Thanks Alain for the suggestion. I will look and see what I can learn from there.

Current plan is to use DT-Ints to capture and measure the width of the incoming pulses to determine weather they are short (58uS :"1") or long (100uS: "0") or standard AC power (16.7mS) and generate a level of 1 or 0 if it is data. If Std. AC I can jump to a fall-back and pick one of a few basic modes by cycling the power. The data pulses, once decoded, could be simply fed into the USART.