Tone detector

Posted on Apr 1, 2012

The detector circuit is made up a two-amplifier multiple feedback bandpass filter followed by an ac-to-dc detector section and a Schmitt Trigger. The bandpass filter (with a Q of greater than 100) passes only 5Q0 Hz inputs whch are in turn rectified by Dl and filtered by R9 and Ca

Tone detector
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This filtering action in combination with the trigger level of 5 V for the Schmitt device insures that at least 55 cycles of 500 Hz input must be present before the output will react to a tone input.

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