Transient-voltage surge suppression (TVSS) is necessary for most electronic and computer devices exposed to telecommunications or power lines. The design of effective TVSS devices is discussed in the paper. A complete TVSS system consists of shunt protectors on the input and output. Other components may include the input shunted with a capacitor and an inductor placed inline. The grounds are isolated on the input and output. For low energy systems, an MOV is often the only device used. This may be effective if it is adequately sized and has not deteriorated. For circuits exposed to higher energy and for power circuits, another primary arrester should be included. The fastest system uses avalanche diodes with a primary arrester to dissipate the larger energy. For adequate protection, three conditions are critical. A semiconductor device is required. A high-energy primary arrester is used in conjunction. The configuration is arranged for all possible scenarios. Finally, protection will generally be inappropriate without a very effective ground grid.