A couple of circuits I built back in 1998
This keys the rig for a few seconds every minute. Useful for testing without transmitting too much.
This is for connecting 2 handhelds where the PTT and microphone are on the same wire.
Both rigs must have some output which goes high when the squelch opens. I connected the squelch control to the positive battery terminal through a diode so the battery could be removed and a wire clipped on.