendations (in particular Recommendation\ V.23) 
should preferably be employed. 
.sp 2P
.LP
\fB7\fR 	\fBControl channel encoding\fR 
.sp 1P
.RT
.PP
7.1
The 50 bit/s control channel, the position of which in the frame described 
in\ 5 is accurately known, enables all risk of imitation to be 
eliminated.
.sp 9p
.RT
.PP
7.2
The structure of the control channel shall be in accordance with Figure\ 
2/R.103. It corresponds to an anisochronous character with a recurrence 
of 240\ ms, formed from a one unit start element of polarity\ Z, five information 
elements and a six unit stop element of polarity\ A. 
.bp
.LP
.rs
.sp 11P
.ad r
\fBFigure 2/R.103, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
7.3
The control channel information provides for the transmission of information 
in accordance with Table\ 2/R.103. 
.ce
\fBH.T. [T2.103]\fR 
.ce
TABLE\ 2/R.103
.ce
\fBInformation transmitted by the control channel\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | lw(102p) .
5	4	3	2	1	Information elements Function
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(102p) .
0	0	0	0	0	 {
Without alarm or other informations (default)
 }
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(102p) .
0	0	1	0	0	Loss of synchronism
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(102p) .
0	0	0	0	1	 {
Loop \*Qd\*U request
(Remoteloop 2 on 600\ bit/s aggregate)
 }
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(102p) .
1	X	X	X	X	National use
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
0	1	0	0	0	 {
Remoteloop \*Qf\*U on TG channel\ 1
 }	0	1
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
0	0	1	2	0	1	0	1
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
0	3	0	1	0	1	1	4
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
0	1	1	0	0	5	0	1
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
1	0	1	6	0	1	1	1
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(66p) | cw(18p) .
0	7	0	1	1	1	1	8
.TE
.LP
\fINote\fR
\ \(em\ The least significant bits are sent first.
.nr PS 9
.RT
.ad r
\fBTableau 2/R.103 [T2.103], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB8\fR 	\fBSynchronizing\fR 
.sp 1P
.RT
.PP
8.1
The maximum average synchronization time in the absence of error and imitation 
shal be 600\ ms. 
.sp 9p
.RT
.PP
8.2
Synchronism shall be considered acheived after recognition of the frame 
positioning pattern (sequence of two elements of polarity\ Z followed by 
an element of polarity\ A) as described in\ 5 and at least two successive 
recognitions of the control channel (6\ elements of polarity\ A followed 
by one element of polarity\ Z modulo\ 12) in compliance witn\ 7. 
.PP
8.3
The maximum time loss of synchronization due to a steady polarity signal 
shall be 120\ ms. 
.PP
8.4
The maximum time loss of synchronization for repeated error on the synchronization 
pattern in the control channel shall be 380\ ms. 
.sp 2P
.LP
\fB9\fR 	\fBTelex signalling\fR 
.sp 1P
.RT
.PP
9.1
Specifications for the signals used to establish, to clear and to control 
telex calls are laid down in Recommendation\ U.1 (types\ A and\ B),\ U.11 
(type\ C) and\ U.12 (type\ D). Recommendation\ U.25 lists the modes of 
both\(hyway 
telex signalling on a single circuit and the signalling combinations on 
a given aggregate that a TDM terminal shall be capable of handling. 
.sp 9p
.RT
.PP
9.2
Recommendation U.25 also lays down the tolerances on the control signals 
from a TDM terminal to telex and vice versa. 
.sp 2P
.LP
\fB10\fR 	\fBMaintenance\fR 
.sp 1P
.RT
.PP
The branch looping facilities shall remain in accordance with
Recommendation\ R.115.
.RT
.sp 2P
.LP
\fB11\fR 	\fBNumbering of channels\fR 
.sp 1P
.RT
.PP
The numbering of channels for the branch line telegraph muldex is given 
in Tables\ 1/R.114 and\ 4/R.114 in accordance with the numbering scheme 
concerning Recommendations\ R.101 and\ R.102.
.RT
.sp 2P
.LP
\fB12\fR 	\fBChannel selection\fR 
.sp 1P
.RT
.PP
Remote channels shall be grouped so as to provide maximum ease of use of 
heterogeneous frames, a time slot allocation involving little variation 
in the sampling rate being retained. 
.PP
The selection of channel grouping and the method used shall be based on 
bilateral agreement, particularly when the channels of an existing system 
have to be branched without there being any possibility of a reconfiguration 
of the whole. 
.PP
Tables 3/R.103 and 4/R.103 give an example of remote channel grouping on 
the basis of muldexes in conformity with Recommendation\ R.101 or\ R.102. 
.RT
.LP
.rs
.sp 16P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T3.103]\fR 
.ce
TABLE\ 3/R.103
.ce
\fBExample of grouping of remote channels for an R.101 muldex\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(36p) | cw(36p) | cw(108p) .
	200 baud channels  eliminated	50 baud channels extended
_
.T&
cw(36p) | cw(36p) | cw(108p) .
Remote channel 1	2001  2004	 {
\ \ \ 0501, 0513, 0525, 0536
 | 504, 0516(2), 0528, 0539
 }
_
.T&
cw(36p) | cw(36p) | cw(108p) .
Remote channel 2	2005  2009	 {
\ \ \ 0505, 0529, 0517, 0540
\ \ \ 0509, 0532, 0521, 0544
 }
_
.T&
cw(36p) | cw(36p) | cw(108p) .
Remote channel 3	2002  2006	 {
\ \ \ 0502, 0526, 0514, 0537
\ \ \ 0506, 0530, 0518, 0541
 }
_
.T&
cw(36p) | cw(36p) | cw(108p) .
Remote channel 4	2003  2010	 {
\ \ \ 0503, 0527, 0515, 0538
\ \ \ 0501, 0533, 0522, 0545
 }
_
.T&
cw(36p) | cw(36p) | cw(108p) .
Remote channel 5	2007  2011	 {
\ \ \ 0507, 0531, 0519, 0542
\ \ \ 0511, 0534, 0523, 0546
 }
_
.T&
cw(36p) | cw(36p) | cw(108p) .
		 {
0508, 0512, 0520, 0524, 0535,
0543(1)\fB512, 0520, 0524, 0535\fR
 }
.TE
.LP

\fINote\ 1\fR
\ \(em\ Although incomplete, a sixth remote channel could be implemented
with the remaining 50\ baud channels.
.LP
\fINote\ 2\fR
\ \(em\ Channel 0516 may not be remoted when the corresponding TS is used
to transmit the maintenance channel in the R.101 multiplexer.
.nr PS 9
.RT
.ad r
\fBTableau 3/R.103 [T3.103], p. 5\fR 
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T4.103]\fR 
.ce
TABLE\ 4/R.103
.ce
\fBExample of grouping of remote channels for an R.102 muldex\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(36p) | cw(84p) , ^  | c.
 {
Remote
channel
1
\fBchannel\fR
2
 }	200 baud channels eliminated
	2004 and 2016  2012 and 2020
_
.T&
cw(36p) | cw(84p) .
 {
\fBchannel \fR
\ 3
\fBchannel \fR
\ 4
\fB
channel \fR
\ 5
 }	 {
2001 and 2013
2005 and 2017
2009 and 2021
 }
_
.T&
cw(36p) | cw(84p) .
 {
\fBchannel \fR
\ 6
\fBchannel \fR
\ 7
\fB
channel \fR
\ 8
 }	 {
2002 and 2014
2006 and 2018
2010 and 2022
 }
_
.T&
cw(36p) | cw(84p) .
 {
\fBchannel \fR
\ 9
\fBchannel \fR
10
\fB
channel \fR
11
 }	 {
2003 and 2015
2007 and 2019
2011 and 2023
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 4/R.103 [T4.103], p. 6\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ R.105\fR 
.RT
.sp 2P
.ce 1000
\fBDUPLEX\ MULDEX\ CONCENTRATOR\fR \fB,\ CONNECTING\ A\ GROUP\ OF\ GENTEX\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.105''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.105	%'
.ce 0
.ce 1000
\fBAND\ TELEX\ SUBSCRIBERS\ TO\ A\ TELEGRAPH\ EXCHANGE\ BY\ ASSIGNING\fR 
.ce 0
.sp 1P
.ce 1000
\fBVIRTUAL\ CHANNELS\ TO\ TIME\ SLOTS\ OF\ A\ BIT\(hyINTERLEAVED\ TDM\ 
SYSTEM\fR 
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos,\ 1984; amended at Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a) 
that the specifications of code and speed dependent TDM
muldexes are already given in Recommendation\ R.101;
.PP
(b) 
that code and speed dependent TDM muldexes can be
successfully used for connecting a group of gentex and telex subscribers 
to an exchange; 
.PP
(c) 
that a considerable increase in the efficiency of muldex channel utilization 
may be achieved by concentration, i.e.\ allocating time 
slots to subscribers only while they are operating;
.PP
(d) 
that the busy\(hyhour load generated by gentex
and telex subscribers averages from 0.05 to 0.2\ erlang;
.PP
(e) 
that both the virtual and assigned (fixed) telegraph
channels can be set up on the same aggregate channel using the TDM method;
.sp 1P
.LP
\fIunanimously declares the view\fR 
.sp 9p
.RT
.PP
that, when a 
bit\(hyinterleaved TDM system
is used on gentex and telex subscriber lines for concentrating telegraph 
signals by assigning 
virtual channels
to time slots in the 2400\ bit/s aggregate bit stream, the equipment should 
meet the following requirements: 
.sp 2P
.LP
\fB1\fR 	\fBChannel types\fR 
.sp 1P
.RT
.PP
1.1\fR The 
duplex muldex/concentrator
should ensure that
virtual channels are only allocated time slots in the 2400\ bit/s aggregate 
bit stream for the duration of their seizure. 
.sp 9p
.RT
.PP
1.2
The duplex muldex/concentrator should also ensure that
assigned (fixed) channels are permanently allocated specific time slots 
in the 2400\ bit/s aggregate bit stream. 
.PP
1.3
Virtual channels should ensure the connection of gentex and telex subscribers 
operating at 50 bauds and using the International Telegraph 
Alphabet No.\ 2 (ITA2) code who have an average load of 0.05\ to 0.2\ erlang. 
The use of other rates requires further study. 
.PP
1.4
Assigned (fixed) channels should ensure data and telegraph signal transmission 
in compliance with Recommendation\ R.101, alternative\ B. 
.sp 2P
.LP
\fB2\fR 	\fBSystem capacity\fR 
.sp 1P
.RT
.PP
2.1
The duplex muldex/concentrator should ensure the setting\(hyup
of virtual and assigned channels in any combination within the range of the
2400\ bit/s aggregate rate.
.sp 9p
.RT
.PP
2.2
When a system has only virtual channels, the number of connected subscribers 
with an average load of 0.05 to 0.1\ erlang each should not 
exceed\ 256 and with an average load of\ 0.1 to 0.2\ erlang each should not
exceed\ 128. In either case, the percentage value of the failures to connect 
is not more than\ 0.1%. 
.PP
2.3
When a system has only assigned (fixed) channels, their number,
depending on the types and rates of the channels, should comply with
Recommendation\ R.101, alternative\ B.
.bp
.sp 2P
.LP
\fB3\fR 	\fBMultiplexing system specifications\fR 
.sp 1P
.RT
.PP
Multiplexing scheme, frame structure, frame synchronization,
aggregate signal parameters, interfaces, telegraph signal parameters at
input\(hyoutput and telegraph signal delay time should conform to
Recommendation\ R.101, alternative\ B.
.RT
.sp 2P
.LP
\fB4\fR 	\fBVirtual channel\fR \fB parameters\fR 
.sp 1P
.RT
.PP
4.1
Virtual channels are intended for use on the telex network
subscriber section with type\ A and type\ B signalling (Recommendation\ U.1).
.sp 9p
.RT
.PP
4.2
Seizure of virtual channels may be from either end. In order to
decrease the probability of call collisions it is necessary:
.LP
	\(em
	to perform blocking of the backward path immediately after
the first calling signal stop element polarity appearing in a receiver 
vacant channel position; 
.LP
	\(em
	 to establish the following order for seizure of time slots in the opposite 
muldexes; 
.LP
	\(em
	 for a muldex installed at the exchange seizure should start with the 
first in a frame\(hyfree channel time slot while for the opposite muldex 
seizure begins with the last free channel time slot. 
.PP
When encountering a call collision, a through\(hyconnection should be given 
to a call coming from the telegraph exchange, and a busy signal should 
be sent to the calling subscriber. 
.PP
4.3
\fIIn the initial state\fR , a virtual channel should be free and a
start polarity should be transmitted over it between statistical
muldex/concentrator assemblies.
.PP
4.4
\fIWhen a call arrives\fR , i.e. stop polarity with an interval of
more than 150 ms, either from the subscriber side or from the exchange 
side, a virtual channel should be seized, and a stop polarity having a 
duration of 
140\(hy160\ ms should be transmitted over it to the remote side followed by the
transmission of two start\(hystop characters having a length of 8\ units 
each in 
accordance with Figure\ 1/R.105.
.PP
The signal elements indicated as 1 to 8 are used for the
transmission of an 8\(hydigit conventional number indicating which subscriber
(maximum 2\u8\d\ =\ 256; see also \(sc\ 2.2 above) is/should be connected 
to the 
equipment.
.PP
4.5
For error protection of a conventional number, transmitted over a
channel, the following should be carried out:
.LP
	\(em
	a parity check;
.LP
	\(em
	 a check for anticoincidence of a convention number with any of the numbers 
of a circuit already seized. 
.PP
In the case of an error or coincidence of a conventional number a service 
signal (a busy pulse signal or \*QOCC\*U) should be transmitted to the 
connection initiator side (a customer or exchange), returning a customer or
exchange to initial state.
.PP
4.6
The element \*QC\*U of the second start\(hystop character
(see Figure\ 1/R.105) is used for parity check.
.LP
.rs
.sp 12P
.ad r
\fBFigure 1/R.105, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
A parity check element should correspond to the even number of
elements in Z\ condition.
.PP
Element \*QC\*U of the first start\(hystop character remains vacant and 
may be used for service purposes. 
.RT
.PP
4.7
When the setting up of a virtual channel fails because all time slots
are engaged by other virtual or assigned (fixed) channels, a busy signal, 
the structure of which is specified by current CCITT Recommendations should 
be 
returned to the calling subscriber side.
.bp
.sp 2P
.LP
\fBRecommendation\ R.111\fR 
.RT
.sp 2P
.ce 1000
\fBCODE\ AND\ SPEED\ INDEPENDENT\ TDM\ SYSTEM\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.111''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.111	%'
.ce 0
.sp 1P
.ce 1000
\fBFOR\ \fR \fBANISOCHRONOUS\ TELEGRAPH\ AND\ DATA\ TRANSMISSION\fR 
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended at Geneva, 1980 and Malaga\(hyTorremolinos,\ 
1984)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a)
that the use of voice\(hyfrequency telegraph\ (VFT) equipment on voice 
channels provided by frequency division multiplexing of a primary 
group or by time slots in a pulse code modulation\ (PCM) transmission system 
may not always be the optimum solution for telegraph and low\(hyspeed data 
transmission, if aspects of transmission quality, equipment complexity,
technological progress, miniaturization, power consumption and overall 
cost are globally considered; 
.PP
(b)
that the economic transmission of telegraph and low\(hyspeed
anisochronous data signals requiring code\(hy and speed\(hyindependent 
channels may be achieved by using time division techniques; 
.PP
(c)
that a relatively simple TDM (time division multiplex)
system, even if less efficient in bandwidth utilization, might be preferred 
in some (e.g.\ short\(hyhaul) applications; 
.PP
(d)
that Administrations might be interested in conserving code and speed independence 
inherent in VFT systems when replacing them by TDM 
systems;
.PP
(e)
that code and speed independent transmission systems are
capable of transmitting any type of digital signal (anisochronous, isochronous, 
telegraph, data, signalling for switching purposes); 
.PP
(f
)
that a 
code and speed independent TDM system
can adapt its inherent telegraph distortion to the needs of a network,
depending on the number of circuits connected in tandem;
.PP
(g)
that a code and speed independent TDM system can adapt to a number of different 
types of channels (each being defined by its maximum 
modulation rate and inherent distortion);
.PP
(h)
that a basic 64\ kbit/s telegraph multiplexer may provide
interfaces for remote submultiplexers if required. The submultiplexers 
may be associated in some applications with Recommendations\ X.50\ [1] 
and\ X.51\ [2] data multiplexers and with telephone channel modems and/or 
baseband modems; 
.LP
\fIunanimously declares the following views\fR 
.sp 1P
.RT
.sp 2P
.LP
\fB1\fR 	\fB64 kbit/s aggregate\fR 
.sp 1P
.RT
.sp 1P
.LP
1.1
	\fIGeneral\fR 
.sp 9p
.RT
.PP
1.1.1
Where code and speed independent TDM systems for transmission of telegraph 
and low\(hyspeed anisochronous data signals utilize the whole 64\ kbit/s 
capacity (e.g.\ provided by a PCM time slot or a primary group), the equipment 
shall be manufactured to comply with the following standards. 
.sp 9p
.RT
.sp 2P
.LP
1.2
	\fIAggregate bearer channel\fR 
.sp 1P
.RT
.PP
1.2.1 
The aggregate bearer channel may be a 64\ kbit/s PCM\ time
slot or a 64\ kbit/s synchronous data modem in accordance with the
Recommendation cited in\ [3]. The nominal data signalling rate
is 64 | 00\ bit/s with a tolerance of \(+- | \ bit/s.
.bp
.sp 9p
.RT
.sp 2P
.LP
1.3
	\fIFrame structure\fR 
.sp 1P
.RT
.PP
1.3.1
The frame consists of 240\ bits for information plus\ 16
symmetrically distributed service bits for framing and other purposes. The
16th\ bit of the frame is the first service bit. The frame synchronization
pattern comprises the first 12\ service bits in the sequence 101001010101.
.sp 9p
.RT
.PP
1.3.2
The 13th\ service bit is used to inform the opposite multiplexer
terminal of bearer failure as follows: 1\ =\ no bearer failure; 0\ =\ bearer
failure. A minimum of three consecutive\ 0 conditions is the criterion for an
alarm indication.
.PP
1.3.3
The 14th\ service bit is used to inform the opposite multiplexer
terminal of frame alignment loss as follows: 1\ =\ no loss of frame alignment;
0\ =\ frame alignment loss (this may be accompanied by bearer failure). 
A minimum of three consecutive\ 0 conditions is the criterion for an alarm 
indication. 
.PP
1.3.4
The time delay between detection of a bearer failure or frame
alignment loss and the sending of the 0\ condition is for further study.
.PP
1.3.5
The 15th service bit is provisionally fixed to\ 1 and its use is
left for further study.
.PP
1.3.6
The 16th\ service bit (last bit of the frame) may be used for
possible justification and is fixed to\ 1. However, the justification strategy, 
if used, must be agreed bilaterally. 
.PP
1.3.7
The channel numbering scheme is specified in
Recommendation\ R.114.
.sp 2P
.LP
1.4
	\fIType of multiplexing\fR 
.sp 1P
.RT
.PP
1.4.1
Channel interleaving shall be on a bit basis.
.sp 9p
.RT
.PP
1.4.2
The coding method shall be the transition coding process in
accordance with Annex\ A below.
.sp 2P
.LP
1.5
	\fIAllocation of information bits\fR 
.sp 1P
.RT
.PP
1.5.1
The data signalling rate on the bearer for each multiplexed
channel should be 250, 500, 1000, 2000 or 4000\ bit/s corresponding to 
one, two, four, eight or sixteen bits per frame (symmetrically distributed) 
respectively.
.sp 9p
.RT
.PP
1.5.2
The 64\ kbit/s aggregate stream is divided into 60\ kbit/s for
information and 4\ kbit/s for framing and other purposes.
.PP
1.5.3
The 60\ kbit/s information bit stream may be subdivided into five
bit streams of 12\ kbit/s or, for national use or by bilateral agreement, 
into twenty bit streams of 3\ kbit/s. 
.sp 2P
.LP
1.6
	\fITelegraph and data channels\fR 
.sp 1P
.RT
.PP
1.6.1
The nominal modulation rates are 50, 100, 200, 300, 600 and
1200\ bauds. A mixture of these rates should be possible.
.sp 9p
.RT
.PP
1.6.2
The maximum degree of inherent isochronous distortion due to the
sampling process is\ 2.5, 5 or\ 7.5% according to the application as shown in
Table\ 1/R.111, which gives the channel characteristics and full system 
capacity for various telegraph channel rates and for aggregate signalling 
rates of 
64\ kbit/s and below (see \(sc\ 2\ below).
.PP
1.6.3
Where applicable, spurious elements with duration of 1.6\ ms (=\ 8%) or 
less shall be rejected and elements longer than 2\ ms shall be accepted 
at 
the 50\ baud channel input. The element lengths to be rejected or accepted at
higher channel modulation rates is for further study.
.sp 2P
.LP
1.7
	\fIFrame alignment\fR 
.sp 1P
.RT
.PP
1.7.1
Frame realignment is ensured within three correct consecutive
frame synchronization patterns, i.e.\ within\ 12 to\ 16\ ms. In the absence of
frame realignment, the telegraph channel outputs of the demultiplexer should 
be locked in their start polarity state for switched applications. 
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Stop polarity might be required by some Administrations 
on a per channel basis for leased applications. 
.bp
.ce
\fBH.T. [T1.111]\fR 
.ce
TABLE\ 1/R.111
.ce
\fBChannel characteristics and system capacities\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) sw(18p) sw(18p) sw(18p) , ^  | ^  | ^  | ^  | ^  | c | c | c | c.
 {
Nominal
modulation
rate
(bauds)
 }	 {
Maximum degree of isochronous distortion due
to sampling
(%)
 }	 {
Theoretical
maximum
modulation
rate
(bauds)
 }	 {
Data signalling
rate on the
bearer per
channel
(bit/s)
 }	 {
Shortest
isolated
element
(ms)
 }	 {
Maximum number of channels
for an integrated system of
 }
					64  kbit/s	9.6  kbit/s	4.8  kbit/s	2.4  kbit/s
_
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
 {
\ \ 50\fB | fR\(ua\fBa\fR\(ua\fB)\fR
 }	5\fB.5\fR  2.5	\ \ 83  \ 167	\ 250  \ 500	 {
4\fB.25\fR
2\fB.25\fR
 }	240  120	32  16	16  \ 8	8  4
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
 {
\ 100\fB | fR\(ua\fBa\fR\(ua\fB)\fR
 }	5\fB.5\fR  2.5	\ 167  \ 333	\ 500  1000	 {
2\fB.25\fR
1\fB.25\fR
 }	120  \ 60	16  \ 8	\ 8  \ 4	4  2
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
 {
\ 200\fB | fR\(ua\fBa\fR\(ua\fB)\fR
 }	5\fB.5\fR	\ 333	1000	1\fB.25\fR	\ 60	\ 8	\ 4	2
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
 {
\ 300\fB | fR\(ua\fBa\fR\(ua\fB)\fR
 }	7.5	\ 333	1000	1\fB.25\fR	\ 60	\ 8	\ 4	2
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
\ 600 | ua\d\u)\d	7.5	\ 666	2000	0.5\fB2\fR	\ 30	\ 4	\ 2	\(em
.T&
cw(36p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) .
1200 | ua\d\u)\d	7.5	1333	4000	0.25	\ 15	\ 2	\ \(em	\(em
.TE
.LP
\ua\d\u)\d
The number of channels indicated for modulation rates of
600 and 1200 bauds is for information only (homogeneous aggregates at these
rates are not contemplated).
.nr PS 9
.RT
.ad r
\fBTABLE 1/R.111 [T1.111], p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
.sp 3
1.7.2
Three consecutive erroneous frame synchronization patterns should
be regarded as the criterion for loss of frame alignment.
.sp 2P
.LP
1.8
	\fILoss of telegraph input\fR 
.sp 1P
.RT
.PP
1.8.1
In the absence of any signal at a telegraph channel input, the
multiplexer system should reproduce start polarity at the corresponding
output.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Stop polarity might be required by some Administrations 
on a per channel basis for leased applications. 
.sp 2P
.LP
1.9
	\fIBearer interface\fR 
.sp 1P
.RT
.PP
1.9.1
For the interface between the aggregate bearer and a PCM time
slot, either a codirectional or contradirectional 64\ kbit/s interface with
the PCM equipment could be accepted. Even for a codirectional interface no
stuffing device would be provided in the telegraph multiplexer, which would
loop back the 64\ kHz clock.
.sp 9p
.RT
.PP
1.9.2
For the interface to a 64\ kbit/s modem the interchange
circuits of Table\ 2/R.111 should be provided (see the Recommendation cited
in\ [4]).
.sp 2P
.LP
1.10
	\fITelegraph interface\fR 
.sp 1P
.RT
.PP
1.10.1 
The interface between the multiplexer and the telegraph circuits should 
be in accordance with national requirements. 
.bp
.sp 9p
.RT
.ce
\fBH.T. [T2.111]\fR 
.ce
TABLE\ 2/R.111
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(108p) .
 {
Circuit number
(cf. Recommendation\ V.24 | 5])
 }	Function
_
.T&
cw(60p) | lw(108p) .
102 | ua\d\u)\d\fBb\fR	 {
Signal ground or common return
 }
.T&
cw(60p) | lw(108p) .
102b | ub\d\u)\d	DCE common return
.T&
cw(60p) | lw(108p) .
103 | uc\d\u)\d\fBb\fR	Transmitted data
.T&
cw(60p) | lw(108p) .
104 | uc\d\u)\d\fBb\fR	Received data
.T&
cw(60p) | lw(108p) .
 {
109\fBb | fR\(ua\fBb\fR\(ua\fB)\fR
 }	 {
Data channel received line signal detector
 }
.T&
cw(60p) | lw(108p) .
 | 13 | uc\d\u)\d | ud\d\u)\d	 {
Transmitter signal element timing
(DTE source)
 }
.T&
cw(60p) | lw(108p) .
 | 14 | uc\d\u)\d | ud\d\u)\d	 {
Transmitter signal element timing
(DCE source)
 }
.T&
cw(60p) | lw(108p) .
115 | uc\d\u)\d\fBb\fR	 {
Receiver signal element timing
 }
.TE
.LP

\ua\d\u)\d
The provision of this conductor is optional.
.LP
\ub\d\u)\d
This conductor is used in conjunction with interchange
circuit\ 109.
.LP
\uc\d\u)\d
The electrical characteristics of the interchange circuits
marked with a \uc\d\u)\d should be in accordance with
Recommendation\ X.27 | 6]. The circuits not so marked should be
in accord
ance with Recommendation\ X.26 | 7].
.LP
\ud\d\u)\d
Either circuit 113 or 114 is to be used.
.nr PS 9
.RT
.ad r
\fBTable 2/R.111 [T2.111], p. 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.LP
\fB2\fR 	\fBAggregate bearer rates lower than 64\ kbit/s\fR 
.sp 1P
.RT
.sp 2P
.LP
2.1
	\fIGeneral\fR 
.sp 1P
.RT
.PP
2.1.1
Where code and speed independent TDM systems for transmission of telegraph 
and low speed anisochronous data signals make use of capacities 
lower than 64\ kbit/s, the equipment shall be manufactured to comply with the
following standards:
.sp 9p
.RT
.sp 2P
.LP
2.2
	\fIAggregate bearer channels\fR 
.sp 1P
.RT
.PP
2.2.1
Aggregate rates of 2.4, 4.8 and 9.6 kbit/s shall be used. These rates can 
be provided either using modems in accordance with the Series\ V 
Recommendations or using data multiplexers in accordance with
Recommendations\ X.50\ [1] or\ X.51\ [2].
.sp 9p
.RT
.sp 2P
.LP
2.3
	\fIFrame structure\fR 
.sp 1P
.RT
.PP
2.3.1
The frame structure is independent of the frame structure of the 64\ kbit/s 
data multiplexer or of the 64\ kbit/s telegraph multiplexer. However, it 
must be designed to allow easy insertion of the carried telegraph channels 
on to the multiplexer defined in \(sc\ 1\ above (see also \(sc\ 3\ below). 
.bp
.sp 9p
.RT
.PP
2.3.2
For that purpose, one bit out of every six bits will carry
framing information and other functions, which will result in effective 
binary rates of\ 2, 4 or\ 8\ kbit/s with actual aggregate rates of\ 2.4, 
4.8 
and\ 9.6\ kbit/s respectively.
.PP
2.3.3
The frame consists of 160\ information bits plus 32\ symmetrically
distributed service bits for framing and other purposes. The sixth bit 
of the frame is the first service bit. 
.PP
2.3.4
This frame is subdivided into two subframes each consisting of
80\ information bits plus 16\ symmetrically distributed service bits.
.PP
2.3.5
The subframe synchronization pattern comprises the first
12\ service bits in the sequence\ 101001010101.
.PP
2.3.6
For the allocation of the 13th, 14th and 15th service bits,
see \(sc\(sc\ 1.3.2 to 1.3.5\ above. The 16th\ service bit is set at\ 0 
for the first 
subframe and at\ 1 for the second subframe.
.sp 2P
.LP
2.4
	\fIType of multiplexing\fR 
.sp 1P
.RT
.PP
2.4.1
See \(sc\ 1.4\ above.
.sp 9p
.RT
.sp 2P
.LP
2.5
	\fIAllocation of information bits\fR 
.sp 1P
.RT
.PP
2.5.1
The same data signalling rates as defined in \(sc\ 1.5 should be
used (250, 500 and 1000\ bit/s and, where applicable, 2000 and 4000\ bit/s).
.sp 9p
.RT
.PP
2.5.2
Table\ 3/R.111 shows the number of information bits per frame for
the different data signalling rates on the bearer channel. These information
bits are symmetrically distributed among the 160\ information bits of the
frame.
.ce
\fBH.T. [T3.111]\fR 
.ce
TABLE\ 3/R.111
.ce
\fBNumber of information bits per frame\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(78p) | cw(30p) sw(30p) sw(30p) , ^  | c | c | c.
 {
Data signalling rate on the
bearer per channel
(bit/s)
 }	 {
Number of information bits per frame
for each channel in an aggregate system of
 }
	9.6  kbit/s	4.8  kbit/s	2.4  kbit/s
_
.T&
cw(78p) | cw(30p) | cw(30p) | cw(30p) .
\ 250	\ 5	10	20
_
.T&
cw(78p) | cw(30p) | cw(30p) | cw(30p) .
\ 500	10	20	40
_
.T&
cw(78p) | cw(30p) | cw(30p) | cw(30p) .
1000	20	40	80
_
.T&
cw(78p) | cw(30p) | cw(30p) | cw(30p) .
2000	40	80	\(em
_
.T&
cw(78p) | cw(30p) | cw(30p) | cw(30p) .
4000	80	\(em	\(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLE 3/R.111 [T3.111], p. 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
.sp 2
2.6
	\fITelegraph and data channels\fR 
.sp 1P
.RT
.PP
2.6.1
See \(sc\ 1.6\ above.
.bp
.sp 9p
.RT
.sp 2P
.LP
2.7
	\fIFrame alignment\fR 
.sp 1P
.RT
.PP
2.7.1
Frame realignment time is ensured within three correct
consecutive subframe synchronization patterns. This frame realignment will 
be ensured within\ 40, 80 and\ 160\ ms for aggregate rates of\ 9.6, 4.8 
and\ 2.4 kbit/s respectively. In the absence of frame realignment the telegraph 
channel outputs of the demultiplexer should be locked in their start polarity 
state for 
switched applications.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Stop polarity might be required by some Administrations 
on a per channel basis for leased applications. 
.PP
2.7.2
See \(sc\ 1.7.2\ above.
.sp 2P
.LP
2.8
	\fILoss of telegraph input\fR 
.sp 1P
.RT
.PP
2.8.1
See \(sc\ 1.8\ above.
.sp 9p
.RT
.sp 2P
.LP
2.9
	\fIBearer interface\fR 
.sp 1P
.RT
.PP
2.9.1
The interface between the telegraph aggregate and higher
aggregate bearer channels should be as laid down in the relevant
Recommendations for modems and data multiplexers.
.sp 9p
.RT
.sp 2P
.LP
2.10
	\fITelegraph interface\fR 
.sp 1P
.RT
.PP
2.10.1 
See \(sc\ 1.10\ above.
.sp 9p
.RT
.sp 2P
.LP
\fB3\fR 	\fBCompatibility\fR 
.sp 1P
.RT
.PP
3.1
For the different subrates of 2, 4 and 8 kbit/s, there should
be\ 8, 16 and\ 32 information bits respectively distributed symmetrically 
within the 64\ kbit/s aggregate frame. 
.sp 9p
.RT
.PP
3.2
The 160 information bits of the 2.4, 4.8 and 9.6 kbit/s aggregate
rates should correspond to 20\ groups of 8\ bits, 10\ groups of\ 16 and 
5\ groups of 32\ bits respectively. These\ 8, 16 and\ 32 information bits 
should be made to 
correspond to the\ 8, 16 and\ 32\ information bits of the 64\ kbit/s frame 
by means of a special padding/depadding unit. 
.PP
3.3
Some examples of possible implementations are given in
Figures\ 1/R.111, 2/R.111 and\ 3/R.111 for illustration purposes only.
.LP
.rs
.sp 17P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/R.111, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 2/R.111, p. 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 24P
.ad r
\fBFigure 3/R.111, p. 
.sp 1P
.RT
.ad b
.RT
.ce 1000
ANNEX\ A
.ce 0
.sp 1P
.ce 1000
(to Recommendation R.111)
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fBTransition coding process\fR 
.sp 1P
.RT
.ce 0
.LP
.rs
.sp 17P
.ad r
\fBFIGURE A\(hy1/R.111, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
A.1
The sampling pulses are divided into groups of four and each
transition of the anisochronous signal causes a code character of 3\ bits 
to be generated at the rate of one bit for a group of 4\ samples. The first 
T\ bit of this code character indicates the sense of transition while the 
two bits\ C\d1\uand\ C\d2\utranslate into binary code the position of the 
transition in the 
relevant group.
.sp 9p
.RT
.PP
A.2
Following the acceptance of a transition into the coding system, a \*Qdata 
transition lockout condition\*U which inhibits entry of further 
transitions shall persist until code characters T, C\d1\uand C\d2\uhave 
been transmitted. Any transition which has been locked out in this manner 
shall enter the coder as soon as the lockout condition is removed and will 
be coded as if it had occurred in the first quarter of the next transmission 
period.
.sp 9p
.RT
.PP
A.3
The code characters are transmitted over the digital channel at a rate 
of 1\ bit per group of 4\ sampling pulses and the subsequent bits\ P 
between the code characters confirm the polarity of the anisochronous signal 
at the relevant instant. The minimum number of P\ bits may be zero, so 
the maximum code character rate equals 1/3 of the maximum modulation rate 
allowed. 
.sp 9p
.RT
.PP
A.4
When the anisochronous signal has a permanent polarity, an
error of one bit will never entail a continuous inversion of the decoded
signal, but will cause a mutilation of this signal during a limited time. 
The duration of these mutilations is reduced to a minimum when the code 
characters are formed as shown in Table\ A\(hy1/R.111. 
.sp 9p
.RT
.ce
\fBH.T. [T4.111]\fR 
.ce
TABLE\ A\(hy1/R.111
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(18p) sw(18p) sw(18p) | cw(18p) sw(18p) sw(18p) | cw(60p) , c | c | c | c | c | c | ^ .
 {
Code character for a
transition from 1 to 0
in the anisochronous signal
 }	 {
Code character for a
transition from 0 to 1
in the anisochronous signal
 }	 {
Position of the transition
in a group
of four sampling pulses
 }
T	C 1	C 2	T	C 1	C 2
_
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | lw(60p) .
0	0	0	1	1	1	first quarter
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | lw(60p) .
0	0	1	1	1	0	second quarter
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | lw(60p) .
0	1	0	1	0	1	third quarter
.T&
cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | lw(60p) .
0	1	1	1	0	0	fourth quarter
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLE A\(hy1/R.111 [T4.111],  p. 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	 CCITT Recommendation \fIFundamental parameters of a multiplexing scheme\fR 
\fIfor the international interface between synchronous data networks\fR 
, 
Rec.\ X.50.
.LP
[2]
	 CCITT Recommendation \fIFundamental parameters of a multiplexing scheme\fR 
\fIfor the international interface between synchronous data networks using\fR 
\fI10\(hybit envelope structure\fR , Rec.\ X.51.
.LP
[3]
	 CCITT Recommendation \fIModems for synchronous data transmission using\fR 
\fI60\(hy108 kHz group band circuits\fR , Rec.\ V.36, \(sc\ 1 f 
).
.LP
[4]
	\fIIbid.\fR , \(sc\ 10.
.LP
[5]
	CCITT Recommendation \fIList of definitions for interchange circuits\fR 
\fIbetween data terminal equipment and data circuit terminating equipment\fR ,
Rec.\ V.24.
.LP
[6]
	CCITT Recommendation \fIElectrical characteristics for balanced\fR 
\fIdouble\(hycurrent interchange circuits for general use with integrated 
circuit\fR \fIequipment in the field of data communications\fR , Rec.\ 
X.27. 
.LP
[7]
	CCITT Recommendation \fIElectrical characteristics for unbalanced\fR 
\fIdouble\(hycurrent interchange circuits for general use with integrated 
circuit\fR \fIequipment in the field of data communications\fR , Rec.\ 
X.26. 
.bp
.sp 2P
.LP
\fBRecommendation\ R.112\fR 
.RT
.sp 2P
.ce 1000
\fBTDM\ HYBRID\ SYSTEM\fR \fB\ FOR\ ANISOCHRONOUS\ TELEGRAPH\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.112''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.112	%'
.ce 0
.sp 1P
.ce 1000
\fBAND\ DATA\ TRANSMISSION\ USING\ BIT\ INTERLEAVING\fR 
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos,\ 1984; amended at Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a)
that there is a limited requirement on certain routes to provide for rates 
and codes not included in Table\ 1/R.101 which may be achieved by using 
time\(hydivision multiplexing (TDM) techniques; 
.PP
(b)
that wherever possible the rates and codes given in
Table 1/R.101 should not be expanded in the future;
.PP
(c)\fR that Administrations may be asked to provide code and
speed independent channels for cryptography, for telemetry, for rates outside 
the Recommendation\ R.101 tolerance of\ \(+-\ 1.4%, where the rate and 
code may be 
changed frequently, and for maintenance purposes;
.PP
(d)
that the aggregate bit rate may be limited to 2400 bit/s
and TDM equipment may be required to pass code independent and code dependent 
traffic; 
.PP
(e)
that the bearer may not be suitable for using the backward channel as defined 
by 
Recommendation\ V.26, \(sc\ 5\ [1], or in the provision of telegraph channels 
above the Recommendation\ V.26 aggregate by the technique of subdivision 
of the frequency band as given in Recommendation\ H.34\ [2], 
.sp 1P
.LP
\fIunanimously declares the view\fR 
.sp 9p
.RT
.PP
that where bit\(hyinterleaved TDM systems are used for code dependent and 
code independent 
anisochronous telegraph and data transmission
with an aggregate rate of 2400\ bit/s, carried either by analogue telephone\(hytype 
circuit or by higher order TDM system, the equipment should be constructed 
to comply with the following standards: 
.sp 2P
.LP
\fB1\fR 	\fBSystem capacity\fR 
.sp 1P
.RT
.PP
1.1
The TDM system will be capable of multiplexing the rates shown in Table\ 
1/R.101 for code dependent channels to alternative\ B. 
.sp 9p
.RT
.PP
1.2
Each code and rate independent channel should replace three, six or twelve 
50\ baud code dependent channels. 
.PP
1.3
The characteristics of the code independent channels should follow the 
limits shown in Table 1/R.112. 
.ce
\fBH.T. [T1.112]\fR 
.ce
TABLE\ 1/R.112
.ce
\fBCharacteristics of code independent channels\fR 
.ce
\fBand system capacity\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(36p) | lw(42p) | lw(36p) | lw(36p) | lw(36p) | lw(42p) .
					
.T&
lw(36p) | lw(42p) | lw(36p) | lw(36p) | lw(36p) | lw(42p) .
 {
\ 50
8.3
\ 51.06
153.2
6.5\ 
15
100
8.3
102.12
306.4
3.25
\ 7
200
8.3
204.24
612.8
1.625
\ 3
 }					
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/R.112 [T1.112], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB2\fR 	\fBChannel inputs\fR 
.sp 1P
.RT
.PP
2.1
The nominal modulation rate will be 50, 100 or 200 bauds; the
theoretical maximum modulation rate shall be\ 51.06, 102.12 or 204.24\ bauds.
.sp 9p
.RT
.PP
2.2
The transition coding process of telegraph signals is in
accordance with Recommendation\ R.111.
.PP
2.3
Each channel provides its individual coding intervals starting
within the allocated time slots: each coding interval is subdivided into 
four quarters. In that coding interval where the skipping bit occurs in 
the 
subframe, the forth quarter is shortened by one time slot length.
.PP
For a 50 baud channel, transmission of the code character starts with the 
next corresponding time slot. For channels with higher modulation 
rates the transmission of the code characters should be delayed by the 
number of the allocated time slots in the subframe minus\ 3. 
.PP
2.4
Where applicable, spurious elements with duration of 1.6\ ms (=\ 8%) or 
less shall be rejected and elements longer than 2\ ms shall be accepted 
at 
the 50\ baud channel input. The element lengths to be rejected or accepted at
higher channel modulation rates is for further study.
.sp 2P
.LP
\fB3\fR 	\fBChannel outputs\fR 
.sp 1P
.RT
.PP
3.1
The maximum degree of inherent isochronous distortion due to the sampling 
process shall be\ 8.3%. 
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The long\(hyterm system distortion on a tandem connection 
of transition encoded channels of an independent TDM system approximates 
in the 
worst case to the arithmetic summation of the individual link distortions.
.PP
3.2
After a TDM link failure, actions described in \(sc\(sc\ 3.5 and\ 3.6 of 
Recommendation R.101, should be taken on the derived channel output. 
.sp 2P
.LP
\fB4\fR 	\fBMultiplexing details\fR 
.sp 1P
.RT
.PP
4.1
The multiplexing details are in accordance with
Recommendation R.101, alternative B on a bit basis.
.sp 9p
.RT
.PP
4.2
The maximum transfer delay (excluding the modem) for 50, 100 and 200\ baud 
code and rate independent channels for back\(hyto\(hyback terminals shall 
not exceed 50\ ms for the rate 50\ bauds and 35\ ms for rates\ 100 and
200\ bauds. The values of the delay are subject to further study.
.sp 2P
.LP
\fB5\fR 	\fBFrame structure\fR 
.sp 1P
.RT
.PP
This is as defined in Recommendation R.101 alternative B.
.RT
.sp 2P
.LP
\fB6\fR 	\fBSynchronizing\fR 
.sp 1P
.RT
.PP
This is defined in Recommendation R.101, alternative\ B.
.RT
.sp 2P
.LP
\fB7\fR 	\fBAggregate signals and interface, system clock arrangements\fR 
\fBand system control and alarms\fR 
.sp 1P
.RT
.PP
These are defined in Recommendation R.101.
.RT
.sp 2P
.LP
\fB8\fR 	\fBChannel numbering scheme of code independent channels\fR 
.sp 1P
.RT
.PP
Channel numbers used in the given Recommendation represent two last digits 
of the four\(hydigit numbering scheme in respect to the Figure\ 1/R.112, 
first two digits are shown in Recommendation\ R.114.
.bp
.RT
.LP
.rs
.sp 44P
.ad r
\fBFigure 1/R.112, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	CCITT Recommendation \fI2400 bit per second modem standardized\fR 
\fIfor use on 4\(hywire leased telephone\(hytype circuits\fR , Rec.\ V.26.
.LP
[2]
	CCITT Recommendation \fISub\(hydivision of the frequency band of a\fR 
\fItelephone\(hytype circuit between telegraph and other services\fR ,
Rec.\ H.34.
.bp
.sp 2P
.LP
\fBRecommendation\ R.114\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBNUMBERING\ OF\ INTERNATIONAL\ TDM\ CHANNELS\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.114''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.114	%'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a)
that in view of the introduction in the international
service of time division multiplex (TDM) channels with different
characteristics, configured for various nominal modulation rates and for
different character structures, it has become necessary to evolve a method 
of numbering TDM channels; 
.PP
(b)
that this numbering method must make it possible to
recognize:
.LP
	\(em
	the type of TDM (code\(hydependent or code\(hyindependent);
.LP
	\(em
	the nominal modulation rate and (in the case of
code\(hydependent TDM) the character length;
.LP
	\(em
	the position of the channel in the frame,
.sp 2P
.LP
\fIunanimously declares the view\fR 
.sp 1P
.RT
.PP
\fB1\fR 
The channels in an international TDM system conforming to
Recommendation R.101 should be numbered as shown in Table\ 1/R.114.
.sp 9p
.RT
.PP
\fB2\fR 
The number assigned to a channel should be selected from the
series applicable to the type of channel and should correspond to its position 
in the multiplex tables in Recommendation\ R.101. 
.sp 9p
.RT
.PP
\fB3\fR The channels in an international TDM system conforming to
Table\ 1/R.111 should be numbered as shown in Table\ 2/R.114.
.sp 9p
.RT
.PP
\fB4\fR The channels in systems conforming to Table 1/R.111 should be
numbered in the same way as their positions in the frame; i.e.\ in the 
sequence from\ 1 to\ 255 excluding the channel numbers that are multiples 
of\ 16. In 
establishing a channel having a rate of more than 50\ bauds, the number 
assigned coincides with the number of the first 50\ baud channel taking 
part in the 
integration.
.sp 9p
.RT
.PP
\fB5\fR International TDM channels to Recommendation\ R.112 should have 
the numbering scheme shown in Table\ 3/R.114. 
.sp 9p
.RT
.PP
\fB6\fR The numbers assigned to the channels should be selected from the 
series applicable to the type of channel and should correspond to its position 
in the Figure\ 1/R.112 to Recommendation\ R.112. 
.sp 9p
.RT
.PP
\fB7\fR International code independent and code dependent channels to
Recommendation\ R.102 should have the numbering schemes shown in Tables\ 
3/R.114 and\ 4/R.114, respectively. 
.sp 9p
.RT
.PP
\fB8\fR The numbers assigned to the channels should be selected from the 
series applicable to the type of channel and should correspond to its position 
in Tables\ 2/R.102 to\ 4/R.102 to Recommendation\ R.102. 
.sp 9p
.RT
.PP
\fB9\fR Channel numbering of 50 baud channels for branch\(hyline muldexes
conforming to Recommendation\ R.103 should be in accordance with the numbering 
scheme in Tables\ 1/R.114 and\ 4/R.114. 
.sp 9p
.RT
.LP
.rs
.sp 3P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T1.114]\fR 
.ce
TABLE\ 1/R.114
.ce
\fBNumbering scheme for TDM systems conforming\fR 
.ce
\fBto Recommendation R.101\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(60p) | lw(168p) .
	
.T&
lw(60p) | lw(168p) .
 {
\ 50 |  
0501 | (hy | 546
\ 75 |  
0701 | (hy | 742 (for alternative A). See Table 3/R.101
for numbers not used
0701 | (hy | 731 (for alternative B, 0716 not used)
100 |  
1001 | (hy | 023 (for 10 unit, 1008 not used)
1701 | (hy | 723 (for 7\(12 unit, 1708 not used)
110 |  
1101 | (hy | 123 (1108 not used)
134.5
1301 | (hy | 315
150 |  
1501 | (hy | 515
200 |  
2001 | (hy | 011 (for 10 unit, 2008 not used)
2101 | (hy | 111 (for 11 unit, 2108 not used)
2701 | (hy | 711 (for 7\(12 unit, 2708 not used)
300 |  
3001 | (hy | 007 (for 10 unit)
3101 | (hy | 107 (for 11 unit)
 }	
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/R.114 [T1.114], p. 18\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.ce
\fBH.T. [T2.114]\fR 
.ce
TABLE\ 2/R.114
.ce
\fBNumbering scheme for TDM systems\fR 
.ce
\fBconforming to Table 1/R.111\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(48p) | lw(48p) | lw(132p) .
		
.T&
lw(48p) | lw(48p) | lw(132p) .
 {
\ \ 50
\ (300)
5
\ (7.5)
5001 | (hy | 255 (The numbers 16, 32, 48, 64, 80, 96, 112,
128, 144, 160, 176, 192, 208, 224 and 240 are not
used)
\ 100
\ (300)
5
\ (7.5)
6001 | (hy | 127 (The numbers 16, 32, 48, 64, 80, 96 and 112 are
not used)
\ 200\ (300)
5\ (7.5)
7001 | (hy | 063 (The numbers 16, 32 and 48 are not used)
\ 600
\ (300)
7.5
\ (5)
8001 | (hy | 031 (The number 16 is not used)
1200
\ (300)
7.5
\ (5)
8101 | (hy | 115
 }		
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/R.114 [T2.114], p. 19\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T3.114]\fR 
.ce
TABLE\ 3/R.114
.ce
\fBNumbering scheme of code independent channels for TDM\fR 
.ce

.ce
\fBsystems\fR 
.ce
\fBconforming to Recommendations R.112 and R.102\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(66p) | cw(48p) sw(48p) , ^  | ^  | c | c.
 {
Nominal modulation rate
(bauds)
 }	 {
Maximum degree of
isochronous distortion
due to sampling
(%)
 }	Channel numbers
		R.112  (2400 bit/s)	R.102  (4800 bit/s)
_
.T&
cw(30p) | cw(66p) | cw(48p) | cw(48p) .
\ 50	8.3	5801 | (hy | 815	 {
5801 | (hy | 831
(5816 not used)
 }
.T&
cw(30p) | cw(66p) | cw(48p) | cw(48p) .
100	8.3	6801 | (hy | 807	6801 | (hy | 815
.T&
cw(30p) | cw(66p) | cw(48p) | cw(48p) .
200	8.3	7801 | (hy | 803	7801 | (hy | 807
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 3/R.114 [T3.114], p. 20\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 5
.ce
\fBH.T. [T4.114]\fR 
.ce
TABLE\ 4/R.114
.ce
\fBNumbering scheme of code dependent channels for TDM
.ce
\fBsystems\fR 
.ce
\fBconforming to Recommendation\ R.102\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(144p) .
 {
Nominal
modulation rate
(bauds)
 }	Channel numbers
_
.T&
cw(60p) | lw(144p) .
\ 50 |  	0501 | (hy | 592
_
.T&
cw(60p) | lw(144p) .
\ 75 |  	0701 | (hy | 746
_
.T&
cw(60p) | lw(144p) .
100 |  	 {
1001 | (hy | 046 \ \ 
(for 10 unit)
1701 | (hy | 746 \ \ 
(for 7.5 unit)
 }
_
.T&
cw(60p) | lw(144p) .
110 |  	1101 | (hy | 146
_
.T&
cw(60p) | lw(144p) .
134.5	 {
1301 | (hy | 331 \ \ 
(1316 not used)
 }
_
.T&
cw(60p) | lw(144p) .
150 |  	 {
1501 | (hy | 531 \ \ 
(1516 not used)
 }
_
.T&
cw(60p) | lw(144p) .
200 |  	 {
2001 | (hy | 023 \ \ 
(for 10 unit, 2008 not used)
2101 | (hy | 123 \ \ 
(for 11 unit, 2108 not used)
2701 | (hy | 723 \ \ 
(for 7.5 unit, 2708 not used)
 }
_
.T&
cw(60p) | lw(144p) .
300 |  	 {
3001 | (hy | 015 \ \ 
(for 10 unit)
3101 | (hy | 115 \ \ 
(for 11 unit)
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 4/R.114 [T4.114], p. 21\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ R.115\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBMAINTENANCE\ LOOPS\ FOR\ TDM\(hySYSTEMS\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.115''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.115	%'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a)
the increasing use of TDM transmission systems;
.PP
(b)
the volume of information circulating on data and telegraph transmmission 
networks; 
.PP
(c)
the savings to be made by reducing interruption time on
such links;
.PP
(d)
the importance of being able to determine responsibilities between the 
several parties who, of necessity, are involved in maintenance 
questions for the networks;
.PP
(e)
the advantages of standardization regarding maintenance,
.sp 2P
.LP
\fIunanimously declares the following:\fR 
.sp 1P
.RT
.PP
\fB1\fR The locating of faults can be facilitated in many cases by looping
and other maintenance procedures in the TDM equipments. These maintenance
facilities allow local or remote measurements to be carried out optionally 
by the Administrations and/or users concerned. 
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR 	\fBLocation of the loops\fR 
.sp 1P
.RT
.PP
The maintenance loops are positioned in order to make it possible for the 
Administrations to locate faults to the following function 
blocks:
.RT
.LP
	\(em
	aggregate modem;
.LP
	\(em
	TDM central logic;
.LP
	\(em
	tributary interface unit;
.LP
	\(em
	aggregate line;
.LP
	\(em
	subscriber line.
.PP
The loops necessary to fulfil the above listed demands are shown in Figure\ 
1/R.115. Additional loops may be used for the location of faulty 
boards but these loops are relevant to each particular manufacturer's
implementation and are not included here. The number of maintenance loops 
may be extended to include the subscriber terminal equipment. These loops 
are left for further study. 
.sp 2P
.LP
\fB3\fR 	\fBNames, types and definitions of the loops\fR 
.sp 1P
.RT
.PP
See Figure\ 1/R.115.
.RT
.sp 1P
.LP
3.1
	\fILoop\ a\ \(em\ \fR \fIdigital multiplexer aggregate loop\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway or optionally an 
echo\(hyback loop
(see Figures\ 2/R.115 and\ 3/R.115) that shall connect the aggregate data 
output to 
the aggregate data input of the TDM central logic. This loop shall be
accomplished as close as possible to the digital aggregate interface.
.RT
.sp 1P
.LP
3.2
	\fILoop\ b\ \(em\ \fR \fIanalogue aggregate modem loop\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop or optionally an echo\(hyback loop (see
Figures\ 2/R.115 and\ 3/R.115). With this loop, the line signal from the 
output of the aggregate modem is looped back to the input of the aggregate 
modem. The loop should include the maximum number of aggregate modem components 
used in 
normal working.
.bp
.RT
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/R.115, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.3
	\fILoop\ c\ \(em\ \fR \fIanalogue line loop\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop or optionally an echo\(hyback loop (see
Figures\ 2/R.115 and\ 3/R.115). With this loop, the incoming line signal 
at the receiver input of the aggregate modem is looped back to the outgoing 
direction of the line. It is noted that it may not be possible to correctly 
receive data that has been sent over the looped circuit. 
.RT
.sp 1P
.LP
3.4
	\fILoop\ d\ \(em\ \fR \fIdigital aggregate modem loop\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop or optionally an echo\(hyback loop (see
Figures\ 2/R.115 and\ 3/R.115). In this loop the received aggregate digital 
data from the modem is looped back to the originating side. This loop shall 
be 
located as close as possible to the digital aggregate interface.
.RT
.sp 1P
.LP
3.5
	\fILoop\ f\ \(em\ \fR \fItributary analogue loop\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop (see Figure\ 2/R.115). With this loop, the 
tributary signal to be sent to the subscriber is looped back towards the 
multiplex system. This loop shall be accomplished at the subscriber line
interface and shall include as many parts of the tributary interface unit as
possible. As long as the loop is set the subscriber connection is
interrupted.
.RT
.sp 1P
.LP
3.6
	\fILoop\ g\ \(em\ tributary digital loop towards the Muldex\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop (see Figure\ 2/R.115) with the output
polarity towards the tributary interface unit strapable to A\ or Z\ polarity.
Through this loop the channel data as received from the aggregate is looped
back to the aggregate towards the distant TDM equipment. This loop shall be
accomplished as close as possible to the internal tributary interface which 
can be located on the tributary interface unit or in the TDM central logic. 
.RT
.sp 1P
.LP
3.7
	 \fILoop\ h\ \(em\ tributary digital loop towards the tributary interface\fR 
\fIunit\fR 
.sp 9p
.RT
.PP
This loop is a one\(hyway loop with the output polarity towards the
muldex\(hypart of the given channel strapable to A\ or Z\ polarity. Through 
this 
loop the channel data at the tributary input is looped back to the channel
output through the tributary interface unit. This loop shall be accomplished 
as close as possible to the TDM central logic. 
.bp
.RT
.LP
.rs
.sp 15P
.ad r
\fBFigures 2/R.115, 3/R.115, 4/R.115, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR 	\fBUse of the loops\fR 
.sp 1P
.RT
.PP
Loops\ c and\ d may be used under remote control on international
links after bilateral agreements only.
.RT
.sp 2P
.LP
\fB5\fR 	\fBMethods of control\fR 
.sp 1P
.RT
.PP
5.1
Two types of control might be possible:
.sp 9p
.RT
.LP
	a)
	\fILocal control of a loop\fR 
.LP
	A loop is locally controlled when the loop request
originates at the location of the equipment to be looped.
.LP
	b)
	\fIRemote control of a loop\fR 
.LP
	A loop is remotely controlled when the loop request
originates at a location other than that of the equipment to be
looped.
.PP
5.2
When the aggregate modem is using a standard interface to the
TDM\(hyequipment, the implementation of the echo\(hyback function and the 
controls 
through the digital aggregate interface of loops\ b, c and\ d are left for
further study.
.PP
5.3
The control of loops\ a, b, c and\ d should be supervised by a time\(hyout
function. The time\(hyout function shall automatically open the loop after a
specified time period, measured from the closing of the loop. The length 
of the time period should be chosen from time intervals\ 5, 20 or 40\ seconds 
by 
bilateral agreement between Administrations.
.PP
The operation and test procedure for loop f to h is a national matter.
.sp 2P
.LP
\fB6\fR 	\fBControl signalling\fR 
.sp 1P
.RT
.sp 1P
.LP
6.1
	\fIAlternative A\fR 
.sp 9p
.RT
.PP
When the maintenance facilities are controlled by the software
within an exchange, a maintenance centre or a TDM terminal, a control
signalling code (CSC) is used where the control signalling characters on 
the selected maintenance channel shall be in accordance with Table\ 1/R.115 
(see 
also Recommendation\ U.12, Table\ 8/U.12).
.bp
.RT
.ce
\fBH.T. [T1.115]\fR 
.ce
TABLE\ 1/R.115
.T&
lw(66p) | lw(30p) | lw(18p) | lw(12p) | lw(18p) | lw(12p) | lw(72p) .
						
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/R.115 [T1.115], p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
A complete control signalling code character consists of one start element 
(Start), followed by four information elements (b\d0\u, b\d1\u, b\d2\u, 
b\d3\u) one parity element (b\d4\u),and a stop element (Stop) of nominally one
and a half unit element, see Figure\ 5/R.115.
.LP
.rs
.sp 10P
.ad r
\fBFigure 5/R.115, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
Bit b\d0\uis the least significant bit (LSB) and b\d3\uis the
most significant bit (MSB). For the transmission of decimal numbers from\ 
0 up to\ 99 the binary code should be used. The 8\ binary bits should be 
split into 
two characters, No.\ 1 and No.\ 2, character\ No.\ 1 holding the least 
significant bits and character\ No.\ 2 the most significant bits. 
.sp 1P
.LP
6.2
	\fIAlternative B\fR 
.sp 9p
.RT
.PP
When maintenance facilities do not use control signal according to Recommendation\ 
U.12, the signalling characters on the maintenance channel 
selected must conform to International Alphabet\ No.\ 5 (IA5), with an even
parity check (see Figure\ 6/R.115).
.RT
.LP
.rs
.sp 8P
.ad r
\fBFigure 6/R.115, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.3
	\fIMaintenance channel signalling\fR 
.sp 9p
.RT
.PP
Standardization of signalling on the maintenance channel is left
for further study.
.RT
.sp 2P
.LP
\fB7\fR 	\fBRouting of the maintenance control signals\fR 
.sp 1P
.RT
.PP
One 50\ baud channel, or a channel of more than 50\ bauds may be
allocated (on an optional basis) for maintenance purposes, where possible 
on a separate system using a parallel route. Where this option is exercised 
the 
allocation of the maintenance channel is specified within the respective 
CCITT Recommendation or bilaterally between Administrations. 
.PP
The selected maintenance channel should only be used for the
transmission of alarms, supervision and remote control signals.
.PP
When there is no possibility to use a separate system on a parallel
route the control of the loops\ c and\ d is left for further study.
.RT
.sp 2P
.LP
\fB8\fR 	\fBApplication\fR 
.sp 1P
.RT
.PP
It may be possible to apply the described maintenance technique to multiplexors 
conforming to Recommendations\ R.101, R.111 and other standardized multiplexors. 
.RT
.sp 2P
.LP
\fB9\fR 	\fBUse of the maintenance channel\fR 
.sp 1P
.RT
.PP
Use of the maintenance channel for purposes other than loop control is 
left for further study. 
\v'6p'
.RT
.sp 2P
.LP
\fBRecommendation\ R.116\fR 
.RT
.sp 2P
.ce 1000
\fBMAINTENANCE\ TESTS\ TO\ BE\ CARRIED\ OUT\ ON\ INTERNATIONAL\fR 
.EF '%	Fascicle\ VII.1\ \(em\ Rec.\ R.116''
.OF '''Fascicle\ VII.1\ \(em\ Rec.\ R.116	%'
.ce 0
.sp 1P
.ce 1000
\fBTDM\ SYSTEMS\fR 
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
	The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR 
.sp 9p
.RT
.PP
(a)
the savings to be made by reducing interruption time on
TDM links;
.PP
(b)
the importance of being able to determine responsibilities between the 
several parties who, of necessity are involved in maintenance 
questions for the networks;
.PP
(c)
the advantages of standardization regarding maintenance;
.PP
(d)
maintenance loops are standardized in
Recommendation\ R.115,
.sp 1P
.LP
\fIunanimously declares the following:\fR 
.sp 9p
.RT
.PP
that when the quality of the TDM\(hylink has deteriorated beyond the alarm 
limit or if the local muldex gives an alarm, supplementary measurement 
should be performed. The following test and supervision methods can be used.
.sp 2P
.LP
\fB1\fR 	\fBTesting and supervision of TDM systems\fR 
.sp 1P
.RT
.sp 1P
.LP
1.1
	\fIBit error rate\fR 
.sp 9p
.RT
.PP
The synchronization bits are supervised and an error rate alarm is issued 
when the error rate exceeds a preset limit, 10\uD\dlF261\u3\d, 10\uD\dlF261\u4\d 
or\ 10\uD\dlF261\u5\d.
.RT
.sp 1P
.LP
1.2
	\fIBit error counter\fR 
.sp 9p
.RT
.PP
All synchronization bit errors shall be registered in a cyclic
counter and it shall be possible to read the value of this counter by
command.
.bp
.RT
.sp 1P
.LP
1.3
	\fIRoutine supervision\fR 
.sp 9p
.RT
.PP
The operation of the TDM equipment and maintenance channel should continuously 
be supervised by a repetitive test signal. An alarm is issued when a correct 
acknowledgement is not received for a specified number of test 
signals. The alarm is reset automatically when the fault situation ceases.
.RT
.sp 1P
.LP
1.4
	\fIAlarm reset\fR 
.sp 9p
.RT
.PP
It shall be possible to reset all alarms from the local side. The command 
shall also be able to reset the error rate value. 
.RT
.sp 1P
.LP
1.5
	\fISystem alarms\fR 
.sp 9p
.RT
.PP
Failures that affect operation of the whole or a major part of the TDM 
equipment are classified as one category. The supervised functions 
are:
.RT
.LP
	\(em
	Carrier:
.LP
	Loss of carrier is detected by the data modem through
CCITT circuit\ 109 or the corresponding circuit.
.LP
	\(em
	Synchronization:
.LP
	Loss of synchronization is detected by the TDM
multiplexer in accordance with the respective CCITT
Recommendation.
.LP
	\(em
	Multiplexing logic:
.LP
	Failure of the TDM central logic is detected by
internal supervision facilities within the multiplexer.
.LP
	\(em
	Power:
.LP
	Failure of the power supply is detected when the
telegraph power supply exceeds tolerance limits.
.sp 1P
.LP
1.6
	\fIChanging of active side\fR 
.sp 9p
.RT
.PP
When the TDM equipment is duplicated the active side can be
changed by command or manually.
.PP
When the remote or local side is changed automatically or manually,
information about what side is executive must be sent when the change has 
been executed. 
.RT
.sp 1P
.LP
1.7
	\fILooptest on standby side\fR 
.sp 9p
.RT
.PP
When the TDM equipment is duplicated the standby modem can be
tested by the setting of loop\ b by command. The test result is sent over the
active maintenance channel.
.RT
.sp 1P
.LP
1.8
	\fIAutomatic restart\fR 
.sp 9p
.RT
.PP
When the remote TDM is automatically restarted, information shall be sent 
informing about the restart and alarm status. 
.RT
.sp 1P
.LP
1.9
	\fIAcknowledgement\fR 
.sp 9p
.RT
.PP
The acknowledgement consists of one character and should have the following 
values: 
.RT
.LP
	5
	acknowledgement;
.LP
	0
	not acknowledgement.
.sp 2P
.LP
\fB2\fR 	\fBFormat of the messages\fR 
.sp 1P
.RT
.PP
The messages which will be sent over the 50 baud maintenance
channel shall have the following structure:
.RT
.LP
	C\d1\uC\d2\uM\d1\uM\d2\u. |  |  | M\dn\u
.LP
	C\d1\uC\d2\u:
	Message category (two characters)
.LP
	M\d1\u\(emM\dn\u:
	Information (number of characters unlimited)
.PP
After the reception of a message at the receiving end, the
receiving end shall send one character to the originating end as an
acknowledgement of the reception.
.bp
.sp 1P
.LP
2.1
	\fIMessage categories\fR 
.sp 9p
.RT
.PP
The purpose of the message categories (called MC) is to give a
direct command or to inform the control equipment in an exchange, a maintenance 
centre or a TDM about what type of information the following message contains. 
.PP
The MC consist of two characters, and each character is a decimal
number from 0\ to\ 9. The numbers are coded according to alternative\ A 
(CSC) in Recommendation\ R.115. 
.RT
.sp 1P
.LP
2.2
	\fIInformation\fR 
.sp 9p
.RT
.PP
The information characters are a part of an order to the remote TDM equipment 
or information from the remote TDM\(hyequipment, depending on the 
Message Category Signal.
.PP
The number of information characters in a message is not limited.
.PP
The characters are decimal numbers from 0 to 9, coded according to
alternative\ A (CSC) in Recommendation\ R.115.
.RT
.sp 2P
.LP
\fB3\fR 	\fBMaintenance messages\fR 
.sp 1P
.RT
.PP
Using the format described in \(sc\ 2 the maintenance messages shall
have a message category and information as given in the table below:
.RT
.LP
.rs
.sp 34P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [1T1.116]\fR 
.ce
TABLE\ 1
.ce
\fBMaintenance messages\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(90p) | cw(36p) | cw(102p) .
Types of messages	Message category	Information
_
.T&
lw(90p) | cw(36p) | lw(102p) .
	C 1 C 2	M 1\(hyM n
.T&
lw(90p) | cw(36p) | lw(102p) .
Routine supervision	01	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
System alarm reset	02	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop a	03	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop b	04	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop c	05	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop d	06	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop g	07	M 1\(hyM 3: Channel No.
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop h	09	M 1\(hyM 3: Channel No.
.T&
lw(90p) | cw(36p) | lw(102p) .
Setting of loop f	10	M 1\(hyM 3: Channel No.
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Connection of automatic test eq.
 }	11	 {
M
1\(hyM
3:
Channel No.
M
4\(hyM
2
3:
Answer back (See Note)
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Disconnection of automatic test eq.
 }	12	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Distortion measurement on sub. line
 }	13	M 1\(hyM 3: Channel No.
.T&
lw(90p) | cw(36p) | lw(102p) .
Line measurements	14	 {
M
1\(hyM
3:
Channel No.
M
4:
Type of line
0 =
SC
1 =
DC
2 =
FS
M
5:
Type of measurement
0 =
Current
1 =
Voltage
2 =
Leakage to earth
3 =
Leakage betw. conductors
4 =
Level FS
5 =
Interface test
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
Change side	15	 {
M
1:
Side
b
0 =
0 A side executive
b
0 =
1 B side executive
b
1 =
0 Standby side halted
b
1 =
1 Standby side
working
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
Restart of control unit	16	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Read bit error counter	17	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Set loop b on remote standby side modem
 }	18	\(em
.T&
lw(90p) | cw(36p) | lw(102p) .
Open line alarm	26	 {
M
1\(hyM
3:
Channel no.
M
4:
Alarm
b
0 =
1 Alarm
b
0 =
0 No alarm
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/R.116 [1T1.116], p. 29\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T1.116]\fR 
.ce
TABLE\ 1 \fI(continued)\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(90p) | cw(36p) | cw(102p) .
Types of messages	Message category	Information
_
.T&
lw(90p) | cw(36p) | lw(102p) .
Distortion alarm	27	M 1\(hyM 3: Channel No.
.T&
lw(90p) | cw(36p) | lw(102p) .
Bit error rate	28	 {
M
1:
Failure rate
3 =
10\uD\dlF261\u3\d
4 =
10\uD\dlF261\u4\d
5 =
10\uD\dlF261\u5\d
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Results of distortion measurement sub. line
 }	29	 {
M
1 | 
2:
Number of measured transitions
M
3 | 
4:
Maximum distortion
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
Result of line measurement	30	 {
M
1\(hyM
1
0:
Test result
M
1 = 0
Level FS OK
M
1 = 1
Level FS not OK
M
2 = 0
Interf. OK
M
2 = 1
Interf. not OK
M
3 | 
4:
Voltage or current on wire\ 1 and resistance
between wire\ 1 and\ 2. Resistance to
earth,\ w.1
M
5 | 
6:
Voltage or current on wire\ 2 or resistance between
wire\ 3 and\ 4. Resistance to earth,\ w.2
M
7 | 
8:
Voltage or current on wire\ 3.
Resistance to earth,\ w.3
M
9 | 
1
0:
Voltage or current on wire\ 4.
Resistance to earth,\ w.4
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
System alarms	31	 {
M
1:
Type of alarm
b
0 =
1 Carrier alarm
b
0 =
0 No carrier alarm
b
1 =
1 Synchronization alarm
b
1 =
0 No synchronization alarm
b
2 =
1 Power alarm
b
2 =
0 No power alarm
b
3 =
1 Mux logic alarm
b
3 =
0 No Mux logic alarm
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Manually initiated change side
 }	32	 {
M
1:
Side
b
0 =
0 A side executive
b
0 =
1 B side executive
b
1 =
0 Standby side halted
b
1 =
1 Standby side working
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
 {
Looptest result from standby side
 }	33	 {
M
1:
Result
0
Test OK
1
Test not OK
 }
.T&
lw(90p) | cw(36p) | lw(102p) .
Automatic restart	34	
.T&
lw(90p) | cw(36p) | lw(102p) .
Bit error counter	35	M
.TE
.LP
1\(hyM
3:
Result
\fINote\fR
\ \(em\ The answer back message shall be sent using International
Alphabet No.\ 2.
.nr PS 9
.RT
.ad r
\fBTableau 1/R.116 [2T1.116], p. 30\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp