Well here's the scoop on the GM300's, M120's and M10's. The sheet says there is a difference between the 8 and 16 channel units. We'll try to describe both. COR active low RUIndicator follows tone if used. The plug that goes into the radio is as follows.
Top row is odd numbers, bottom row is even.
Also, the 5 pin radios will not do this because you can't get COS and PTT outputs.