I just scored some interesting goodies over the weekend:

An FL-44A filter;
An EX-309 Interface (parallel I/O; more on this later);
Two (count 'em) IC-EX1 "expansion terminals".

Icom incorporated a method of controlling its transceivers via PC serial port and CI-V interface starting with the IC-751...but a parallel data exchange mechanism existed within their architecture as far back as the IC-720/R70 line. To that end, an IC-7072 'transceive controller' was offered as an option. It allowed the R70's VFO to control the 720 by virtue of data lines present in the 24p accessory connector which resides on the back panel of each rig.

Examining the EX-309 / IC-7072 / IC-720 / R70 schematics, I think that I can adapt the '309 and the IC-745's accessory connector to accommodate a '7072 and an attendant R70 in master-slave mode...:chin: