ITU-T R 83-1988 CHANGES OF LEVEL AND INTERRUPTIONS IN VFT CHANNELS《音频电报通路中电平的变化和中断》.pdf

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1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.#(!.%3G0G0/amended at Geneva, 1964)The CCITT,considering(a) that an alarming situation for the telegraph service has been created by interruptions on voice-frequencytelegraph

2、(VFT) channels, and by changes of level that have the same effect as interruptions;(b) that the consequences are such that, at present, the error rate that is attributed to VFT channels is still veryfar above the tolerable limit fixed by considerations of operational requirements (see Recommendation

3、 R.54, a) and f);(c) that certain Administrations have observed an improvement in the situation, and that this improvementseems to result from the measures taken by the telephone services, for instance, symmetric percussion tests, precautionsin the switching or power supplies, etc.;(d) that it has b

4、een confirmed that the number of interruptions increases markedly during the normal hourswhen maintenance staff are present, and is reduced when, despite very heavy traffic, maintenance is suspended, so thattelegraph Administrations are now convinced that one of the principal causes of interruptions

5、 on telegraph channels isintervention by maintenance personnel and perhaps by operating personnel;(e) that it has also been observed that the number of interruptions appears greater on international circuits thanon national circuits,unanimously declares the viewthat the drive against interruptions s

6、hould be continued vigorously and that, in order to observe the progress ofthis drive, Administrations should continue to make symmetric observations of the frequency and duration ofinterruptions on voice-frequency telegraph channels,and draws the attentionof the maintenance Study Group especially to the study of practical measures to remedy the situation.