Communications headset tester

[Luciano]

Hi Steve,

Thank you!

Yes, you are right the 10μF shouldn't be there.

The original circuit was using a 3-wire electret
microphone. A 3-wire electret microphone has a
dedicated connection for the power supply so this
is why this capacitor was there. (In the original
circuit the connection between the voltage divider
and the microphone output was not present).

About fifteen years ago I built two of them and I have
been using them everyday since as home phone intercom.

Best regards,

Luciano

[mister_e]

Good! yup 3 wire electret mic remind me something. So of course it make sense.