X10 controller ranges from extremely simple to very sophisticated. The simplest X10 Controller is arranged to control four X10 Device Module(s) at four sequential addresses (1–4 or 5–8). More sophisticated X10 controller(s) can control more units and/or incorporate timers that perform preprogrammed functions at specific times each day. nits are also available that use passive infrared motion detectors or photocells to turn lights on and off based on external conditions. Finally, very sophisticated units are available that can be fully programmed or, like the X10 Firecracker, use a program running in an external computer. These systems can execute many different timed events, respond to external sensors, and execute, with the press of a single button, an entire scene, turning lights on, establishing brightness levels, and so on.