FRS radio headset/microphone questions
Does anyone have experience making or modifying motorola FRS 2-way radio headsets with PTT and a mic?
I am trying to make a "custom" (cheap) headset using my noise canceling earbuds and any noise canceling mic i can find, to use in a motorcycle helmet. There are a few other reasons i am making my own instead of buying one, but i wont get into that.
I dont really understand the mic circuit. I took apart a cheap motorola earbud headset with a clip on mic/ptt, and it appeared to have an electret capsule. There was a board with a cap, resistor, mic element, and ptt switch. However, the motorola headset is a 2.5mm stereo 3 conductor. One speaker lead, one mic lead, and a ground (i believe). How can this power a electret mic? why the cap and resistor? or must it be dynamic?
I know a dynamic mic connected with + on the mic lead and - on ground will work, i tried it with crappy dynamic capsule i had laying around (no noise canceling though and low sensitivity, so it will not work in the helmet) using the PTT to interrupt the ground lead, but dynamic noise cancelling mic elements are hard to find. If there is a way to use an electret mic i would prefer that since i can buy them for a few bucks.