ITU-T R.57-1988 STANDARD LIMITS OF TRANSMISSION QUALITY FOR PLANNING CODE - INDEPENDENT INTERNATIONAL POINT-TO-POINT TELEGRAPH COMMUNICATIONS AND SWITCHED NETWORKS USING 50-BAUD START-STOP EQUIPMENT
The CCITT,considering(a) that Administrations must agree on the composition of the international section and the national sections before setting up an international point-to-point telegraph circuit;(b) that for the interconnection of switched public or private national networks a plan for distributing telegraph distortion between national networks and international circuits connecting the international terminal exchanges is required;(c) that for this purpose, provisional standards, based on the results of practical experience and on studies ofthe composition of telegraph distortion,should be laid down for Administrations;(d) that on well-maintained channels,with modulation at the standard rate of 50 bauds,the values in Table 1/R.57 should not normally be exceeded on the trunk sections (see Recommendations R.53 and R.75).These values are valid whether the channels are amplitude or frequency modulated.
ITU-T R.57-1988 Referenced Document
ITU-T R.53 Permissible Limits for the Degree of Distortion on an International 50-Baud/120-Hz VFT Channel (Frequency and Amplitude Modulation) - Telegraph Transmission (Study Group IX) 2 pp*， 1989-01-01 Update
ITU-T R.75 Maintenance Measurements on Code-Independent International Sections of International Telegraph Circuits - Telegraph Transmission Study Group IX; 1 pp*， 1989-01-01 Update
ITU-T R.57-1988 history
1988ITU-T R.57-1988 STANDARD LIMITS OF TRANSMISSION QUALITY FOR PLANNING CODE - INDEPENDENT INTERNATIONAL POINT-TO-POINT TELEGRAPH COMMUNICATIONS AND SWITCHED NETWORKS USING 50-BAUD START-STOP EQUIPMENT