I am looking for any guidance on interfacing an RTCM to a TKR-750. In particular: 1) should I use TA or TD for feeding in the transmit audio (I am using TD) 2) how should I configure the channel ('duplex'?) 3) what about other settings like PTT priority (currently local mic, external ptt, repeat ptt) I initially used channel mode 'repeat' which is not right because then you get local repeat mixed with the transmit audio coming from the RTCM (slightly delayed). I switched to duplex mode and now I am PTT but transmit audio. Form my contribution, I can offer a solution to the level problem interfacing the CTCSS decode (TOR) to the CTCSS line on the RTCM. I used an NPN transistor and a voltage divider (15k, 5k) to ground fed by the TOR (active high) from the Kenwood. This works nicely. -Doug- KD7DK