I have an extra 512 (precursor to the G12) and changed out the DIN connector to 1/8" TRS connector for the 218 - works like a champ. It's a 3wire system. 12V, GND, SIGNAL. I would imagine you might be able to find another IR Receiver manufacturer whose system works 3wire, but I don't know who.

John

Main system: Cable, Apple TV, HD621, G68D, AC11, 218, DSP7200SE (L+R), DSP3200 (L+R Rear)
2nd system: Cable, Apple TV, MC200, HD621, 568.2, M3100 (L+R)