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I have a project I've been scratching my head over for a few days.

I work a lot with 2-way radios and like to listen to music while I'm doing it. I wear an earpiece for the 2 way radio.

I want to build a circuit box I can plug the audio for the 2-way radio into along with the audio from an MP3 player and have them coming out of the same earpiece but the 2 way radio to cut out the MP3 signal when someone talks over the radio to me so I can hear it.

I thought a resistor on the radio wire but that doesn't seem to help with the problem that I have I need the music to cut out when the radio signal comes through and come back once the radio signal has stopped.

Ideally would also like to add vol controls (variable resistors) for both on the box

Anyone got any ideas or probably something horrendously simple I haven't thought of/overlooked would be greatly appreciated.

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  • \$\begingroup\$ You might want to look up audio ducking and see if that helps. \$\endgroup\$
    – JYelton
    Jun 23 '20 at 14:56
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I know that they sell analog mux ICs that can take in two signals and output one or the other. The fun part is actually knowing when to turn one or the other on right?

The music channel is the "main" channel, as in it is usually the one on. You could use a peak detector on the radio signal and feed that into a comparator to know when to toggle the mux channel. This way would allow you to tweak how long it takes for the radio to switch on (to avoid random noise and such), time to switch off after noise has stopped (to avoid switching to music mid-sentence), and the level at which you toggle. This is a two edged sword though, as you have to tweak it to make it work.

If you can, try recording some waveforms from the radio as it goes into your earpiece. You can import that into a spice program and try it out for yourself.

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