1、CCITT FASCICLE IV-3 * m 4862593 0505387 3 m Test frequencies for supermastergroups are not shifted at f 80 Hz, as they are located in wide guard intervals and do not coincide with carrier leaks and pilot frequencies. Test frequencies 9008 kHz, 11 096 kHz and 11 648 kHz given in Recommendation M.460
2、should be shifted to avoid interferences between supermastergroup and mastergroup No. 7 and No. 9 pilot frequencies (see Recommendation M.350). Test signal levels should generally not exceed -20 dBmO. A level of - 10 dBmO may be used for master and supermastergroup measurements. When the measurement
3、 of Group No. 3 (see Recommendation M.330) is being made, the test signal at 103.92 kHz has to be blocked, otherwide it is necessary to make the correction for the loss at the frequency 103.92 kHz, caused by the 411.86 kHz reject filter. TABLE. 1/M.525 Frequencies of test signals Type of link Superm
4、aster group Master group Sup erg r o u p (4 kHz channels) Group (4 kHz channels) Frequencies (kHz1 8516.3*, 8760, 9004, 9256, 9504, 9792, 10 080, 10 324, 10 576, 10 824, 11 150, 11 400, 11 644, 11 895, 12 144, 12 387.4* 8 12.6*, 871.92, 93 1.92, 1055.92, 1 179.92, 1303.92, 1427.92, 1555.92, 1675.92,
5、 1799.92, 1923.92, 1983.92, 2043.7* 312.3*, 320.08, 328.08, 344.08, 360.08, 376.08, 392.08, 408.08, 432.08, 456.08, 472.08, 488.08, 504.08, 520.08, 536.08, 544.08, 551.4* 60.6*, 63.92, 67.92, 71.92, 75.92, 79.92, 83.92, 87.92, 91.92, 95.92, 99.92, 103.92, 107.7* Nofe - As a rule the frequencies mark
6、ed by an asterisk (*) cannot be used for measurements without traffic interruption. These frequencies may be used in the absence of traffic in the edge channels or a low level of test signai (below -45 dBmO). Recommendation M.530 READJUSTMENT TO THE NOMINAL VALUE OF AN INTERNATIONAL GROUP, SUPERGROU
7、P, ETC., LINK 1 General Before any adjustment is made to a link it must first be ensured that each regulated line section or higher-order link over which the link concerned is routed is correctly adjusted and that the level of the reference pilot at the transmitting end is correct. No readjustments
8、will be made on the link except under the direction of the control station, after consideration of measurement results. - 308 Fascicle IV.l - Rec. M.530 -/-Y -7 CCITT FASCICLE 1V.L * 48b2591 0505388 5 = 2 Links without a regulator 2.1 For links which use only one regulated line section, or one highe
9、r-order link, readjustment of levels to values as close as possible to their nominal value must be made systematically after any measurement or clearance of a fault. Any departure in excess of f 2 dB from the original line-up at the time the link was first established must be investigated to ensure
10、that there is no fault. 2.2 For links of more complex constitution, no readjustment need be made until the departure from the nominal value exceeds 0.5 dB (see the Note in 6 3 of this Recommendation). When the departure from the nominal value exceeds these limits, adjustment to a value as near as po
11、ssible to the nominal value should be carried out. Adjustment at the terminal station only is permissible within the limits of departure from the settings at the time of the previous reference measurements as a function of the distance to the origin of the link or to the nearest upstream automatic r
12、egulator, as given in Table 1/M.530. TABLE 1/M.530 Distance to origin or regulator Limit for departure from the settings noted for previous reference measurements beyond which the possibility of a fault should be investigated (see the note in 0 3 of this Recommendation) Up to 1000 km . 1000-2000 km
13、Above 2000 km . k 2 dB k 3 dB k 4 dB If, for the distance concerned, adjustment at the terminal station would cause departures greater than those permitted by the table, measurements should be made at all through-connection points to find if a fault exists. If a fault exists, it should be located an
14、d cleared. If no fault exists, but the change is due to normal causes, e.g. temperature changes, aging, etc., adjustments should be made at each through-connection point to bring the level of the reference pilot as near as possible to its nominal value before making a final adjustment at the termina
15、l station. 3 Links with a regulator No readjustment need be made until the departure from the nominal value measured at the input to the regulator exceeds f 4 dB. Any departure in excess of f 4 dB from the nominal value measured at this point must be investigated. Note - In determining the margins w
16、ithin which equipment should be readjusted, it has been found a relatively small range in which no action need be taken. This enables the staff to avoid waste of time in continually readjusting in order to compensate minor changes; a somewhat larger range in which the received level may be readjuste
17、d to as near the nominal value as possible by the terminal station, without having to ask intermediate stations to measure and/or readjust. (This is subject to the overriding proviso that the cumulative adjustment made at the terminal station must not exceed a certain amount relative to the settings
18、 noted when the last set of reference measurements was made); a range in which it must be assumed that a fault may exist which must be sought and cleared before any readjustment is permitted. After the fault (if any) has been found and all stations, intermediate and terminal, have, if necessary, rea
19、djusted their levels to as near the nominal value as possible, the new settings are noted for future reference purposes when making subsequent adjustments. useful to distinguish three ranges about the nominal value into which the received level might fall: - - - - t - I Fascicle IV.l - Rec. M.530 30
20、9 CCITT FASCICLE IV.3 * 4862593 0505389 7 W i The three ranges are shown in Figure 1/M.530 in relation to a typical distribution of level values. A suitable value for y in Figure 1/M.530 is considered to be 2 S, where S is the observed standard deviation. This concept is the basis of Table 1/M.530.
21、Nominal value 4 CCITT 36840 Ranges about nominal value r no action need be taken -x to +x readjustment at terminal station sufficient - y to - x and + x to + Y 1 a fault must be assumed +y FIGURE 1/M.530 Typical distribution of observed values of level, showing ranges in which different action is ne
22、cessary Recommendation M.535 SPECIAL MAINTENANCE PROCEDURES FOR MULTIPLE DESTINATION, UNIDIRECTIONAL (MU) GROUP AND SUPERGROUP LINKS The Recommendations covering the maintenance of groups and supergroups will apply as far as possible but there will be a number of new maintenance problems which are p
23、eculiar to multiple destination links. In particular, arrangements will be needed to check the performance of the MU main section of such links. In order to simplify the procedures and minimize interference to other users of the common path, it is recommended that the send reference station (see Fig
24、ure 1/M.460) for the MU main section should act as a focal point for reports and inquiries concerning the MU main section. The group, supergroup, etc., control stations will still be responsible for localizing a fault to a particular section of a link in accordance with Recommendation M.130. When a
25、fault is found to be in the communication satellite link, the send reference station will report the fault to the satellite control responsible for this link from baseband-in to baseband-out. When the fault is cleared, the send reference station will advise the MU main section controls which will in turn advise the group, supergroup, etc., controls concerned. - 310 Fascicle IV.l - Rec. M.535 1 I
