Repeater
A device that receives and retransmits a signal to extend range.
A repeater is an electronic device that picks up a signal and sends it out again. Its purpose is to extend a transmission, allowing it to travel farther or reach past an obstruction. Some repeaters retransmit the exact same signal but change how it is sent, such as using a different frequency or baud rate.
When a signal travels through a communication channel, it loses power over distance. In a telephone wire, some electrical energy turns into heat in the copper, weakening the audio signal. With a long enough wire, the call becomes inaudible. Similarly, a radio signal grows weaker the farther it travels from the transmitter. A repeater boosts the signal’s power and retransmits it, which requires its own source of electric power.
The term "repeater" first appeared in 19th-century telegraphy, referring to an electromechanical relay that regenerated telegraph signals. The word later carried over into telephony and data communications. In computer networking, repeaters work with the raw physical signal without interpreting the data, so they operate at the physical layer (layer one) of the OSI model. A multiport Ethernet repeater is commonly called a hub.
There are several types of repeaters. A telephone repeater amplifies signals on a telephone line. Land-line repeaters are often used on trunk lines for long-distance calls. On an analog two-wire line, the repeater is a transistor amplifier that draws power from a DC source to boost the alternating current audio signal. Because telephone lines are bidirectional, the repeater must amplify signals in both directions without causing feedback, which makes the design complex. Telephone repeaters were the first type of repeater and among the earliest applications of amplification. Their development between 1900 and 1915 made long-distance phone service possible. Before electronic amplifiers, mechanically coupled carbon microphones served as amplifiers. After the turn of the 20th century, negative resistance mercury lamps were used. The invention of audion tube repeaters around 1916 enabled transcontinental telephony. By the 1930s, vacuum tube repeaters with hybrid coils allowed thinner wires. By 1933, long-distance carrier lines had a repeater every 25 miles over 850-mile routes.
- First proposal
- 1898 by Johann Mattausch
- First functioning system
- 1899 by Emile Guarini-Foresio
- Osi model layer
- Physical layer (layer 1)
- Typical spacing in 1930s long-distance c
- Every 25 miles over distances of 850 miles
Lore & Background
The term 'repeater' originated with telegraphy in the 19th century, referring to an electromechanical device (a relay) used to regenerate telegraph signals. The history of radio relay repeaters began in 1898 with a publication by Johann Mattausch, though his proposal was primitive and not suitable for use. The first relay system with radio repeaters that actually functioned was invented in 1899 by Emile Guarini-Foresio.
Telephone repeaters were the first type of repeater and were some of the first applications of amplification. Before electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. After the turn of the 20th century, negative resistance mercury lamps were found to amplify and were used. The invention of audion tube repeaters around 1916 made transcontinental telephony practical. In the 1930s, vacuum tube repeaters using hybrid coils became commonplace, allowing the use of thinner wires. In the 1950s, negative impedance gain devices were more popular, and a transistorized version called the E6 repeater was the final major type used in the Bell System before digital transmission made all voiceband repeaters obsolete.
Radio repeaters improve communication coverage in systems using frequencies that typically have line-of-sight propagation. Without a repeater, these systems are limited in range by the curvature of the Earth and the blocking effect of terrain or high buildings. A repeater on a hilltop or tall building can allow stations that are out of each other's line-of-sight range to communicate reliably. Radio repeaters may also allow translation from one set of radio frequencies to another, for example to allow two different public service agencies to interoperate.
Reader's Guide
The repeater has been fundamental to extending communication over long distances and around obstacles. In telephony, the development of telephone repeaters between 1900 and 1915 made long-distance phone service possible, and by 1933, long-distance carrier telephony lines had a repeater every 25 miles over distances of 850 miles. In radio, repeaters allow stations that are out of line-of-sight range to communicate reliably by placing a repeater on a hilltop or tall building. In computer networking, repeaters operate on the physical layer of the OSI model, working with the actual physical signal without interpreting the data being transmitted; a multiport Ethernet repeater is usually called a hub. Various specialized types have emerged: broadcast relay stations extend coverage of radio or television broadcasting; microwave relay stations transmit telephone calls, television programs, and computer data over continent-wide areas; cellular repeaters boost cell phone reception in limited areas; digipeaters perform store-and-forward functions in packet radio networks; and amateur radio repeaters enable two-way communication across areas difficult for point-to-point VHF and UHF. The repeater remains a core component in both legacy and modern communication systems, adapting from electromechanical relays to optical amplifiers that amplify light directly without converting it to an electrical signal first.
Did You Know?
- The first functioning radio relay system was invented in 1899 by Emile Guarini-Foresio.
- A passive repeater is a microwave relay that simply consists of a flat metal surface to reflect the microwave beam in another direction.
Frequently Asked Questions
What is a repeater in radio electronics?
A repeater is a small electronic unit that catches a weakening transmission and broadcasts it again, effectively giving the signal a second life so it can travel further or get past obstacles.
Who first proposed the repeater concept?
The idea was first put forward by Johann Mattausch back in 1898, though it took another year before anyone managed to build a working system.
Who built the first functioning repeater?
Emile Guarini-Foresio is credited with constructing the first working repeater in 1899, turning the earlier theoretical proposal into a device that actually operated.
Which OSI model layer does a repeater operate on?
A repeater sits at the Physical layer, which is layer 1 of the OSI model, because it simply amplifies and re-sends raw signal data without interpreting any higher-level protocol.
How were repeaters spaced in early long-distance telephone cables?
In the 1930s, repeaters were placed roughly every 25 miles along cables that stretched up to 850 miles, compensating for the signal loss that accumulated in the copper wire.
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