1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.4/,%2!“,%G0G0,)-)43G0G0 amended at Geneva, 1980)The CCITT,considering(a) that, to facilitate the study of plans for the establishment of international telegraph circuits, it i
2、s convenientto set limits for the degree of isochronous distortion of telegraph circuits and channels;(b) that, for whatever purposes normally used, these circuits should be capable of use with start-stopequipment;(c) that, until detailed transmission planning standards are established for the trunk
3、 sections of internationaltelegraph circuits operating at modulation rates of 75, 100 and 200 bauds, the distortion limits mentioned below shouldbe regarded as provisional standards;(d) that the limits laid down are those that should be evident in service conditions on telegraph circuits,excluding t
4、he local lines and terminal equipment,unanimously declares the view(1) that circuits (excluding local lines and terminal equipment) should be established and maintained in such amanner that the degree of isochronous distortion will not exceed the limits shown in Table 1/R.120, irrespective ofwhether
5、 any form of regeneration is provided in the circuit or not;TABLE 1/R.120Modulation rate(bauds)Maximum degreeof isochronous distortion permitted7510020028 %24 %32 %(2) that the degree of isochronous distortion of each channel that may form part of a circuit should be as smallas possible, and should not in any case exceed 10%.
