1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G02%#/-%.$!4)/.3G0G0/.G0G04%,%0(/.%37)4#().G0G0!.$G0G03).!,).#,!53%3G0G0!00,)#!“,%G0G04/G0G0)45G134G0G034!.$!2$3934%-33).!,G0G0,%6%,3G0G0!.$G0G03).!,G0G02%#%)6%23%.3)4)6)49)45G134G0G0RecommendationG0G
2、01 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation Q.112 was published in Fascicle VI.1 of the Blue Book. This file is an extract fromthe Blue 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
3、 the Blue Book version and copyright conditions remain unchanged (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 publ
4、ication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VI.1 - Rec. Q.112 1Recommendation Q.112Fascicle VI.1 - Rec. Q.1122.1 SIGNAL LEVELS AND SIGNAL RECEIVER SENSITIVITY2.1.
5、1 Standardized transmitted powerThe values of the standardized transmitted power for the different line and interregister signals are defined inthe relevant parts of the specifications for the CCITT Systems No. 4, No. 5, R1 and R2.Note - The level of leak current which might be transmitted to line,
6、for example when static modulators areused for signal transmission, should be considerably below signal level, as specified.2.1.2 Variations of the absolute power level of received signalsThe standardized absolute power level of the signalling current to be transmitted is fixed at the maximumvalue c
7、ompatible with circuit transmission requirements and the extreme values of absolute power level, betweenwhich received signalling currents may lie, depend on three factors:1) the overall loss and the variation with time of this loss of the international circuit (link-by-link signalling)or of the cha
8、in of international circuits (end-to-end signalling) at 800 Hz;2) the variation with frequency of the overall loss of these circuits, in relation to the nominal value at 800Hz;3) the tolerance on the transmitted absolute power level in relation to the nominal value.The operate level range of the sig
9、nal receivers about a nominal value should take account of these threefactors. In System No. 4, the operate range ( 9 dB) is appropriate for end-to-end signalling. The maximum number ofcircuits in the end-to-end signalling situation is normally three but more may be possible depending upon the actua
10、lconditions. In System No. 5 the operate range, ( 7 dB) for line signals and for register signals is appropriate for eachcircuit in link-by-link signalling. For the other CCITT systems see the relevant parts of their specifications.2.1.3 Maximum sensitivity of the signal receiverIt is desirable to limit the maximum sensitivity of the signal receiver, particularly on account of crosstalkbetween the GO and RETURN paths of a 4-wire circuit, leak currents, etc.
