1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0 ).42/$5#4)/.G0G0!.$G0G0%.%2!,G0G002).#)0,%3!#%33G0G00/).43G0G0&/2G0G0-!).4%.!.#%)45G134G0G0RecommendationG0G0- (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation M.120 was published in Fas
2、cicle IV.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 the Blue Book version and copyright conditions remain unchanged (see below).2 In this
3、 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 means, electronic ormechan
4、ical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.1 - Rec. M.120 1Recommendation M.120Fascicle IV.1 - Rec. M.120ACCESS POINTS FOR MAINTENANCEFor lining-up and fault localization it is proposed to define access points at boundaries such as betweenswitc
5、hing and transmission. A division of maintenance responsibilities can be achieved with the aid of line access points,digital path access points and analogue link access points. The following concepts are compatible with the divisionshown in Recommendations Q.45 (Figure 1/Q.45) 1 and Q.502 (Figure 1/
6、Q.502) 2.a) A line access point separates an analogue exchange from analogue or digital transmission see a) and b) ofFigure 1/M.120.Location and interfaces of line access points are defined in Recommendation M.565.b) A digital path access point separates a digital exchange from analogue or digital t
7、ransmission see c)and d) of Figure 1/M.120.Digital path access points are located at the input and output ports of digital paths. Interfaces are definedin Recommendation G.703 3.c) A line access point separates the digital exchange from the analogue transmission see e) ofFigure 1/M.120.d) An analogu
8、e link access point separates a digital exchange from an analogue transmission if line access ordigital path access is not provided. f) of Figure 1/M.120 shows as an example the collocation of atransmultiplexer with a digital exchange.Analogue link access points are located at the input and output p
9、orts of analogue links. Interfaces aredefined in Recommendation G.233 4.Normally line access points, digital path access points and analogue link access points are provided asequipment interface, e.g. accessible at distribution frames.2 Fascicle IV.1 - Rec. M.120d01-scFIGURE 1/M.120.D01 =References1
10、 CCITT Recommendation Transmission Characteristics of an International Exchange, Vol. VI, Rec. Q.45.2 CCITT Recommendation Interfaces, Red Book, Vol. VI, Rec. Q.502, ITU, Geneva, 1985.3 CCITT Recommendation Physical/Electrical Characteristics of Hierarchical Digital Interfaces, Vol. III,Rec. G.703.4 CCITT Recommendation Recommendations Concerning Translating Equipment, Vol. III, Rec. G.233.
