Icom OPC-478 interface
Older Icom radios use proprietary interface standard for both transceiver control and cloning. The 2-way communication is realized by 1 wire connection (+ ground), a stereo 3.5 mm plug is a connector type. One PC side the interface module is connected to standard serial port RS232 signal levels. The schematics has been publish many times everywhere (original comes from Icom), so I put it here just because of PCB design that can be usefull for someone. I have tested the module for clonning of Icom M710 maritime transceiver (I attach a cloning program as well).
OPC-478 files - circuit diagram, printed circuit board
Clonning program for Icom M710 transceiver , including default parameter files and modified parameter files (for use at HAM HF frequencies/modes).