Maker Pro
Maker Pro

Interfacing an Intercom system to a PC sound card


Dan Burke

Jan 1, 1970
I'm looking for some real basic audio circuit help. I have very little
electronics knowledge.

I have a Music and Sound System Intercom unit model MC111M. I would
like to run the output signal from the Intercom system into the
line-in of a PC sound card.
I have no circuit diagrams and no clear understanding of how the
circuit works.

Anyone have any useful thoughts?

If you're qualified and charge a reasonable rate, I'd condider
contracting to have a MC111M room station modified to support an audio
out that would be suitable for a line in run.


Dan Burke

Jan 1, 1970
[email protected] (Dan Burke) wrote in message
Some more information:

The speaker is 45 ohms (I guess that's standard for a commercial
The speaker acts as the mic too (also standard).

There are 4 wires that run to the room stations. I believe 2 of them
are the audio feed (red/green). When I put a volt meter on these I get
a range of
3 to 7 millivolts (.003/.007). I believe the other 2 wires are power
and common ground (black and white). When I put a volt meter on these
I get a near constant of 10.6 volts.

The voltage seems very low compared to what I've read on this board
from messages where others have tried to interface the speaker out
from a stereo to a line-in.

Thanks for any advice.