Intercom Mic (.206) Wiring

[weegidy]

I was hoping to make a little adapter to play music on my intercom system for long cross country flights. I found a .206" plug. (http://www.aircraftspruce.com/pdf/2012Individual/Cat12649.pdf No.11-00702) My plan is to solder a wire and 1/8" standard headphone plug to this. First off will this work? They sell cables that are like this for about $30 (way overpriced) so I thought I could do it myself. The only question I have is about the mic plug. It has 3 separate contacts on it. I am assuming the largest one furthest away from the tip is ground, like always, but which one of the other two (tip, and middle) contacts actually carries the audio. The mic is only a mono mic, so I doubt they both carry audio.

Here is a little diagram to help illustrate what I am hoping to do.
Stereo MP3 player -> 1/8" stereo plug -> down-mix to mono wire + ground wire -> .206" mic plug

To rephrase my question: which of the two non-ground contacts (either middle, or tip) carry the audio to the intercom system.

Thanks for your help.

 

[weegidy]

After doing some digging I found that the middle contact is the one that carries the audio, and the tip contact is for PTT. Since the mic is not amplified will I need to lower the volume of the MP3 player with an audio transformer, or resistor - or is it fine just if it it turned down low? Also, if I leave the PTT empty the audio will work, correct? Or will I need to do something to that contact?

Thanks again.