Sorry for the strange question. I was wondering if anyone knew anything about the internals of the RCX mindstorms brick. Specifically, does it have a pull-down resistor (if no sensor is connected, will it read 0)?
The RCX input port has a pull-up resistor, not a pull-down (so it reads high: 1024 in raw mode). You can see reverse engineered I/O port electronics here: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=109570