Party-line / Full-duplex intercom - mixing audio signals


2013-05-21 12:19 pm
Hi All,

I'm hoping someone can help, apologies if my first post has ended up in the wrong forum. Party-line or full-duplex intercoms allow for the simultaneous transmission and reception of audio from all connected stations, i.e. effectively there is an audio 'bus' and each station takes a feed from it and routes this to its headset, and also adds a signal from its microphone that is then available to the other stations. The connecting wire can be either balanced or unbalanced.


My question is: how do you add these signals together? Do you simply connect the outputs of the output op amps/line drivers at each station together onto the wire (via some form of AC coupling [not shown in the diagram above], perhaps?).

Is that what this guy does in this circuit here?: ComClone2 Circuit Diagram