Question:

What is the difference between a 3-pin XLR connector wired for balanced audio input / output and a 3-pin XLR connector wired to support a Clear-Com party-line system?

I need to connect the party-line audio feed to an audio mixer input.  Is this possible?

Answer:

The audio connections of both systems are different, the balanced audio feed is considered a 4-wire connection that doesn't use a Vdc component on any of the 3-pins of the XLR connector.

A 3-pin XLR wired for Clear-Com intercom audio is considered an unbalanced 2-wire connection that uses a +30Vdc on one of the XLR pins to power various intercom stations, beltpacks and interfaces.

The two disciplines are not compatible and in order to join them together an interface is required to bridge the unbalanced and balanced audio paths together. 

Balanced 3-pin XLR audio pinouts (4-wire)











Clear-Com unbalanced intercom 3-pin XLR pinouts (2-wire)















Clear-Com manufacturers several different 2-wire to 4-wire interfaces for applications that require injecting intercom audio to a third party audio device such as a mixer, public address system and or a recording device. 
Clear-Com interfaces:
EF-701M - Converts one channel of PL audio to balanced audio including direct connection to a Matrix frame or fiber optic devices
IF4W4 - Converts 4 channels of PL audio to balanced audio (for TV cameras, 2-way radios)
AC-701 - Converts one channel of PL audio to other 2-wire, 3-wire, 4-wire or telephone lines