This line follower uses three light sensors. One of them is an NXT light sensor, while the other two are RCX light sensors, attached to the NXT with custom converter cables. To make a converter cable, cut one NXT cable and one 9V style cable. Next, connect the black and white wire from the NXT cable to the two wire ends of the cut RCX cable (order is not important). You could do some nice soldering, but simple tape around each wire, and then around the completed wire does the job as well. I have used these converter cables in several other projects as well.
