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Discussion Starter · #1 ·
Gadgetman was looking for a schematic to use his Chatterbox headsets, so I thought that I would post this.
The upper part of the circuit is to control a relay from the bikes PTT to extend the battery life. The relay contact is only closed to power the microphone when the PTT is held when transmitting on the CB, thus extending battery life. This may not be useful in applications where you may want to use the mics for intercom?

The lower part of the schematic is the meat and potatoes. It contains the bias circuit to make an electret microphone operate using a 9 volt battery. The switches and resister arraignment is to adjust gain and eliminate as much background noise as possible.
You may want to play around with different resister values to get the gain where you want it. You can ignore the connector pin #s, they were only relevent to my design

U1 is a simple comparitor circuit that can be made up from many different ICs. Using the IC to turn on the transistor makes the current draw from the bikes PTT circuit incredably low. I don't remember which I used but keep in mind that the pin out will be different for different ICs

 

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Thanks, Bill! :)

It looks a lot simpler than I had expected, but I am wondering why you have a capacitor above the 9V battery...wouldn't that prevent biasing the electret mic? Or, are you depending on some leakage current across the capacitor to maintain the 9V bias? Would a suitable choke do the same thing?

Thanks,
Arthur
 

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Discussion Starter · #3 ·
Sunkist,

That isn't a capacitor, it is a contact of the relay. When PTT is present the relay is energized to close that contact and complete the circuit.
 

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Discussion Starter · #5 ·
Gadgetman,

My app was using a computer type of microphone on the Wing, NOT the Chatterbox that you are working with. I can't give you any specifics on applying it to the Chatterbox.

If you get the wiring workrd out, send me the info. I'll file it and maybe post it in the future to help someone else that will undoughtedly come up with the same idea to use the Chatterbox as you are trying to do.
 
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