Repeater
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.
This article is about the electronic device. For other uses, see Repeater (disambiguation).
There are several different types of repeaters; a telephone repeater is an amplifier in a telephone line, an optical repeater is an optoelectronic circuit that amplifies the light beam in an optical fiber cable; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal.
A broadcast relay station is a repeater used in broadcast radio and television.
Overview[edit]
When an information-bearing signal passes through a communication channel, it is progressively degraded due to loss of power. For example, when a telephone call passes through a wire telephone line, some of the power in the electric current which represents the audio signal is dissipated as heat in the resistance of the copper wire. The longer the wire, the more power is lost, and the smaller the amplitude of the signal at the far end. So with a long enough wire the call will not be audible at the other end. Similarly, the greater the distance between a radio station and a receiver, the weaker the radio signal, and the poorer the reception. A repeater is an electronic device in a communication channel that increases the power of a signal and retransmits it, allowing it to travel further. Since it amplifies the signal, it requires a source of electric power.
The term "repeater" originated with telegraphy in the 19th century, and referred to an electromechanical device (a relay) used to regenerate telegraph signals.[1][2]
Use of the term has continued in telephony and data communications.
In computer networking, because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on the physical layer, the first layer of the OSI model; a multiport Ethernet repeater is usually called a hub.