The wide availability of low-cost switched mains sockets with radio remote control provides a simple way to control electrical equipment, lights, etc. using a PC. Using radio not only means that we do not need a cable, but also avoids problems with electrical safety as the interface is electrically isolated from the mains supply.As USB interfaces become more widespread on PCs the serial and parallel ports are becoming less and less important. Most computers, however, still offer the ‘legacy’ ports which are available for new applications, now that devices such as printers tend to use USB. The parallel port, for example, is ideally suited for controlling electrical devices remotely. Using a simple switch interface it is possible to turn household appliances on and off under PC control.