Hi tanks for your reply.Electrets utilize a bias current usually supplied by the device the microphone is connected to. What is the mic connected to?
Sorry that should have read op ampHi tanks for your reply.
The microphone is connected to the telephone headset input which has an RJ 9 socket. The bias voltage I supplied from this port. if I amplify the mic with an pomp cct it works well but I need an external battery to power the circuit.
Hope this helps
The phone has a digital interface so it does not have power on it. I will test to see where the phone power is comming from and see if I can tap into it. I do know that some headset suppliers use an inline amp cable that derives the power from the microphone line. Prob with this is that the amplification is limited to what can be taken from the mic input. I would like to know how they do this as there are only 2 wires running to the mic. The audio is obviously superimposed on to the power lines and then decoupled inside the phone unit for further processing.Is the electret mic ultimately connected to a standard phone line? If so, the phone line provides the operating bias. There is plenty of voltage/current available from a standard phone-line to run the electret and a follow-0n amplifier stage.
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