1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% ).4%2.!4)/.!,G0G04%,%0(/.%G0G0#)2#5)434%34).G0G0/ convergence test; performance under conditions of double-talk-A; performance under conditions of double-talk-B; infinite return loss convergence t
2、est; tone disabler control signal detection sensitivity, DIS S; tone disabler control signal detection sensitivity, DIS R.(This list is provisional and is the subject of further study.)3 Cancellers permanently associated with national circuitsAdministrations should choose one of the following method
3、s of canceller testing: the use of ECTS or ECTS facilities as part of an ATME-type equipment (where this equipment isprovided at both ends of a circuit); or the use of an in-station tester. Tests to be performed are listed in 2.2.2 Fascicle IV.1 - Rec. M.6654 Testing of pooled cancellersWhen echo ca
4、ncellers are not permanently associated with circuits, Administrations should use an in-stationtester. Tests to be performed are listed in 2.2.5 Use of group-diagnosticsThis method of testing is under study. It comprises self-diagnostics which are shared between cancellers on aper rack or per shelf
5、basis and which perform tests similar to those of an in-station tester. The advantages of using thismethod are that tests can be made very frequently, thus obviating the need for routine testing, and that a failure can bevery quickly brought to the attention of maintenance staff.References1 CCITT Recommendation Echo cancellers, Vol. III, Rec. G.165.2 CCITT Recommendation CCITT automatic transmission measuring and signalling testing equipment ATME No. 2, Vol. IV, Rec. O.22.3 CCITT Recommendation In-station echo canceller tester, Vol. IV, Rec. O.27.
