projector film changer

Posted on Feb 6, 2014

In synchronizing the audio and the projected film, a tone code must be used. This tone code triggers a device which automatically changes the film or slide. To do this you need a two channel tape recorder. The normal audio program must be recorded in one channel and the tone code must be recorded in the other channel. The tone code channel is then

projector film changer
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connected to a decoder circuit. The decoder circuit in turn is connected to the remote film/slide changer terminals of the projector. Diagram 49. 0 is the tone encoder. During audio programming. The button S1 must be pressed everytime one wishes to change the film/slide so that the tone code will be recorded into the tape. During replay, the film changes automatically being triggered by this tone code. The second circuit (diagram 49. 1) is the tone decoder. The relay contacts are connected to the remote terminals of the slide projector. The actual connections depend on the design of the projector ( it can be normally open or normally closed - check your projector`s handbook). By correct programming of the tone, one can also make the film change in the reverse direction. Depending on the type of projector, it is done by either recording a single long tone or two successive short tones.

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