Terminator / Termination

Besides being a popular movie and a WWF wrestling star, a terminator is a device used when interconnecting equipment that has high frequency information (like video or digital data) passing between it, though termination can also be an issue at low (audio) frequencies. If you’ve ever heard an echo on a long distance phone conversation it was most likely a termination problem. In practice a terminator is often just a simple resistor or set of resistors placed at each end of a transmission line. Termination is required on video signals, SCSI chains, and other types of data transmissions. Its function is to match the impedance of the source and the load (destination), which, among other things, prevents a phenomenon known as reflections from occurring on the line. Reflections disrupt the purity of the signal in a variety of ways and can cause data drop outs and generally poor performance. A transmission line is said to be terminated if it is connected to an impedance equal to its characteristic impedance. Under these conditions a signal will “enter” the terminating impedance as if it were an infinitely long extension of the line, and no energy will be reflected.