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If you check the narration discs for filmstrips, you will find that many of them had an audible cue tone on one side for manual machines, with the other side having a sub-audible tone (50 hz?) for automatic machines. Mike Biel [log in to unmask] -------- Original Message -------- Subject: Re: [ARSCLIST] voca-film technology From: Steven Smolian <[log in to unmask]> Date: Thu, August 02, 2012 10:03 am To: [log in to unmask] I seem to recall that the auto-slide feature, at least for the general public, arrived c. 1960. I remember the big too-doo about the Kodak multi-slide exhibit at Grand Cenral just before the 1963-4 World's Fair. When I worked there, I recall assembling shows for clients and adding the triggering beep which had to be at a certain frequencey. It went onto the "B" channel of a 2 track stereo tape. I think many transcription houses had switched to 12" discs, especially for the classroom market, as that's what I remember being the size player for the film- record player machines of that era. If anyone really cares, a look through the audio and educational audio supply books of the period will have an answer. Steve Smolian -----Original Message----- From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Art Shifrin Sent: Thursday, August 02, 2012 7:52 AM To: [log in to unmask] Subject: [ARSCLIST] voca-film technology Does anyone on this list know if the disks' tones were simply cues for the operator to advance the slides, and or, if a frequency-tuned circuit triggered the next slide? Shiffy