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I use a Behringer Eurorack UB802. It has 2 mono inputs that support 1/4″ plugs or XLR with phantom power, 2 stereo line level inputs, effects loop, tape in/out, control room feed, headphone and main L/R outs. All four channels have 3 band parametric eq , L/R pan, level and effects loop send.
Sounds like a lot in a little box but I bought it at Amazon on sale for $30. For a portable mixer it sounds OK.
As for the phone-patch, KDX Radio asked if I would like to be on the next Low Power Hour show. So that I could send decent audio along with some of my station audio, I cobbled together a make-shift phone-patch.
The basic component required for that is a hybrid transformer. That device (which can be a transformer or the electronic equivalent) allows converting the 2 wire telephone line into a 4 wire connection which separates the audio into outgoing and incomming. This makes it much easier to hear the caller and your program while wearing headphones plugged into the mixer.
Since every telephone already has a hybrid circuit in it, it is simple enough to feed program audio to the handset microphone connection and the callers audio into a mixer input using the handset connection.
The handset is disconnected from the telephone and using 1:1 audio isolation transformers the mixer input and output are connected to the appropriate earphone/microphone wires of the handset cord. Careful level adjustment prevents feedback.
That’s a really low budget phone-patch. We’ll find out how it works when KDX Radio makes the CALL!