A method for signalling between an analogue pulse coded modulation modem and a digital PCM modem

摘要

A method for detecting impairments present in digital signals transmitted by a digital PCM modem, comprises the steps of sequentially transmitting a plurality of descriptions of sequences of symbols S 1 ,S 2 ...S L an analogue PCM modem to the digital PCM modem, and requesting the digital PCM modem to transmit respective corresponding sequences of symbols. The received sequences of symbols (Fig.2) are compared by the analogue PCM modem with the requested sequences of symbols and stored for cross referencing during subsequent communication. Each described sequence of symbols is transmitted to detect at least one impairment in the corresponding sequence of symbols transmitted by the digital PCM modem, and each described sequence of symbols is transmitted for detecting an impairment different to the impairments to be detected by the other transmitted descriptions of sequences of symbols.