8.	Recommendation G.712



PERFORMANCE CHARACTERISTICS OF PCM CHANNELS

BETWEEN 4-WIRE INTERFACES AT VOICE FREQUENCIES



(Geneva 1972, further amended)





	The CCITT



recommends



	that the performance characteristics which follow should be met between 
the voice-frequency ports of PCM channels coded in accordance with 
Recommendation G.711.



	The performance limits to be quoted are to be considered as Recommen-
dations to be met in all cases.



	Except where indicated otherwise, the values and limits specified are 
those which should be obtained in 4-wire measurements using two PCM 
multiplex terminal equipments connected back-to-back and with the 
input and output ports of the channels terminated with their nominal 
impedance (except where specified in §3.3 below).



	To avoid level errors produced as a result of the use of test frequencies 
which are sub-multiples of the PCM sampling rate, the use of integer 
sub-multiples of 8 kHz should be avoided.



	Where a nominal reference frequency of 1020 Hz is indicated, the actual 
frequency should be 1020Hz + 2 Hz -7 Hz in accordance with Recom-
mendation 0.6.



	For an interim period Administrations may, for practical reasons, need to 
use a reference frequency of nominally 800 Hz, but slightly offset from 
this value to avoid sub-multiples of sampling frequency.