Using a GTX mobile for VoIP link to our 900 rptr and have done the COS hack, but need de-emph / sq gated audio for the path. I suppose there is no internal jumper for de-emph audio on the flat audio out of the 16 pin accessory like in the maxtracs. I did see a post where one user hjacked the speaker audio but I would have thought that the amp needs to float and not tied to ground. There does appear to be handset audio on the mic jack, but is volume control dependant.
I suppose I could de-emph the flat audio on the 16 pin accessory and bring an extra NPN out to mute it... but wondering if anyone has picked off a better tap for de-emph / sp muted audio off the board... that would hopefully gate on PL decode as well. Without a schematic I am firing blind here.
Danny KD4RAA
Need de-emph audio from GTX mobile
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jackhackett
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Looking at the schematic it looks like detected audio(DET_AUDIO) goes into an ASFIC chip, flat audio(FLT_RX_AUDIO) and receive audio(RX_AUDIO) come out of it. The flat audio goes through a buffer to the acc. jack, and the receive audio goes through a small amp to the handset and also to the audio PA. Doesn't look like anything useful there.
There is also a FILTERED_AUDIO output from the ASFIC, which is filtered de-emphasised audio taken before the volume control, it doesn't say if it's muted or not. This goes to the hear clear through a capacitor, so it should be possible to pick off this signal at the cap.
There is also a FILTERED_AUDIO output from the ASFIC, which is filtered de-emphasised audio taken before the volume control, it doesn't say if it's muted or not. This goes to the hear clear through a capacitor, so it should be possible to pick off this signal at the cap.