Hello all,

I'm trying to adapt a headset to be used in place of a phone handset.
The phone in question is a rather old small business style key-phone.

Most off the shelf headsets use a 3 conductor wire, speaker pos, mic
pos, and common ground.

Standard handsets have two ground conductors, isolating the speaker from
the mic.

What is needed to adapt a 4 wire handset output jack to a 3 wire
headset?

If I try to share the ground, I of course short it, and get feedback.

Any thoughts?

Thanks,
Chris

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