1、CCITT FASCICLE 1V.L * = 48b259L 0505385 T I! - is the same as the end of a line link without complete demodulation to the groups, supergroups or mastergroups (i.e. when only part of the groups, supergroups, etc., are through-connected direct from one line link to another, without passing via the thr
2、ough-connection equipment to the basic groups); avoid sending a measuring frequency that is the same as a pilot frequency of a following regulated line section (unless the pilot frequency on such a following section is protected by a blocking filter at the beginning of the section); take into accoun
3、t the possibility of attenuation to additional measuring frequencies lying at the edges of the frequency band of a through-connected basic group, supergroup, etc., due to the presence of through-connection filters. ii) Interference between additional measuring frequencies on adjacent coaxial links i
4、s possible if precautions are not taken to avoid carrying out simultaneous measurements on adjacent links. For this reason: a) there should be different dates for routine maintenance measurements on two adjacent links; b) before making any measurement using an additional measuring frequency, and esp
5、ecially those made when clearing faults, repeater station staff should see to it that measurements are not in progress on an adjacent coaxial link. the maintenance personnel should: a) b) 3 Symmetric pair regulated line section The following measurements should be made at regulated line section term
6、inal stations: a) b) daily reading of the line pilot level if necessitated by the type of system. It is preferable that such measurements should always be made at the same time of day; as necessary, readjustment to the nominal value as described in Recommendation M.510. The Administrations concerned
7、 are left to decide on measurements at additional measuring frequencies and on checking the operation of the regulators, if applicable. The same applies to any kind of measurement or pilot level reading at intermediate attended or unattended stations. References CCIR Recommendation Measurements of n
8、oise in actual traffic over radio-relay systems for telephony using frequency-division multiplex, Vol. IX, Rec. 398, ITU, Geneva, 1986. CCIR Recommendation Measurement of noise using a continuous uniform spectrum signal on frequency-divi- sion multiplex telephony radio-relay systems, Vol. IX, Rec. 3
9、99, ITU, Geneva, 1986. 11 2 Recommendation M.510 READJUSTMENT TO THE NOMINAL VALUE OF A REGULATED LINE SECTION (ON A SYMMETRIC PAIR LINE, A COAXIAL LINE OR A RADIO-RELAY LINK) After the routine measurement or clearance of the fault and when it has been ensured that no faults remain on the system, ad
10、justments should be made as necessary to bring the levels of the line pilots and additional measuring frequencies as close as possible to their nominal value. Making the whole adjustment in the receiving terminal station should be avoided; adjustments should be made where they are necessary, under t
11、he direction of the control or sub-control station concerned. Methodical readjustment should be carried out when the level measured at the terminal station exceeds the maintenance limits for the carrier system. Due allowance should be made for measuring errors and for random effects which may cause
12、slight short-term variation. The tolerance to be allowed depends on the type of system, its length and the periodicity of the measurements. For example, the following tolerances may be allowed: a) b) in the case of a system with continuous gain control an adjustment should be made only if an improvement of at least 0.3 dB can be obtained; in the case of a system with step-by-step gain control allow a permissible tolerance of f (one-half the gain control step f 0.3 dB). 306 Fascicle IV.l - Rec. M.510
