Thanks SLL. I sent an email and sure enough, Scott promptly responded. For those interested, it is a photo input (so it is polarity sensitive, but no inductive spike to worry about from a coil) and is current limited. I'm going with a 1K resistor in series in case I short the connector.

I think my 7100 should be showing up soon. It will be joining its big brother (755) to triamp the front 3 speakers. I didn't spring for express shipping, so its going ground, but I think I may have been nearly the first order. I ordered last friday morning.