1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 5 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(G0G037)4#().%.%2!,2%15)2%-%.43G0G04/G0G0“%G0G0-%4“9G0G02%.%2!4)6%G0G02%0%!4%23).G0G0).4%2.!4)/.!,G0G0#/%#4)/.3)45G134G0G0RecommendationG0G05 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation U.
2、5 was published in Fascicle VII.2 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchange
3、d (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any mea
4、ns, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VII.2 - Rec. U.5 1Recommendation U.5Fascicle VII.2 - Rec. U.5REQUIREMENTS TO BE MET BY REGENERATIVE REPEATERSIN INTERNATIONAL CONNECTIONS(former CCIT Recommendation E.5, Geneva, 195
5、6;amended at Geneva, 1964, Mar del Plata, 1968 and Geneva, 1976)The CCITT,considering(a) that it may be desirable to include regenerative repeaters in teleprinter switching networks;(b) that the only signals other than teleprinter signals that must be transmitted by a regenerative repeater are thecl
6、earing signal and the call-connected signal (see 3.1.3 below), since all other signals can be bypassed;(c) that other signals may be transmitted by regenerative repeaters,unanimously declares the view1 that, when regenerative repeaters are used in switching systems, the clearing signal should be ret
7、ransmitted witha minimum of delay. This delay is of course the same as for the transmission of teleprinter signals;2 that to ensure the correct retransmission of the call-connected signal (see 3.1.3 below) and the clearing signal,the regenerative repeater must not automatically insert the stop eleme
8、nt in either of these signals;3 that for other signals that may pass through regenerative repeaters, the tolerances at the origin and afterretransmission through the regenerative repeaters are as stated below.Note The characteristics and tolerances quoted are for the signals at the origin. The toler
9、ances at the input tothe regenerative repeater will depend on the degree of distortion in the transmission path from the origin to the input ofthe regenerative repeater. The tolerances at the output will depend on the normal tolerances for the regenerativerepeater.3.1 Pulse signals3.1.1 Call-confirm
10、ation (proceed-to-select) signal. Type B signallingA pulse of stop polarity of duration from 17.5 to 35 milliseconds. The nominal duration of the pulse afterretransmission through the regenerative repeater should not be less than 20 milliseconds or more than 40 milliseconds.Note This signal will be
11、transmitted over only one international trunk circuit and should thus normally passthrough not more than one regenerative repeater.3.1.2 Dial selection signals. Type B signallingThese signals have been standardized (Recommendation U.2) at a dial speed of 10 pulses per second 10%,and a pulse ratio (s
12、tart/stop) between the tolerance of 1.2:1 and 1.9:1 with a nominal ratio lying between 1.5:1 and1.6:1. Such signals after retransmission through several regenerative repeaters should not fall outside the tolerancesstated above.3.1.3 Call-connected signal. Type A signallingA pulse of start polarity l
13、asting 150 11 milliseconds. The nominal duration of the pulse after retransmissionthrough several regenerative repeaters should be within the limits of 140 to 160 milliseconds.2 Fascicle VII.2 - Rec. U.53.1.4 Busy signal Type B signallingPulses of stop polarity lasting 165-260 milliseconds, separate
14、d by intervals of start polarity lasting 1.5 seconds 30%. After retransmission through several regenerative repeaters neither the pulses nor the intervals should beshortened by more than 10%.3.2 Sequence signals (involving a single change of polarity)3.2.1 Calling signal. Types A and B signalling3.2.2 Call-connected signal. Type B signallingThese signals (inversion from start to stop polarity) have no timing tolerances as such. It is, however, essentialthat they should be retransrnitted by a regenerative repeater with a minimum of delay which in no case should exceed20 milliseconds.
