Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.

Actual network devices that serve as repeaters usually have some other name. Active hubs, for example, are repeaters. Active hubs are sometimes also called "multiport repeaters," but more commonly they are just "hubs." Other types of "passive hubs" are not repeaters. In Wi-Fi, access points function as repeaters only when operating in so-called "repeater mode."

Repeaters are used to boost signals in coaxial and twisted pair cable and in optical fiber lines. An electrical signal in a cable gets weaker the further it travels, due to energy dissipated in conductor resistance and dielectric losses. Similarly a light signal traveling through an optical fiber suffers attenuation due to scattering and absorption. In long cable runs, repeaters are used to periodically regenerate and strengthen the signal. A network hub is one such device.

An optical communications repeater is a piece of equipment that receives an optical signal, converts that signal into an electrical one, regenerates it, and then retransmits it as an optical signal. In contrast, optical amplifiers, which amplify the light beam directly, are often used in transcontinental and submarine communications cables, because the signal loss over such distances would be unacceptable without them.

Advantages

• Makes it easy to expand a network over a large distance.
• Connection between various types of media [e.g fibre optic, UTF, coaxial cable] is possible.

Disadvantages

• Traffic cannot be filtered to ease congestion.
• A repeater cannot work across multiple network architectures.