Multiplexors

The RCX, which is used to control robotic arm, has a major limitation: It has only three outputs.  Obviously, for an arm, you need at least four: height of the arm and the forearm, rotation of the base, and open/close the hand.

I call "Multiplexors" devices that are meant to control two or more motors using a smaller number of output of the RCX.

This figure illustrates a 1-to-2 multiplexor:

These devices are quite important given the very limited number of outputs on the RCX (only three). Most realistic application you'll want to realize is likely to have more than that.

In the following, I describe two methods to implement multiplexors:

	The 1-to-2 multiplexor: It controls 2 motors using only one motor and thus only one port of the RCX.
	The 2-to-7 multiplexor: It can control 7 motors using 2 motors connected to 2 ports of the RCX.