What kinds of Radio Equipment are compatible with app_rpt?

The requirements are:

Ground - This is the common signal reference point between the radio and computer systems.

Transmit Audio to the Radio Transceiver - This can be via a microphone or accessory connector. It can be unprocessed or processed.

Receive Audio from the Radio Transceiver - This can be via a speaker or accessory connector. It can be flat, de-emphasized, squelched or unsquelched. An unsquelched, flat signal works best.

Transmitter Activate or PTT - This signal activates the radio transceiver's transmitter. It can be either polarity. Most Asterisk compatible interfaces are open collector outputs.

Carrier Detect or COR - This signal from the transceiver indicates to the Asterisk system that the radio is unsquelched and receiving a signal that should be handled by Asterisk. This signal is optional if a USB Radio Interface is used and connection is made directly to the receiver's unsquelched demodulated signal point (e.g. discriminator audio).