1、CCITT FASCICLE IV-L * W 4862591i 0505386 li W Recommendation M.520 ROUTINE MAINTENANCE ON INTERNATIONAL GROUP, SUPERGROUP, ETC., LINKS 1 Type of routine tests Only measurements of the pilot level are made on international group, supergroup, etc. links. These do not involve other stations. Therefore,
2、 Administrations are free to decide on the methods and periodicities. In order to ensure that the performance limits of the links laid down in Recommendation M.160 are met, the following tests are recommended for consideration. 2 Links without an automatic regulator At control stations routine measu
3、rements should be made of the pilot level. The periodicity of these routines may be weekly or monthly depending on the complexity of the routing and constitution of the link. 3 Links with an automatic regulator At control stations where a regulator is installed, the level at the input and output of
4、the regulator, if these measurement points are provided by the equipment, may be measured every six months. 4 Continuous recording of pilot level In addition to the above it is useful to be able to take continuous pilot-recordings as required to detect fault conditions which do not trigger the norma
5、l alarm systems. Recommendation M.525 AUTOMATIC MAINTENANCE PROCEDURES FOR INTERNATIONAL GROUP, SUPERGROUP, ETC., LINKS 1 General In order to reduce corrective maintenance and minimize preventive maintenance in accordance with Recommendation M.20 the routine measurements of group, supergroup, etc. l
6、inks may be carried out by automatic measurements without interruption. Such routine measurements, where provided, should be for the same characteristics given in Recommenda- tion M.460, e.g. overall loss, random noise, etc. The decision to use automatic measurement procedures and the determination
7、of intervals between routine measurements are matters for agreement by the concerned Administrations. The need for readjustment based on the results of these measurements should be determined according to Recommendation M.530. 2 Frequencies and levels of test signals The recommended frequencies for
8、overall loss measurement are given in Table 1/M.525. The maintenance measurements can be made at some or all of those frequencies. The test frequencies for group, supergroup, etc. links are chosen to fall between channels, groups, supergroups, etc. These frequencies are shifted at f 80 Hz with respect to 4 kHz multiplied frequencies to avoid carrier leaks and other spurious tones interference. The automatic measurement equipment usually makes use of pre-defined software and/or hardware. 3 07 -i Fascicle IV.l - Rec. M.525
