Also known as a surge suppressor, a device that protects sensitive data communications equipment (DCE) and data terminal equipment (DTE) from sudden rises in power line voltages called surges or spikes.
Surges occur only with copper cabling such as twisted-pair cabling or coaxial cabling - they do not occur with fiber-optic cabling, which is one advantage of using this more expensive type of cabling for networking applications. Surge protectors use various technologies for absorbing or deflecting unwanted electrical current, including avalanche diodes, metal oxide varistors, and chokes or filters. One of the best electrical protection methods, especially for copper wiring runs between different buildings, is to use opto isolators, which convert electrical signals to light and then back again, thus providing true electrical isolation between the connected buildings. However, opto isolation in itself does not provide surge protection; this is the responsibility of the other components described, the most common component being the various types of diodes.
Surge protectors for computer networking come in two main types: