Batboard

Im making a repeater to cross band from UHF into a trunking talkgroup. The only problem is on the trunking maxtrac It only gives me the option for Null Output Low on Pin 8. The uhf passes to 800 just fine but I cant get the 800 to pass back thru the UHF. Are there any jumpers inside or is there something else I am missing? (these are both 16 pin)

My two bits worth:
The factory RICK box uses a VOX circuit.
You may want to try one of these.

The "16 pin" control board has two versions, 4 channel and 16 channel.
The 4 channel has only a COR output. I do not what this does on a trunking radio.
The 16 channel board has several programmable pins.

If you are building an interface you will need to know which board you are using.