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26-436: A data link is a means of connecting one location to another for the purpose of transmitting and receiving digital information ( data communication ). It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver (two pieces of data terminal equipment ) and the interconnecting data telecommunication circuit . These are governed by a link protocol enabling digital data to be transferred from

52-506: A DS-1 , or radio links. The consoles multiplex transmit commands onto remote control circuits. Some system configurations require duplex, or four wire, audio paths from the base station to the console. Others require only a two-wire or half duplex link. Interference could be defined as receiving any signal other than from a radio in your own system. To avoid interference from users on the same channel, or interference from nearby strong signals on another channel, professional base stations use

78-464: A network-layer protocol like IP . Unlike broadcast links, there is no mechanism to efficiently send a single message to all other nodes without copying and retransmitting the message. A point-to-multipoint link (or simply a multipoint ) is a specific type of multipoint link which consists of a central connection endpoint (CE) that is connected to multiple peripheral CEs. All of the peripheral CEs receive any transmission of data that originates from

104-659: A combination of: Base stations are sometimes called control or fixed stations in US Federal Communications Commission licensing. These terms are defined in regulations inside Part 90 of the commissions regulations. In US licensing jargon, types of base stations include: In amateur radio , a base station also communicates with mobile rigs but for hobby or family communications. Amateur systems sometimes serve as dispatch radio systems during disasters, search and rescue mobilizations, or other emergencies. An Australian UHF CB base station

130-520: A data source to a data sink . There are at least three types of basic data-link configurations that can be conceived of and used: In civil aviation , a data-link system (known as Controller Pilot Data Link Communications ) is used to send information between aircraft and air traffic controllers for example when an aircraft is too far from the ATC to make voice radio communication and radar observations possible. Such systems are used for aircraft crossing

156-445: A downlink (satellite to mobile user). The reverse link (sometimes called a return channel ) is the link from a mobile user to a fixed base station. If the link includes a communications relay satellite , the reverse link will consist of both an uplink (mobile station to satellite) and a downlink (satellite to base station) which together constitute a half hop . Base station Base station (or base radio station )

182-581: A low-power transmitter and wireless router . In radio communications, a base station is a wireless communications station installed at a fixed location and used to communicate as part of one of the following: Base stations use RF power amplifiers ( radio-frequency power amplifiers) to transmit and receive signals. The most common RF power amplifiers are metal–oxide–semiconductor field-effect transistors (MOSFETs), particularly LDMOS ( power MOSFET ) RF amplifiers. RF LDMOS amplifiers replaced RF bipolar transistor amplifiers in most base stations during

208-462: A number of other devices to one another and/or to a wider area. In mobile telephony, it provides the connection between mobile phones and the wider telephone network . In a computer network , it is a transceiver acting as a switch for computers in the network, possibly connecting them to a/another local area network and/or the Internet . In traditional wireless communications, it can refer to

234-550: A primary selected channel is routed to the select speaker and to a headset. Each channel has a busy light which flashes when someone talks on the associated channel. Base stations can be local controlled or remote controlled. Local controlled base stations are operated by front panel controls on the base station cabinet. Remote control base stations can be operated over tone- or DC-remote circuits. The dispatch point console and remote base station are connected by leased private line telephone circuits, (sometimes called RTO circuit s),

260-551: A properly designed dispatch center with several staff members, this allows each dispatcher to communicate simultaneously, independently of one another, on a different channel as necessary. For example, a taxi company dispatch center may have one base station on a high-rise building in Boston and another on a different channel in Providence . Each taxi dispatcher could communicate with taxis in either Boston or Providence by selecting

286-514: A single internal intercom station, a radio path between two points, etc.). Broadcast links connect two or more nodes and support broadcast transmission , where one node can transmit so that all other nodes can receive the same transmission. Classic Ethernet is an example. Also known as a multidrop link, a multipoint link is a link that connects two or more nodes. Also known as general topology networks, these include ATM and Frame Relay links, as well as X.25 networks when used as links for

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312-434: Is another example of part of a system used for hobby or family communications. Wireless telephone differ from two-way radios in that: A wireless telephone base station communicates with a mobile or hand-held phone. For example, in a wireless telephone system, the signals from one or more mobile telephones in an area are received at a nearby base station, which then connects the call to the land-line network. Other equipment

338-471: Is involved depending on the system architecture. Mobile telephone provider networks, such as European GSM networks, may involve carrier , microwave radio , and switching facilities to connect the call. In the case of a portable phone such as a US cordless phone, the connection is directly connected to a wired land line. While low levels of radio-frequency power are usually considered to have negligible effects on health, national and local regulations restrict

364-430: Is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects." The consensus of the scientific community is that the power from these mobile phone base station antennas is too low to produce health hazards as long as people are kept away from direct access to the antennas. However, current international exposure guidelines ( ICNIRP ) are based largely on

390-438: Is widely used in computer networking to refer to the communications facilities that connect nodes of a network. Sometimes the communications facilities that provide the communication channel that constitutes a link are also included in the definition of link . A point-to-point link is a dedicated link that connects exactly two communication facilities (e.g., two nodes of a network, an intercom station at an entryway with

416-513: Is – according to the International Telecommunication Union 's (ITU) Radio Regulations (RR) – a " land station in the land mobile service ." The term is used in the context of mobile telephony , wireless computer networking and other wireless communications and in land surveying . In surveying, it is a GPS receiver at a known position, while in wireless communications it is a transceiver connecting

442-523: The Atlantic and Pacific oceans. One such system, used by Nav Canada and NATS over the North Atlantic, uses a five-digit data link sequence number confirmed between air traffic control and the pilots of the aircraft before the aircraft proceeds to cross the ocean. This system uses the aircraft's flight management computer to send location, speed and altitude information about the aircraft to

468-415: The 1990s, leading to the wireless revolution . In professional two-way radio systems, a base station is used to maintain contact with a dispatch fleet of hand-held or mobile radios, and/or to activate one-way paging receivers. The base station is one end of a communications link. The other end is a movable vehicle-mounted radio or walkie-talkie. Examples of base station uses in two-way radio include

494-589: The ATC. ATC can then send messages to the aircraft regarding any necessary change of course. In unmanned aircraft , land vehicles, boats, and spacecraft, a two-way ( full-duplex or half-duplex ) data-link is used to send control signals , and to receive telemetry . Telecommunications link A telecommunications link is generally based on one of several types of information transmission paths such as those provided by communication satellites , terrestrial radio communications infrastructure and computer networks to connect two or more points. The term link

520-460: The central CE while any transmission of data that originates from any of the peripheral CEs is only received by the central CE. Links are often referred to by terms that refer to the ownership or accessibility of the link. A forward link is the link from a fixed location (e.g., a base station ) to a mobile user. If the link includes a communications relay satellite , the forward link will consist of both an uplink (base station to satellite) and

546-400: The design of base stations to limit exposure to electromagnetic fields . Technical measures to limit exposure include restricting the radio frequency power emitted by the station, elevating the antenna above ground level, changes to the antenna pattern, and barriers to foot or road traffic. For typical base stations, significant electromagnetic energy is only emitted at the antenna, not along

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572-415: The dispatch of tow trucks and taxicabs . Professional base station radios are often one channel. In lightly used base stations, a multi-channel unit may be employed. In heavily used systems, the capability for additional channels, where needed, is accomplished by installing an additional base station for each channel. Each base station appears as a single channel on the dispatch center control console. In

598-449: The hub of a dispatch fleet such as a taxi or delivery fleet, the base of a TETRA network as used by government and emergency services or a CB shack . In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS receivers. This correction data allows propagation and other effects to be corrected out of

624-495: The length of the antenna tower. Because mobile phones and their base stations are two-way radios, they produce radio-frequency ( RF ) radiation in order to communicate, exposing people near them to RF radiation giving concerns about mobile phone radiation and health . Hand-held mobile telephones are relatively low power so the RF radiation exposures from them are generally low. The World Health Organization has concluded that "there

650-419: The position data obtained by the mobile stations, which gives greatly increased location precision and accuracy over the results obtained by uncorrected GPS receivers. In the area of wireless computer networking, a base station is a radio receiver/transmitter that serves as the hub of the local wireless network, and may also be the gateway between a wired network and the wireless network. It typically consists of

676-435: The respective base station on his or her console. In dispatching centers it is common for eight or more radio base stations to be connected to a single dispatching console. Dispatching personnel can tell which channel a message is being received on by a combination of local protocol, unit identifiers, volume settings, and busy indicator lights. A typical console has two speakers identified as select and unselect . Audio from

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