Recorded information verification system

PCT No. PCT/AU85/00130 Sec. 371 Date Mar. 11, 1986 Sec. 102(e) Date Mar. 11, 1986 PCT Filed Jun. 14, 1985 PCT Pub. No. WO86/00745 PCT Pub. Date Jan. 30, 1986.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.