[maddoctor90]

"The NPN sensors do not source any voltage at all, much less 12 volts. They are the equivalent of a simple switch that is either open-circuit or closed to the power return (ground). That's basically what the Digital Sidecar was designed to connect to."

True

"The 12V optical sensors provided in the 2011 Kit of Parts will work down to at least 10.5V. Some nominally 12V sensors are spec'd to function at 9V."

Also true, but based on the original post I was assuming the sensor required above 12V to operate. Even down in the 10V operating range can still cause problems in a match when you are pulling significant enough current to drop the battery voltage below 10V.

"Can you explain why you believe <R47> applies to a pull-down resistor in a custom circuit?"

I am actually am only assuming that it is a custom circuit. I can not find anywhere in the rules where a custom circuit is defined. As I see it, the resistor would creating a circuit. Since I calculated the resistor value to use, I designed said circuit, making it "custom". Thus, why I assumed it would be a custom circuit."

I would agree with Al. The best options are to either find an NPN sensor or wire the PNP sensor through a NPN transistor before connecting it to the DS.