Phone Patch to HF radio

[SWITCHDOG]

I have a site using an R12 Definity (soon to be CM5). I have a need to send analog audio (tx & rx separately) to a HF radio system.

The control operators need to stay in the circuit with the ability to interrupt in order to meet a legal requirement. They use 8434DX phones

Any ideas on how to accomplish this? TN760E Tie Trunk to the radio as a 4 wire interface and treating it as a PCOL??