Repeater
Encyclopedia
A repeater is an electronic
device that receives a
signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.
and referred to an electromechanical device used by the army to regenerate telegraph signals. Use of the term has continued in telephony
and data
communications
.
In telecommunication
, the term repeater has the following standardized meanings:
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
.
. Store and forward
digipeaters generally receive a packet radio
transmission and then retransmit it on the same frequency, unlike repeaters that receive on one and transmit on another frequency.
and submarine communications cable
s, because the attenuation
(signal loss) over such distances would be unacceptable without them. Repeaters are used in both copper
-wire
cables carrying electrical signals, and in fiber optics carrying light
.
Repeaters are used in radio communication services. Radio repeaters often transmit and receive on different frequencies. A special subgroup of those repeaters is those used in amateur radio
.
Repeaters are also used extensively in broadcasting
, where they are known as translators, boosters or TV relay transmitters.
When providing a point-to-point telecom link using radio beyond line of sight, one uses repeaters in a microwave radio relay. A reflector, often on a mountaintop, that relays such signals around an obstacle, is called a passive repeater
or Passive Radio Link Deflection. A microwave repeater in a communications satellite
is called a transponder
.
In optical communications the term repeater is used to describe a piece of equipment that receives an optical signal, converts that signal into an electrical one, regenerates it, and then retransmits an optical signal. Since such a device converts the optical signal into an electrical one, and then back to an optical signal, they are often known as Optical-Electrical-Optical
(OEO) repeaters.
Before the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. The invention of the audion tube
made transcontinental telephony practical. In the 1930s vacuum tube
repeaters using hybrid coil
s became commonplace, allowing the use of thinner wires. In the 1950s negative impedance
gain devices were more popular, and a transistor
ized version called the E6 repeater was the final major type used in the Bell System
before the low cost of digital transmission made all voiceband
repeaters obsolete. Frequency frogging
repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century.
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
device that receives a
signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.
Description
The term "repeater" originated with telegraphyTelegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
and referred to an electromechanical device used by the army to regenerate telegraph signals. Use of the term has continued in telephony
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....
and data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
communications
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
.
In telecommunication
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
, the term repeater has the following standardized meanings:
- An analog deviceInformation applianceIn general terms, an information appliance or information device is any machine or device that is usable for the purposes of computing, telecommunicating, reproducing, and presenting encoded information in myriad forms and applications....
that amplifiesAmplifierGenerally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
an input signal regardless of its nature (analog or digitalDigitalA digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
). - A digitalDigitalA digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmissionTransmission (telecommunications)Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
.
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
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
.
Digipeater
A "digipeater" is a blend meaning "digital repeater", particularly used in amateur radioAmateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
. Store and forward
Store and forward
Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in a networking context, verifies the integrity of...
digipeaters generally receive a packet radio
Packet radio
Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated...
transmission and then retransmit it on the same frequency, unlike repeaters that receive on one and transmit on another frequency.
Usage
Repeaters are often used in transcontinentalL-carrier
SystemYearFrequencyCoax per cableDistance between repeatersVoice circuits per coax tubeL-119413 MHz48 miles600L-21942840 kHz416 miles360L-319508 MHz84 miles1,860L-4196717 MHz202 miles3,600L-5197257 MHz221 mile10,800L-5E197566 MHz221 mile13,200...
and submarine communications cable
Submarine communications cable
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean....
s, because the attenuation
Attenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
(signal loss) over such distances would be unacceptable without them. Repeaters are used in both copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
-wire
Wire
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...
cables carrying electrical signals, and in fiber optics carrying light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
.
Repeaters are used in radio communication services. Radio repeaters often transmit and receive on different frequencies. A special subgroup of those repeaters is those used in amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
.
Repeaters are also used extensively in broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
, where they are known as translators, boosters or TV relay transmitters.
When providing a point-to-point telecom link using radio beyond line of sight, one uses repeaters in a microwave radio relay. A reflector, often on a mountaintop, that relays such signals around an obstacle, is called a passive repeater
Passive repeater
A passive radio link deflection, or passive repeater is a plant for the implementation of a microwave link, in which because of an obstacle in the signal path no direct line of sight microwave link is possible...
or Passive Radio Link Deflection. A microwave repeater in a communications satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
is called a transponder
Transponder (Satellite communications)
A communications satellite’s transponder, is the series of interconnected units which form a communications channel between the receiving and the transmitting antennas .A transponder is typically composed of:...
.
In optical communications the term repeater is used to describe a piece of equipment that receives an optical signal, converts that signal into an electrical one, regenerates it, and then retransmits an optical signal. Since such a device converts the optical signal into an electrical one, and then back to an optical signal, they are often known as Optical-Electrical-Optical
Optical communications repeater
An optical communications repeater is used in a fiber-optic communications system to regenerate an optical signal by converting it to an electrical signal, processing that electrical signal and then retransmitting an optical signal...
(OEO) repeaters.
Before the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. The invention of the audion tube
Audion tube
The Audion is an electronic amplifying vacuum tube invented by Lee De Forest in 1906. It was the forerunner of the triode, in which the current from the filament to the plate was controlled by a third element, the grid...
made transcontinental telephony practical. In the 1930s vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
repeaters using hybrid coil
Hybrid coil
A hybrid coil is a transformer that has three windings, and which is designed to be configured as a circuit having four branches, that are conjugate in pairs....
s became commonplace, allowing the use of thinner wires. In the 1950s negative impedance
Negative resistance
Negative resistance is a property of some electric circuits where an increase in the current entering a port results in a decreased voltage across the same port. This is in contrast to a simple ohmic resistor, which exhibits an increase in voltage under the same conditions. Negative resistors are...
gain devices were more popular, and a transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
ized version called the E6 repeater was the final major type used in the Bell System
Bell System
The Bell System was the American Bell Telephone Company and then, subsequently, AT&T led system which provided telephone services to much of the United States and Canada from 1877 to 1984, at various times as a monopoly. In 1984, the company was broken up into separate companies, by a U.S...
before the low cost of digital transmission made all voiceband
Voiceband
In electronics, voiceband means the typical human hearing frequency range that is from 20 Hz to 20 kHz. In telephony, it means the frequency range normally transmitted by a telephone line, generally about 200–3600 Hz. Frequency-division multiplexing in telephony normally uses...
repeaters obsolete. Frequency frogging
Frequency frogging
In telecommunication, the term frequency frogging has the following meanings:# The interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce crosstalk, and to correct for a high frequency response slope in the...
repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century.
External links
- Repeater Electrical Engineer Standard Dictionary