A repeater is an electronic device that relays a transmitted signal. It receives a signal on a specific frequency, then amplifies and rebroadcasts it. By amplifying the signal, a repeater increases the transmission range of the original signal.
Repeaters have many applications, but in computing they are most commonly used in wireless networks. For example, a Wi-Fi network in a large home may benefit from using one or more repeaters to relay the signal to different areas of the house. Homes that have brick walls or cement floors may also benefit from having a repeater relay the signal around the obstacle. Businesses often use a series of repeaters to create a single wireless network within a large building.
While repeaters all serve the same purpose, they come in many forms. Some wireless devices, often called "range extenders" are designed to be used specifically as repeaters. Other devices, such as hubs, switches, and routers can all be configured as repeaters using a software utility or web interface that controls the wireless device.
NOTE: Since repeaters only relay an incoming signal, using a router as a repeater does not make use of its signal routing capability. Therefore, it makes more sense to use a range extender as a repeater if possible.