Repeater

In telecommunications, a repeater is a special electronic device that picks up a signal and sends it out again. This helps the signal travel farther or reach places that might be blocked, like by a hill or a building. Some repeaters send out the same signal but change how it is sent, such as using a different frequency or speed.

There are many kinds of repeaters. For example, a telephone repeater works like an amplifier in a telephone line, making the voice louder. An optical repeater uses light in an optical fiber cable to boost signals, and a radio repeater receives and sends out radio signals. A broadcast relay station is a type of repeater used for broadcast radio and television, helping to spread news and shows to larger areas.

Overview

When a message travels through a communication channel, it gets weaker. For example, when you make a telephone call through a wire, some of the power is lost. The longer the wire, the weaker the signal becomes, and you can't hear the call clearly. The same thing happens with a radio station and a receiver; the farther you are, the weaker the radio signal.

A repeater is a special electronic device that makes these signals stronger again and sends them out so they can travel farther. Because it makes the signal stronger, it needs a source of electric power. The word "repeater" started being used in the 1800s with telegraphy to describe a device that helped send telegraph messages. Today, we still use this term in telephony and data communications.

In computer networking, repeaters work with the actual signal and don't try to understand the data. They work on the physical layer, which is the first layer of the OSI model. A multiport Ethernet repeater is often called a hub.

Types

Telephone repeater

Telephone repeaters help make phone calls possible over long distances. They make the phone signal stronger so it can travel farther. Early telephone repeaters used simple parts to boost the signal. Later, they used tiny parts called transistors. Today, most long-distance calls use fiber-optic cables with special optical repeaters.

Optical communications repeater

Optical communications repeaters are used with fiber-optic cables to make sure light signals can travel far. These repeaters turn light signals into electrical signals, make them stronger, and then turn them back into light. Scientists are working on ways to make the light stronger without turning it into electricity first.

Radio repeater

Main article: Radio repeater

Radio repeaters help radio signals reach farther places, especially over hills or buildings. A radio repeater receives a weak signal and makes it stronger so it can travel farther. Some radio repeaters change the frequency of the signal. There are many kinds of radio repeaters, like those used for TV broadcasts and small ones that help cell phone signals in buildings. Radio repeaters are important because they let people talk to each other even when they are far apart or blocked by terrain.

Data handling

Repeaters come in two types, based on the data they handle.

An analog repeater works with channels that send data as an analog signal. In these signals, the strength shows the size, like in sound. These repeaters can also help send many signals at once using frequency division multiplexing and may include electronic filters to fix any changes in the signal.

A digital repeater works with channels that send data as digital signals. These are pulses that can only be one of two values, showing the binary digits 1 and 0. This type of repeater makes the signal stronger and might also fix and reshape the pulses. When it fixes the timing of the pulses, it may be called a regenerator.