Pulse generator for A-V recorders

AV recorders used in audio-video presentations contain an additional head to read and write the control pulses for the slide projector. These pulses are normally used to actuate a relay that operates the projector, The pulse data are usually written on one of the audio tracks at the non-used side of the tape. Since the extra head in modern recorders does not make use of the two standard audio tracks, tt becomes possible to have stereo sound for the presentation. This does mean, however, that only one side of the cassette can be used.