1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2.!4)/.!,G0G0!.!,/5%G0G0#!22)%2G0G03934%-3%.%2!,G0G0#(!2!#4%2)34)#3G0G0#/-/.G0G04/G0G0!,!.!,/5%G0G0#!22)%2G1342!.3-)33)/.G0G03934%-3,).%G034!“),)49G0/2) to keep levels at the ends of regulated-line sections
2、 within such limits that regulators of the followingmultiplex equipment are able to function;3) to ensure that regulation is precise enough to make it generally unnecessary to provide an automatic groupregulator and/or supergroup regulator for the group, supergroup, etc., links set up on a single re
3、gulated-line section.It appears that all three objectives will be secured if levels at the end of the longest regulated section envisagedare stabilized to 1 dB at any frequency in the band transmitted.The CCITT therefore unanimously recommends that:Designers of line-regulating systems take account o
4、f the daily and seasonal variations in temperature to whichthe cables and repeaters are likely to be subjected, the predictable ageing of components, and also the nominal range ofvariation of power supplies, assuming that appropriate precautions are taken in the placing of the cable, in the design o
5、fbuildings and in regulation of power supplies.As a design objective for the residual effects of sustained power and temperature variations, and the predictableageing of components, over the ranges expected in any period between two successive manual adjustments, the changein insertion gain of a reg
6、ulated-line section at any frequency in the transmitted band should not exceed 1 dB.For the purposes of this Recommendation, it is assumed that a regulated-line section will not be longer than ahomogeneous section of the hypothetical reference circuit applicable to the type of system considered and
7、that theinterval between two successive manual adjustments will be not less than a fortnight.The variations in gain of a regulated-line section in service is also affected by maintenance operations andadjustments. The design objective excludes these effects.Moreover, the dynamic stability of the reg
8、ulating system should be such that any swinging of the gain isdamped and at a suitable rate as a result of an abrupt change in pilot level. If, for example, the pilot level is suddenlyincreased by 2 dB at the origin of the regulated-line section, the pilot level must not increase or diminish by more
9、 than 2dB at the end of the regulated-line section. The resulting fluctuations in pilot level must fall off progressively.Note - It may be desirable to specify immunity of the regulating system to interference from components oftelevision signals when transmitted.Reference1 CCITT Recommendation Stability of transmission, Vol. IV, Rec. M.160._1)Stability of transmission is also the subject of Recommendation M.160 of Volume IV 1.
