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.