1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 0 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G042!.3-)33)/.G0G015!,)49/“*%#4)6%G0G0-%!352).G0G0!00!2!453!00!2!453G0G0&/2G0G04(%G0G0-%!352%-%.4/&G0G0)-05,3)6%G0G0./)3%)45G134G0G0RecommendationG0G00 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Rec
2、ommendation P.55 was published in Volume V 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
3、 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 publication may be reproduced or utilized in any form or b
4、y any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Volume V - Rec. P.55 1Recommendation P.55Volume V - Rec. P.55APPARATUS FOR THE MEASUREMENT OF IMPULSIVE NOISE(Mar del Plata, 1968)Experiments have shown that clicks or other impulsi
5、ve noises which occur in telephone calls come from anumber of sources, such as faulty construction of the switching equipment, defective earthing at exchanges andelectromagnetic couplings in exchanges or on the line.There is no practical way of assessing the disturbing effect of isolated pulses on t
6、elephone calls. A rapidsuccession of clicks is annoying chiefly at the start of a call. It is probable that these series of clicks affect datatransmission more than they do the telephone call and that connections capable of transmitting data, according to thenoise standards now under study, will als
7、o be satisfactory for speech transmission.In view of these considerations, the CCITT recommends that Administrations use the impulsive noise counterdefined in Recommendation O.71 1 for measuring the occurrence of series of pulses on circuits for both speech anddata transmission.Note At the national
8、level, Administrations might continue to study whether the use of this impulsive noisecounter is sufficient to ensure that the conditions necessary to ensure good quality in telephone connections are met. Inthose studies, Administrations may use whatever measuring apparatus they consider most suitable for example apsophometer with an increased overload factor but the CCITT does not envisage recommending the use of such aninstrument.Reference1 CCITT Recommendation Specification for an impulsive noise measuring instrument for telephone-type circuits,Vol. IV, Rec. O.71.
