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More  Switch Circuits, Micropower Circuits

Audio Signal Detector/Switch Circuit
designed by David A. Johnson, P.E.
 

For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an Amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.   The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years.

Click on Drawing Below to view PDF version of Schematic

Circuit Audio Activated Switch Circuit designed by David Johnson, P.E. (June 30, 2006)

More  Switch Circuits

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