🚀 go-pugleaf

In article <1993Jan25.183720.12910@tellab5.tellabs.com> chrz@tellabs.com (Peter Chrzanowski) writes:
>In article <1993Jan20.104438.5447@ucc.su.OZ.AU>, andy@extro.ucc.su.OZ.AU (Andrew Miehs) writes:
>> G'day,
>> 
>> I'm not much in the know about electronics (but I'm learning) and so I'd 
>> appreciate anybody's help in designing the following:
>> 
>> I need a circuit that reacts to a certain high-frequency sound, in order to
>> activiate another circuit. Is that clear? In other words, when a microphone
>> picks up the sound wave from a nearby source, it turns some auxilary circuit
>> on and it stays on until the sound wave ceases.
>> 
>> Please e-mail me with any suggestions or references.
>
>Look at the schematic (Howard Sams, etc.) of a TV made sometime before the
>late '70s.  Old TVs used remote controls that used unmodulated ultrasonics:
>just provide enough energy at the right frequency and the function would
>be triggered.
>

I think we've moved a bit further since then. How's about using a 567 tone
decoder. It's an 8 pin DIP that uses an RC circuit to set the center
frequency and has a sharp bandpass filter around that freqency. It'll
even give you the modulated output without the carrier frequency if you
wanted to do some futher processing. Cost about $1 apiece at most electronic
supply places.

BAJ

>> 
>> Malcolm Ryan
>> 
>> (care of Andrew Miehs - email andy@extro.ucc.su.OZ.AU)
>> 
>> -- 
>> +-------------------------------+---------------------------------------------+
>> | Andrew Miehs                  |                                             |
>> | Mail: andy@extro.ucc.su.oz.au |       $$$ THIS SPACE FOR RENT $$$           |
>> | NB:   Don't call me andy!     |                                             |
>
>


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Another random extraction from the mental bit stream of...
Byron A. Jeff - PhD student operating in parallel!
Georgia Tech, Atlanta GA 30332   Internet: byron@cc.gatech.edu