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Interfacing an iPod to the ICS

PostPosted: Wed Oct 23, 2013 1:21 pm
by fvm

I'm trying to interface an iPhone (or any other intelligent phone for that matter) into an aircraft intercom system. Here are the general parameters:

- The intercom system is mono. The earphones are 300 Ohm impedance (2 x 150). The intercom system headset power spec is 250 mW into 600 Ohm.
- The microphone is a low impedance electret (50 Ohm).

I want to be able to interface the iPhone to one headset in particular. I also want to merge the stereo outputs to a single mono signal (so I can listen to music as well). And here's the kicker: I'd like to do this with all passive components (no external power source).

I ran into a pilot the other day who has such an interface. He had it done years ago by an avionics guy, but didn't have the design specs or anything.

There are dozens of COTS devices available to interface phones to intercoms, but they are very costly, and they require power (usually batteries).

I'd like to find a DIY solution for this.

Thanks for any ideas !!!

Re: Interfacing an iPod to the ICS

PostPosted: Thu Oct 24, 2013 10:26 pm
by fvm
Another little fact that may be of importance: The iPod interface cable has four conductors, with the common being shared by both the earphones and the mic. On the aviation side, there are also four conductors, however, the earphones and mic are completely isolated from one another...