For the album by the post-hardcore band Fugazi, see Repeater (album).

In telecommunication, the term repeater has the following meanings:

1. An analog device that amplifies an input signal regardless of its nature (analog or digital).
2. A digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.

(Source: from Federal Standard 1037C in support of MIL-STD-188)

A repeater is an electronic device that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. The term "repeater" originated with telegraphy and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications.

A digipeater is a portmanteau meaning "digital repeater", particularly used in amateur radio.

Telecom cables

Repeaters are often used in trans-continental and trans-oceanic cables, because the attenuation (signal loss) over such distances would be completely unacceptable without them. Repeaters are used in both copper-wire cables carrying electrical signals, and in fibre optics carrying light.

Duplex radio

In dispatching, amateur radio, and emergency services communications, repeaters are used extensively to relay radio signals across a wider area. With most emergency (and some other) dispatching systems, the repeater is synonymous with the base station, which performs both functions. This includes police, fire brigade, ambulance, taxicab, tow truck, and other services.

A duplex repeater uses two radio frequencies; an "Input" frequency, which it monitors for signals, and an "Output" frequncy, on which it retransmits the received signals at a higher power or higher altitude.

Radio repeaters are typically placed in locations which maximize their effectiveness for their intended purpose.
"Low-level" repeaters are used for local communications, and are placed at low altitude to reduce interference with other users of the same radio frequencies. Low-level systems are used for areas as large as an entire city, or as small as a single building.
"High-level" repeaters are placed on tall towers or mountaintops to maximize their area of coverage. With these systems, users with low-powered radios (such as hand-held " walkie-talkies") can communicate with each other over many miles.

In amateur radio, repeaters are typically not used as a base station by a single user or group, however they do provide other services such as an autopatch connection to a POTS/PSTN phone line for remote users. These types of repeaters typically have a squelch tone (CTCSS or PL tone) implemented, to prevent them from being keyed-up (operated) accidentally by interference from other repeaters.

Broadcasting

Repeaters are also used extensively in broadcasting, where they are known as translators or boosters. See broadcast translator for more.