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Subject: Re: frequency detection requirements

Date: 02/25/01 at 10:55 AM
Posted by: Brian Snell
E-mail: bsnell@lara.on.ca
Message Posted:

In Reply to: frequency detection requirements posted by Jeremy Kelly on 02/10/01 at 10:32 AM:

Greetings.
I have used similar systems to what you are suggesting. One used a separate track on the tape to record a 1KHz pilot-tone burst which, when replayed, was detected and used to trigger a relay for synchronised slide changing. There is even an ANSI spec published on this for Professional AV applications. The other used a sub-sonic burst at 60Hz mixed in with the audio -- on playback the "listening" audio was passed through a L.F. filter to attenuate the 60Hz before being passed through the audio chain. Likewise, the "audio" was filtered out to leave the 60 Hz which was used in the "relay" amplifier.
If you wish it, I could probably draw up something which should work O.K. in your application. Please advise.


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