Cross band repeat.

Bring the busy (led) signal out to the mike jack on the "speach" line, assuming it does not have the voice option.

Use a transistor switch to use the signal to key the PTT line.

Run a 500k resistor from the speaker audio out to mike audio in and the volumne control at about

half way will give good levels. House the whole thing in a mike plug, no external cables. Set up the radio

for "full duplex", receiving on one band and transmit on the other. Unplug your mike and plug in the cross

band plug. This only works from one band to the other.