The RCX is a [Lego](/wiki/lego.html "The best known construction toy") computer, capable of controlling a number of Technic Motors and respond to inputs from a number of sensors. It houses a [MicroController](/wiki/microcontroller.html "A programmable digital controller (or "), with software, interfaces and firmware designed for [Lego](/wiki/lego.html "The best known construction toy") and their [MindStorms](/wiki/mindstorms.html "A Robotic construction toy system from Lego") brand.

RCX is an acronym for the Robot Command eXplorer.

The version 1.0 RCX has lego part number 884u. You can find it on Bricklink

The RCX comes with the Robot Inventor Sets (RIS 1.0, 1.5 and 2.0), and is shipped with an IR communication tower and windows software. As of version 2.0 - the tower is USB, before this it used 9 pin serial communications.

There are also Lego DACTA sets including the RCX for use in classrooms.

The V1.0 came with an external 9v power jack, that was later ditched. I have seen this used with other kinds of battery packs - thus allowing the bottom panel to be empty. This can lead to better even distribution of weight and other advantages.

Further RCX Projects and info

30 Cool Lego Mindstorms Project Kit: Amazing Projects You Can Build in Under an Hour

By Mario Ferrari, Giulio Ferrari

If you have the RCX then this is a must for an absolute beginner. It will give you more to do when you have finished the constructopedia.

(paid links)