In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Sparks-R-Fun wrote:

Kevin,

What comes to mind that might just do what you want is a VOX circuit.  VOX stands for Voice Operated Trans(X)mit.  People who use handheld radios for communication often like these circuits because they allow them to simply start talking without having to press a button to start the transmitter when they want to communicate.  Basically the circuit detects a certain level of sound and then switches on the transmitter for as long as the sound level persists plus some delay that allows for slight pauses or periods of lower volume.

This sounds like it should do exactly what you desire because the circuit will change its output state based upon whether or not it has detected any (loud enough) sounds recently.  Such a circuit can be found at  [url]http://www.rason.org/Projects/basicvox/basicvox.htm[/url], though there are many, many others around.  You may want to search for "VOX circuit".

You should be able to connect the PTT ("Push To Talk" - radio jargon) connection in the circuit I referenced directly to an SX pin configured for input since the transistor is simply pulling the connection to ground.

I hope this helps or at least gives you an idea where to look.

 - Sparks

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