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
Recommendations 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 1 020 Hz is indicated, the  actual
frequency should be 1 020 Hz + 2 Hz -7 Hz in accordance with Recommendation 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.