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Inbroadcasting andradio communications, acall sign (also known as acall name orcall letters—and historically as acall signal—or abbreviated as acall) is aunique identifier for atransmitter station. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or evencryptographicallyencoded to disguise a station's identity.
The use of call signs as unique identifiers dates to the landlinerailroadtelegraph system. Because there was only onetelegraph line linking allrailroad stations, there needed to be a way toaddress each one when sending atelegram. In order to save time, two-letter identifiers were adopted for this purpose. This pattern continued inradiotelegraph operation;radio companies initially assigned two-letter identifiers tocoastal stations andstations on board ships at sea. These were not globally unique, so a one-letter company identifier (for instance, 'M' and two letters as aMarconi station) was later added. By 1912, the need to quickly identify stations operated by multiple companies in multiple nations required aninternational standard; anITU prefix would be used to identify a country, and the rest of the call sign an individual station in that country.[1]
Merchant and naval vessels are assigned call signs by their national licensing authorities. In the case of states such asLiberia orPanama, which areflags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters (for example, 3LXY, and sometimes followed by a number, e.g. 3LXY2). United States merchant vessels are given call signs beginning with the letters "W" or "K" while US naval ships are assigned call signs beginning with "N". Originally, both ships and broadcast stations were assigned call signs in this series consisting of three or four letters. Ships equipped with Morse code radiotelegraphy, or life boat radio sets, aviation ground stations, broadcast stations were given four-letter call signs. Maritime coast stations on high frequency (both radiotelegraphy and radiotelephony) were assigned three-letter call signs. As demand for bothmarine radio and broadcast call signs grew, gradually American-flagged vessels with radiotelephony only were given longer call signs with mixed letters and numbers.
Leisure craft with VHF radios may not be assigned call signs, in which case the name of the vessel is used instead. Ships in the US still wishing to have a radio license are underFCC class SA: "Ship recreational or voluntarily equipped." Those calls follow the land mobile format of the initial letter K or W followed by one or two letters followed by three or four numbers (such as KX0983 or WXX0029).U.S. Coast Guard small boats have a number that is shown on both bows (i.e. port and starboard) in which the first two digits indicate the nominal length of the boat in feet. For example, Coast Guard 47021 refers to the 21st in the series of 47-foot motor lifeboats. The call sign might be abbreviated to the final two or three numbers during operations, for example:Coast Guard zero two one.
Originally aviation mobile stations (aircraft) equipped with radiotelegraphy were assigned five-letter call signs (e.g. KHAAQ). Land stations in aviation were assigned four-letter call signs (e.g. WEAL – Eastern Air Lines, NYC.) These call signs were phased out in the 1960s whenflight radio officers (FRO) were no longer required on international flights. The Russian Federation kept FROs for the Moscow-Havana run until around 2000.
Currently, all signs inaviation are derived from several different policies, depending upon the type of flight operation and whether or not the caller is in an aircraft or at a ground facility. In most countries, unscheduledgeneral aviation flights identify themselves using the call sign corresponding to theaircraft's registration number (also calledN-number in the U.S., ortail number). In this case, the call sign is spoken using theInternational Civil Aviation Organization (ICAO)phonetic alphabet. Aircraft registration numbers internationally follow the pattern of a country prefix, followed by a unique identifier made up of letters and numbers. For example, an aircraft registered asN978CP conducting ageneral aviation flight would use the call signNovember-niner-seven-eight-Charlie-Papa. However, in the United States a pilot of an aircraft would normally omit sayingNovember, and instead use the name of the aircraft manufacturer or the specific model. At times, general aviation pilots might omit additional preceding numbers and use only the last three numbers and letters. This is especially true at uncontrolled fields (those without control towers) when reporting traffic pattern positions or at towered airports after establishing two-way communication with the tower controller. For example,Skyhawk eight-Charlie-Papa, left base. In commercial aviation, the callsign is usually the ICAOFlight number. For example,Delta Airlines Flight 744 would have the flight numberDL744 and the callsign would beDelta 744.
In most countries, the aircraft call sign or "tail number"/"tail letters" (also known as registration marks) are linked to the international radio call sign allocation table and follow a convention that aircraft radio stations (and, by extension, the aircraft itself) receive call signs consisting of five letters. For example, all Britishcivil aircraft have a five-letter registration beginning with the letter G, which can also serve for a call sign. Canadian aircraft have a call sign beginning with C–F or C–G, such as C–FABC.wing-in-ground-effect vehicles andhovercraft in Canada are eligible to receive C–Hxxx call signs, andultralight aircraft receive C-Ixxx call signs. In days gone by, even American aircraft used five-letter call signs, such as KH–ABC, but they were replaced prior to World War II by the current American system of civilian aircraft call signs (see below). One exception to the parallelism between registration and call sign is ultralight airplanes in France, who are not obliged to carry a radio and indeed often don't.
Radio call signs used for communication in crewed spaceflight are not formalized or regulated to the same degree as for aircraft. The three nations currently launching crewed space missions use different methods to identify the ground and space radio stations; the United States uses either the names given to the space vehicles, or else the project name and mission number. Russia traditionally assigns code names as call signs to individualcosmonauts, more in the manner ofaviator call signs, rather than to the spacecraft.
The only continuity in call signs for spacecraft have been the issuance of "ISS"-suffixed call signs by various countries in the amateur radio service as a citizen of their country has been assigned there. The first amateur radio call sign assigned to the International Space Station was NA1SS by the United States. OR4ISS (Belgium), DP0ISS (Germany), and RS0ISS (Russia) are examples of others, but are not all-inclusive of others also issued.
Broadcasters are allocated call signs in many countries. While broadcast radio stations will oftenbrand themselves with plain-text names, identities such as "CoolFM", "Rock 105" or "the ABC network" are not globally unique. Another station in another city or country may (and often will) have a similar brand, and the name of a broadcast station for legal purposes is normally its internationally recognized ITU call sign. Some common conventions are followed in each country.
Broadcast stations in North America generally use call signs in the international series. In the United States of America, they are used for all FCC-licensed transmitters.[2] The first letter generally isK for stations located west of theMississippi River andW for eastern stations. Historic exceptions in the east includeKYW in Philadelphia andKDKA in Pittsburgh, while western exceptions includeWJAG inNorfolk, Nebraska, andWOAI in San Antonio. All new call signs have been four-character for some decades, though there are historicalthree-character call letters still in use today, such asKSL in Salt Lake City;KOA in Denver;WHO in Des Moines;WWJ andWJR in Detroit;WJW-TV inCleveland;WBT in Charlotte;WBZ in Boston;WSM in Nashville;WGR in Buffalo;KFI;KNX andKHJ in Los Angeles; andWGN,WLS andWLS-TV in Chicago. American radio stations announce their call signs (except for rare cases in which would interfere with the broadcast of very long works of classical or opera music) at or near the top of each hour, as well as sign-on and sign-off for stations that do not broadcast 24 hours. Beginning in the early 2000s, digital subchannels were assigned a -DT# suffix, where # is the subchannel (starting with the number 2).
In Canada, the publicly ownedCanadian Broadcasting Corporation uses the prefixCB; privately owned commercial broadcast stations use primarilyCF andCH throughCK prefixes; and four stations licensed toSt. John's by theDominion of Newfoundland government retain their originalVO calls. In Mexico,AM radio stations useXE call signs (such asXEW-AM), while the majority ofFM radio and television stations useXH. Broadcast call signs are normally four or five alpha characters in length, plus the-FM,-TV, or-TDT suffix where applicable.
In South America call signs have been a traditional way of identifying radio and TV stations. Some stations still broadcast their call signs a few times a day, but this practice is becoming very rare. Argentinian broadcast call signs consist of two or three letters followed by multiple numbers, the second and third letters indicating region. In Brazil, radio and TV stations are identified by a ZY, a third letter and three numbers.ZYA andZYB are allocated to television stations;ZYI,ZYJ,ZYL, andZYK designate AM stations;ZYG is used forshortwave stations;ZYC,ZYD,ZYM, andZYU are given to FM stations.
In Australia, broadcast call signs are optional, but are allocated by theAustralian Communications and Media Authority and are unique for each broadcast station.
Most European and Asian countries do not use call signs to identify broadcast stations, but Japan, South Korea, Indonesia, the Philippines and Taiwan do have call sign systems. Spanish broadcasters used call signs consisting ofE followed by two letters and up to three digits until the late 1970s. Portugal had a similar system, their callsigns beginning withC; these also ceased to be used in the 1970s. Britain has no call signs in the American sense, but allows broadcast stations to choose their owntrade mark call sign up to six words in length.
Amateur radio call signs are in the international series and normally consist of a one or two character prefix, a digit (which may be used to denote a geographical area, class of license, or identify a licensee as a visitor or temporary resident), and a 1-, 2-, or 3-letter suffix. In Australia, call signs are structured with a two letter prefix, a digit (which identifies geographical area), and a 2, 3 or 4 letter suffix. This suffix may be followed by a further suffix, or personal identifier, such as /P (portable), /M (mobile), /AM (aeronautical mobile) or /MM (maritime mobile). The number following the prefix is normally a single number (0 to 9). Some prefixes, such as Djibouti's (J2), consist of a letter followed by a number. Hence, in the hypothetical Djibouti call sign, J29DBA, the prefix isJ2, the number is9, and the suffix isDBA. Others may start with a number followed by a letter, for example, Jamaican call signs begin with 6Y.
When operating with reciprocal agreements under the jurisdiction of a foreign government, an identifying station pre-pends the call sign with the country prefix and number of the country/territory from which the operation is occurring. For example, W4/G3ABC would denote a licensed amateur from the United Kingdom who is operating in the fourth district of the United States. There are exceptions; in the case of U.S./Canadian reciprocal operations, the country/territory identifier is, instead, appended to the call sign; e.g., W1AW/VE4, or VE3XYZ/W1.
Special call signs are issued in the amateur radio service either for special purposes, VIPs, or for temporary use to commemorate special events. Examples includeVO1S (VO1 as aDominion of Newfoundland call sign prefix,S to commemorateMarconi's first trans-Atlantic message, a single-characterMorse codeS sent fromCornwall, England to Signal Hill,St. John's in 1901) and GB90MGY (GB as a Great Britain call sign prefix,90 andMGY to commemorate the 90th anniversary of historic 1912 radiodistress calls fromMGY, theMarconi station aboard the famedWhite Star luxury linerRMSTitanic).[3]
The lateKing Hussein ofJordan was issued a special amateur license number,JY1, which would have been the shortest possible call sign issued by the Hashemite Kingdom of Jordan.
When identifying a station by voice, the call sign may be given by simply stating the letters and numbers, or using aphonetic alphabet. Some countries mandate the use of the phonetic alphabet for identification.
In wartime, monitoring an adversary's communications can be a valuable form of intelligence. Consistent call signs can aid in this monitoring, so in wartime, military units often employtactical call signs and sometimes change them at regular intervals. In peacetime, some military stations will use fixed call signs in the international series.
TheUnited States Army uses fixed station call signs which begin withW, such as WAR, used by U.S. Army Headquarters. Fixed call signs for theUnited States Air Force stations begin withA, such as AIR, used by USAF Headquarters. TheUnited States Navy,United States Marine Corps, andUnited States Coast Guard use a mixture of tactical call signs and international call signs beginning with the letterN.
In theBritish military, tactical voice communications use a system of call signs of the formletter-digit-digit. Within a standard infantry battalion, these characters represent companies, platoons and sections respectively, so that 3 Section, 1 Platoon of F Company might be F13. In addition, a suffix following the initial call sign can denote a specific individual or grouping within the designated call sign, so F13C would be the Charliefire team. Unused suffixes can be used for other call signs that do not fall into the standard call sign matrix, for example the unused 33A call sign is used to refer to thecompany sergeant major.
No call signs are issued to transmitters of the long-range navigation systems (Decca,Alpha,Omega), or transmitters on frequenciesbelow 10 kHz, because frequencies below 10 kHz are not subject to international regulations. In addition, in some countries lawful unlicensed low-power personal and broadcast radio signals (Citizen's Band(CB),Part 15 orISM bands) are permitted; an international call sign is not issued to such stations due to their unlicensed nature. Also, wireless network routers or mobile devices and computers usingWi-Fi are unlicensed and do not have call signs. On some personal radio services, such as CB, it is considered a matter of etiquette to create one's own call sign, which is called ahandle (or trail name). Somewireless networking protocols also allowSSIDs orMAC addresses to be set as identifiers, but with no guarantee that this label will remain unique. Manymobile telephony systems identifybase transceiver stations by implementingcell ID and mobile stations (e.g., phones) by requiring them to authenticate usinginternational mobile subscriber identity (IMSI).
International regulations no longer require a call sign for broadcast stations; however, they are still required for broadcasters in many countries, including the United States. Mobile phone services do not use call signs on-air because the phones and their users are not licensed, instead the cell operator is the one holding the license. However, the U.S. still assigns a call sign to each mobile-phone spectrum license.
In the United States,voluntary ships operating domestically are not required to have a call sign or license to operateVHF radios,radar or anEPIRB. Voluntary ships (mostly pleasure and recreational) are not required to have a radio. However, ships which are required to have radio equipment (most large commercial vessels) are issued a call sign.[4]
A directory of radio station call signs is called a callbook. Callbooks were originally bound books that resembled atelephone directory and contained the name and addressees of licensed radio stations in a given jurisdiction (country). Modern Electrics published the first callbook in the United States in 1909.[5]
Today, the primary purpose of a callbook is to allow amateur radio operators to send a confirmation post card, called aQSL card to an operator with whom they have communicated via radio. Callbooks have evolved to include on-line databases that are accessible via the Internet to instantly obtain the address of another amateur radio operator and their QSL Managers. The most well known and used on-line QSL databases include QRZ.COM,[6] IK3QAR,[7] HamCall,[8] F6CYV,[9] DXInfo,[10] OZ7C[11] and QSLInfo.[12]
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