1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0 ).42/$5#4)/.G0G0!.$G0G0%.%2!,G0G002).#)0,%3#)2#5)4G0G04%34).)45G134G0G0RecommendationG0G0- (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation M.110 was published in Fascicle IV.1 of the Bl
2、ue 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 Recommendation, the
3、 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 ormechanical, including phot
4、ocopying and microfilm, without permission in writing from the ITU.Fascicle IV.1 - Rec. M.110 1Recommendation M.110Fascicle IV.1 - Rec. M.110CIRCUIT TESTING1 Access points for testing purposesAccess points are required to enable lining-up and subsequent maintenance operations to be performed oninter
5、national circuits. The required access points are as follows:1.1 Recommendation M.565 describes and defines the access points needed for international public telephonecircuits, these points being referred to as “circuit access points” and “line access points”.Line access points and circuit access po
6、ints (or appropriate means for reaching the circuit access points) shouldbe provided for testing all circuits which are used for the provision of international telecommunication services.Where a circuit uses channel associated signalling, it should be possible to identify and measure at the circuita
7、ccess points, the signal-transmission parameters, e.g., type of signal, sequence, timing, duration, level and frequency.1.2 Test access points should also be provided for circuits connected through a repeater station in transit from onecountry to another. Such access points are known as “intermediat
8、e access points”.1.3 On a leased circuit, the circuit access points are regarded as being located in the renters premises, at thedemarcation point where connections are made to the terminal equipment used on the circuit1).1.4 Test access points should also be available at the terminal international
9、centre for circuits terminating withinthe country at a place remote from the international centre, for example, in the premises of the users of leased circuits orin a voice-frequency telegraph terminal station, etc. Such access points, known as line access points, should be availabledirectly or indi
10、rectly to the transmission maintenance point (international line) as defined in Recommenda-tion M.1014 1 for such circuits.1.5 In addition to those mentioned in 1.1 to 1.4 above, access points should be provided on the audio input andoutput of FDM channel multiplex and primary PCM multiplex equipmen
11、ts.1.6 Access points for testing purposes should be provided on all primary order digital paths. Such access points,known as digital path access points, should be located as near to the ends of the digital path as possible.With suitable digital test equipment, such digital path access points enable
12、in-service circuit monitoring to becarried out when, for example, digital paths are directly interfaced with digital exchanges or transmultiplexers.When the digital path is out of service, this same point can be used to transmit and receive signals for bothdigital path and circuit testing.1.7 Figure
13、 1/M.110 shows an example of the basic access points for international telephone circuits terminated onan analogue exchange, and for a variety of other telephone-type circuits. Figure 2/M.110 shows the basic access pointsfor telephone circuits terminated on a digital exchange. Figures 1/M.110 and 2/
14、M.110 both show that remote access hasbeen provided to the “circuit access points” of automatic telephone circuits.1.8 Series M Recommendations relating to the various types of international circuits specify how the above-mentioned access points should be used for line-up and maintenance purposes._1
15、)The access points required for digital leased circuits have yet to be specified. This matter is for further study by Study Group IV,in association with Study Group XV.2 Fascicle IV.1 - Rec. M.110d01-scFIGURE 1/M.110.D01 =Fascicle IV.1 - Rec. M.110 3d02-scFIGURE 2/M.110.D02 =2 Measuring and testing
16、equipment2.1 The basic types of measuring equipment needed in an analogue environment are: signal generators (fixed and variable frequency oscillators and calibrated sending units), level-measuring sets, calibration units, psophometers, standard frequency source (or access to such a source), equipme
17、nt for signalling tests.In addition, delay distortion measuring equipment, frequency counters, interruption recorders, programmemeters, impulsive noise counters, phase jitter meters, automatic transmission measuring equipment, and equipment fornon-linear and total distortion measurement may be requi
18、red.2.2 The basic types of test and measuring equipment needed in a digital environment are as mentioned in 2.1above. This need can be met by equivalent digital test/measuring equipment, or by analogue equipment and the use of a“test coder/decoder” to convert digital access points to analogue access
19、 points. In some situations, testers for thefollowing will prove useful: bit error ratio; error-free or errored seconds; code violations; timing jitter; frame alignment.4 Fascicle IV.1 - Rec. M.1102.3 The actual requirements for a particular testing centre will depend upon the types of circuit exist
20、ing at thatcentre, and the range of tests and measurements that are specified for those circuits in the relevant Series MRecommendations. Reference should also be made to the “facility” requirements specified for the testing points definedin Recommendations M.717, M.718 and M.719.2.4 The implementat
21、ion of the worldwide transmission and switching plans makes it necessary for internationalcircuits to be lined up and maintained to a very high degree of accuracy.It is essential, therefore, to use measuring equipment of high accuracy and stability in order that themaintenance requirements given in
22、the relevant Series M Recommendations for circuits are met, and to ensureuniformity of measurement results.To this end it is desirable that measuring equipment provided for lining-up and maintaining all classes ofcircuits should, wherever possible, conform to the measuring instrument specifications
23、given in the Series ORecommendations. Where no CCITT specification is available, the best order of accuracy and stability should beprovided, consistent with cost and type of measurement to be made.Reference1 CCITT Recommendation Transmission maintenance point international line (TMP-IL), Vol. IV, Rec. M.1014.
