中继器
维基百科，自由的百科全书
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在长途通信领域，中继器有如下含义:
- 一个将输入信号增强放大的模拟设备，而不考虑输入信号种类（是模拟的还是数字的）。
- A digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.
(Source: from Federal Standard 1037C in support of MIL-STD-188)
A repeater is an 电子 device that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. The term "repeater" originated with telegraphy and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications.
A digipeater is a portmanteau meaning "digital repeater", particularly used in amateur radio.
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[编辑] 通信线缆
Repeaters are often used in trans-continental and trans-oceanic cables, because the attenuation (signal loss) over such distances would be completely unacceptable without them. Repeaters are used in both copper-wire cables carrying electrical signals, and in fibre optics carrying light.
[编辑] Duplex radio
In dispatching, amateur radio, and emergency services communications, repeaters are used extensively to relay radio signals across a wider area. With most emergency (and some other) dispatching systems, the repeater is synonymous with the base station, which performs both functions. This includes police, fire brigade, ambulance, taxicab, tow truck, and other services. The civilian GMRS service in the United States and UHF CB service in Australia also use repeaters in much the same fashion as amateur radio operators do; however, the Canadian GMRS service is an expansion of the Family Radio Service and is designed to operate simplex-only.
A duplex repeater uses two radio frequencies; an "Input" frequency, which it monitors for signals, and an "Output" frequncy, on which it retransmits the received signals at a higher power or higher altitude.
Radio repeaters are typically placed in locations which maximize their effectiveness for their intended purpose.
"Low-level" repeaters are used for local communications, and are placed at low altitude to reduce interference with other users of the same radio frequencies. Low-level systems are used for areas as large as an entire city, or as small as a single building.
"High-level" repeaters are placed on tall towers or mountaintops to maximize their area of coverage. With these systems, users with low-powered radios (such as hand-held " walkie-talkies") can communicate with each other over many miles.
[编辑] Amateur radio
In amateur radio, repeaters are typically maintained by individual hobbyists or local groups of amateur radio operators such as the KR9RK Lakeshore Repeater Association. Many repeaters are provided openly to other amateur radio operators and typically not used as a remote base station by a single user or group. In some areas multiple repeaters are linked together to form a wide-coverage network.
It is considered good practice to help support a repeater you use frequently. Services provided by a repeater may include an autopatch connection to a POTS/PSTN phone line to allow users to make telephone calls from their radios. These advanced services may be limited to members of the group or club that maintains the repeater. Many amateur radio repeaters typically have a squelch tone (CTCSS or PL tone) implemented to prevent them from being keyed-up (operated) accidentally by interference from other repeaters.
In many communities, the repeater has become the on-the-air gathering spot for the local Amateur radio community. Local public service nets may be heard on these systems and many are employed by weather spotters. In an emergency or a disaster a repeater can sometimes help to provide needed communications between areas that could not otherwise communicate.
Repeaters may also be linked together or connected to over the internet using voice over IP (VoIP). Echolink allows hams with computers can connect to repeaters anywhere around the world and and The Internet Radio Linking Project (IRLP) allows for direct repeater linking. In addition, communications satellites called OSCARs have been launched with the specific purpose of operating as spaceborne amateur repeaters.
[编辑] 广播
Repeaters are also used extensively in broadcasting, where they are known as translators or boosters. See broadcast translator for more.
