ITU-T R 53-1988 PERMISSIBLE LIMITS FOR THE DEGREE OF DISTORTION ON AN INTERNATIONAL 50-BAUD 120-HZ VFT CHANNEL (FREQUENCY AND AMPLITUDE MODULATION)《50Bd 120Hz国际音频电报电路(调频和调幅)的畸变容限》.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.0%2-)33)“,%G0G0,)-)43G0G0 amended at Arnhem, 1953,Geneva, 1964, Mar del Plata, 1968 and Malaga-Torremolinos, 1984)The CCITT,considering(a) that the numerous tests made on voic

2、e-frequency telegraph (VFT) equipment in service now make itpossible to establish limits for the degree of distortion outside which a VFT channel must be regarded as being out oforder;(b) that these tests should be made with reversals and with standard text at the modulation rate used foradjustment;

3、(c) that, when equipment is put into service and when it is adjusted, the minimum distortion should be soughtand therefore limits for the degree of distortion need not be established in this case,unanimously declares the view(1) that the degree of bias distortion of reversals (a sequence of equal le

4、ngth significant intervals each beingequal to the unit interval) on an international VFT channel at the modulation rate employed for adjustment should notexceed a value corresponding to 4% at the standard modulation rate of 50 bauds;(2) that the degree of isochronous distortion in service of an inte

5、rnational VFT channel on the standardized textshould not exceed 10%, and that the degree of inherent start-stop distortion, in service conditions, on standardized text,should not exceed 8%.Note These limits, except where otherwise stated, apply to a modulation rate of 50 bauds and take account ofthe accuracy of the measuring equipment. They are provisional and may be amended according to the technicaldevelopment of voice-frequency telegraphy and of studies of telegraph distortion.