In telecommunications, the term repeater has the following standard meanings:.

In the case of digital signals, the repeater is often called a regenerator because the output signal is a “regenerated signal” from the input signal.

The nature of the repeater arises from the impossibility of transmitting a signal from a transmitter to one or several receivers that are at very distant distances or from the need to overcome orographic obstacles such as mountains or mountain ranges.

Within the term repeater we can refer to different concepts regarding the type of device or installation we are talking about; We can refer to a simple device whose function is to repeat the signal it receives, as in the case of Wi-Fi repeaters or repeaters installed on the seabed to repeat the signals of transcontinental cables,[1]​ or we can also refer to the facilities or complex of facilities that repeat the radio signals "Radio (media)") and television, to which they repeat the mobile phone signals (which in this case we would call a cellular repeater) or others types of radio signals for police communications systems, emergency services or gas and electricity companies; In all of these latter cases, the term "repeater" refers to the entire set of facilities (buildings, towers, electrical and electronic equipment, antennas, etc.).

Regarding the nature of the signal with which they work, we can find three types: electrical, radioelectric or luminous signal (as in the case of fiber optic repeaters) and in all cases we continue to call them the same way.

A repeater is usually part of a transmission system. In the OSI reference model, the repeater operates at the physical level.

A subset of these are the repeaters used by radio amateurs.

Likewise, repeaters are used in point-to-point telecommunication links through radio links that operate in the microwave range "Microwaves (radiation)"), such as those used to distribute television signals between production centers and the different transmitters or those used in telecommunications networks for the transmission of telephony.[2][3]​.

Telephone repeaters consist of a receiver (earpiece) mechanically coupled to a carbon microphone. They were used before the invention of electronic amplifiers equipped with vacuum tubes.

Repeaters are often used in transcontinental and transoceanic cables because the attenuation of a signal over such distances would be completely unacceptable without them. Repeaters were formerly used in copper cables carrying electrical signals and currently in fiber optic cables carrying light.