1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 5 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(G0G037)4#().3).!,).G0G0/6%2G0G02!$)/G0G0!.$G0G0-5,4)0,%8%$#(!%,32%15)2%-%.43G0G0(b) that it is essential to transmit the full range of telex signals for types A, B and C signalling;unanimously declare
2、s the view(1) that where it is necessary to receive signals with a nominal cycle of 7 units (see the Recommendation citedin 1), it will be necessary to insert suitable storage to reconcile the two character rates (400 and 411 per minute);(2) that type A and B signals in accordance with Recommendatio
3、n U.1 and U.2 and type C signals inaccordance with Recommendation U.11 should be accepted for transmission through the synchronous system.However, in the case of type A signalling, the delay between the start of the call-confirmation signal and the proceed-to-select signal should be increased to, at
4、 least, 150 ms;(3) that the call signal should be transmitted through the synchronous system with the minimum delayobtainable with the particular method of multiplexing in use, e.g., element interleaving, in order to reduce the incidenceof headon collisions with bothway operation. The maximum delay
5、due to the multiplex equipment should be limitedto 60 ms;(4) that the maximum delay on the callconfirmation signal due to the multiplex equipment should be 60 ms inthe case of type A signalling, and 120 ms in the case of type B signalling;(5) that the maximum delay on the start of the receptionconfi
6、rmation signal due to the multiplex equipmentshould be 60 ms in the case of type C signalling;(6) that the maximum delay on the proceed-to-select signal due to the multiplex equipment should be 450 msin the case of type A signalling, and 120 ms in the case of type B signalling;(7) that the maximum d
7、elay on the call-connected signal due to the multiplex equipment should be 450 ms(type A and type B signalling);(8) that the maximum delay on a teleprinter character due to the multiplex equipment should be 450 ms;(9) that the maximum delay on the clear and clearconfirmation signals due to the multi
8、plex equipment shouldbe 450 ms;(10) that the tolerance of the type A and B pulse signals after retransmission through the synchronous multiplexsystem will be stated below:a) Call-confirmation and proceed-to-select signal type B signallingThe duration of the pulse after transmission through the synch
9、ronous system will not be less than 17.5 msnor more than 50 ms.b) Dial pulses type B signallingSpeed 3% of the mean speed of input measured for digit 0 (normally 9 to 11 pulses per second).Ratio The duration of stop polarity pulses will not be less than 32 ms; the duration of start polaritypulses wi
10、ll not be less than 44 ms.Under certain circumstances the retransmitted dial signals may include pulses of stop polarity havingdurations of up to 73 ms and pulses of start polarity having durations of up to 98 ms. Where this is so andthe incoming switching equipment cannot accept pulses with these c
11、haracteristics a dial pulse regeneratorshould be inserted between the output of the multiplex circuit and the input of the switching equipment.2 Fascicle VII.2 - Rec. U.24c) Service signals for ineffective calls type B signallingThe duration of the period of stop polarity, whether followed by telepr
12、inter signals or not, will, aftertransmissions through a synchronous system, be not less than 145 ms and not more than 292 ms.If several synchronous systems are placed in tandem, the duration of the period of stop polarity of theservice signal at the output of this group of systems should not exceed
13、 440 ms.At the input of a synchronous system, a type B service signal will cause the return of a clearconfirmationsignal from the synchronous equipment without waiting for the return of the clearconfirmation signalfrom the distant end of the connection. Following the recognition of the clearing sign
14、al in the servicesignal, permanent start polarity will be transmitted over the synchronous system.d) Callconnect type A signallingThe duration of the pulse of start polarity after transmission through several synchronous systems will bewithin the limits 140 ms to 160 ms.Fascicle VII.2 - Rec. U.24 3A
15、NNEX A(to Recommendation U.24)TABLE A1/U.24Telex signalling through the multiplex equipment Type A signallingSignallingconditionSignal received from telex(Recommendation U.1)Signal on channelaggregate pathSignal transmitted to telexFree line Continuous A polarity on both signaling pathsContinuous A
16、polarity Continuous A polarityCall Inversion to Z polarity on forward signalling pathInversion to Z polarity (within 9-35 ms from inversion in column 2)(see Notes 1 and 2)Inversion to Z polarity (maximum delay of 60 ms from inversion in column 2)Call-confirmation Inversion to Z polarity on backward
17、path within 150 ms of receipt of calling signalAs for call As for callProceed-to-select Teleprinter signals or40 ms pulse of A polarity( 8 ms) on backwardpath. Not to be returned within 150 ms of call-confirmationTeleprinter signals or com-bination No. 22 (V)Teleprinter signals or combinationNo. 22
18、V) (see Note 3)Selection Teleprinter signals on the forward pathTeleprinter signals Teleprinter signals (see Note 3)Call-connect Teleprinter signals or 150 ms ( 11 ms) pulseof A polarity followedby continuous Z polarityfor 2 seconds minimumon the backward pathTeleprinter signals or one combination
19、followed by continuous Z polarity for2 seconds minimumTeleprinter signals or 145 5/6 ms pulse ofA polarity followed by continuousZ polarity for 2 seconds minimum(see Note 3)Service signals Teleprinter signals on the backward path followed by clearing signal(see Note 4)Teleprinter signals fol-lowed b
20、y one or two combinations and then continuous A polarity(see Note 5)Teleprinter signals followed by continuous A polarity (see Note 3)ClearInversion to continuous A polarity on either signallingpath (see Note 4)One or two combinations followed by continuous A polarity (see Note 5)Inversion to A pola
21、rity (see Note 3)Clear-confirmation Inversion to continuousA polarity in opposite direction to clearing aftera delay of 350-1500 ms following receipt ofclearing signalAs for clear As for clearFor notes, see Table A-3/U.24.4 Fascicle VII.2 - Rec. U.24TABLE A-2/U.24Telex signalling through the multipl
22、ex equipment Type B signallingSignallingconditionSignal receivedfrom telex(RecommendationsU.1 and U.2)Signal on channelaggregate pathSignal transmittedto telexFree line As for type A As for type A As for type ACall As for type A As for type A As for type ACall-confirmationA 17.5-35 ms pulse ofZ pola
23、rity on the back-ward signalling path,returned within 150 msof receipt of callingsignal1 or 2 consecutive elements of Z polarity32-50 ms pulse of Z polarity(see Note 7)Proceed-to-selectAs call-confirmationsignal. The interval ofA polarity separatingthe signals to be 100 ms minimumAs for call-confirm
24、ation As for call-confirmation. The interval separating the pulses may be reduced to 60 ms minimum (see Note 7)SelectionsignalsTeleprinter signals ordial pulses having the following limits:Speed: 9-11 p.p.s.Ration: 1Z: 1.9ATeleprinter signals (seeNote 2) or dial pulses,when each start polarityinterv
25、al is transmitted as1-4 elements of A polarityand each stop polarityinterval is transmitted as1-3 elements of Z polarity.The mean speed of pul-sing will be the same( 3%) as the inputsignals (see Note 6)Teleprinter signals (see Note 3) or dial pulses at the same mean speed of the input ( 3%) and havi
26、ng the following ratio limits:A polarity intervals: 44-98 msZ polarity intervals: 32-73 msCall-connectContinuous Z polarityfor 2 seconds minimumon the backward signal-ling pathOne combinationfollowed by continuousZ polarity for 2 secondsminimum (see Note 6)Continuous Z polarity for 2 seconds minimum
27、 (see Note 7)Service signals(busy pulse)165-260 ms of Z polarityon the backward pathfollowed by A polarityfor 1500 ms ( 30%)continuously repeated.The Z polarity periodmay be followed by teleprinter signals whenthe tolerance of theA polarity period isreduced to 20%One ot two signalsfollowed (possibly
28、) byteleprinter signals, thenby one combinationand A polarity as in theinput signal (see Note 6)145-292 ms Z polarity, followed (pos-sibly) by teleprinter signals and thenby A polarity of minimum duration 950 ms (see Note 7)Clear andclear-confirmationAs for type A As for type A As for type AFor note
29、s, see Table A-3/U.24.Fascicle VII.2 - Rec. U.24 5TABLE A-3/U.24Type C signalling effected by multiplex equipmentSignallingconditionsSignal received from telex(Recommendation U.11)Signal on channelaggregate pathSignal transmitted to telexFree line Continuous A polarity on both signalling pathsContin
30、uous A polarity Continuous A polarityCall signal(or automaticretest signal)Inversion to Z polarity on the forward path for 150-300 ms followedby teleprinter signalsInversion to Z polarity (within 9-35 ms from inversion in column 2)(see Note 1 and 2)Inversion to Z polarity (maximum delay of 60 ms fro
31、m inversion in column 2).The period of Z polarity may be lengthened by 450 ms maximumReception-confirmation(or receivingequipmentcongestionsignal)Inversion to Z polarity on the backward path for 450 ms ( 10 %) followed by teleprinter signals (or clearingsignal)As for call As for callClear andclear-c
32、onfirmationAs for type A As for type A As for type ANotes concerning Tables A1 /U.24 to A 3/U.24Note 1 Pulses of Z or A polarity from 09 ms ( 1 ms) should be rejected by the multiplex equipment.Note 2 The startstop stores of either signalling path should be switched into circuit after a maximum dela
33、y of one combinationfor all types of signalling except type B with dial selection.Note 3 Recognition time of the clearing signal is 300-1000 ms.Note 4 The startstop stores of either signalling path should be switched out of circuit after a maximum delay of two combinations.Note 5 For type B signalli
34、ng with dial selection the start-stop stores of both signalling paths will be switched into circuit afterrecognition of a maximum delay of one combination on the backward path with Z polarity on the forward path.Note 6 In order to meet the timing requirements of the type B service signals it may be
35、necessary to delay the initial inversion to Zpolarity by an amount (450 ms maximum) corresponding to the delay with teleprinter signals. The callconnect signal may also besimilarly delayed. However, reversion to A polarity within 50 ms indicating a type B callconfirmation or proceedtoselect signalsh
36、ould cancel any further delay on the transmission of these signals.Note 7 Delays given in these tables do not include the propagation time of voicefrequency telegraph channels.Reference1 CCITT Recommendation Transmission characteristics of the load end with its termination (ITA No. 2),Rec. S.3, 1.6.
