Do you have an old PC lying around the house which absolutely no one wants? Then you can convert it into a dedicated controller. Communicate with the real world via the parallel printer port on your PC. Simply connect printer cable from computer to Centronics connector on relay board. There are 8 relays each capable of switching 12VDC/10A or 240VAC/5A. Each relay has an LED to indicate when it is operated. We provide two sets of complete, stand-alone software to control the relays: one works under DOS so you can write your own batch files to control individual relays, the other under Windows 3.1