The Robotics Invention System is an outstanding choice for building advanced robots. Various types of sensors can be read out using the RCX module, and three motors or other types of actuators can be driven by the pulse-width modulated outputs. However, you may sometimes want to make a model that needs more power than a single RCX module can provide. Under the motto ‘strength in unity’, it turns out that RCX modules are able to work cooperatively.After experimenting with the Robotics Invention System for a while, you will notice that the Lego system is both powerful and versatile. Still, it has its limits. Very complex robots may prove to need more active elements than can be driven or read out by a single RCX block. However, the system is flexible enough to be able to encompass additional possibilities, by using the combined forces of several modules. The demonstration robot shown in the photograph at the head of this article is a clear example of this.