510 TMAA02-02 DTMF Microphone TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
20.5 Circuit Description
The microphone has a standard 12-key telephone keypad. When one of the
keypad keys is pressed, a DTMF tone specific to that key is generated on the
MIC_AUD line (pin 5). For the duration of the tone, the tone generator
activates the PTT, so that the user is not required to press the PTT key to
transmit each tone.
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