Abstract: A system for recording and reproducing an audio, video and/or data message with facility for automatically indicating lack of faithful reproduction of the message originally recorded, which comprises deriving a first data signal representative of the message, generating correlation signal bursts whose interval is determined by a characteristic of the data signal, recording the message and data and correlation signals on a recording medium, recovering from the recording medium the message for playback and the correlation signal, deriving a second data signal from the recovered message and predicting from the second data signal the instant when the recovered correlation signal bursts should occur, and providing an indication whenever the recovered correlation signal bursts do not occur as predicted.

Abstract: The invention provides for the recording of an audio message and subsequent playback thereof and includes a facility for establishing whether the playback message is an authentic reproduction of the original message. The facility is obtained by producing a first data signal indicative of the audio message and recording it together with the audio message and producing a second data signal indicative of the playback message, and comparing the first and the second data signals to establish that the playback is an authentic reproduction of the original message if parity exists between the data signals.