Just hook them to the Analog Port. Parallax also sells some, I don't know how much. But , these will work fine. It will give you a voltage reading between 0 and 5 volts. D.J. would have to tell you but I guess they would also work on the digital port for a True/False reading. But, you would probably have to write a little code for them. They will keep you on line, or keep you from falling down the stairs.

P.S. my humble 2Cents. Verify with D.J. before you act.

Mel

thx moviemaker