If you experience issues when interfacing a TP3200 to a 1225, I recently resolved this on a repeater I was interfacing one of these to. The COS line coming from the 1225 16 pin connector is not changing state and being held “high” all the time. To fix this, add a 150-470 ohm resistor from the COS pin to ground at either connector or internally in the TP3200. The TP3200 has an internal pull up resistor and the programmable COS pin coming out of the radio is pulled high by this resistor when the pin is supposed to be in an “off” or 0 state. Adding the resistor pulls the pin low when it is supposed to be low and allows the TP3200 to correctly detect the COS as programmed.
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