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In Broadcasting and Radio communications, a call sign (also known as a '''callsign''' or '''call letters''', or abbreviated as a '''call''') is a unique designation for a transmitting station. In some countries they are used as names for broadcasting stations, but in many other countries they are not. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even Cryptographically Encoded to disguise a station's identity. INTERNATIONAL SERIES See Also: ITU prefix International call signs are formal, semi-permanent, and issued by a nation's Telecommunications Agency . They are used for Amateur , Broadcast , commercial, maritime and sometimes Military radio use (including Television in some countries). Each country has a set of alphabetic or numeric International Telecommunication Union -designated Prefixes with which their call signs must begin. For example:
The earliest allotment of call letters was made at the 1912 London International Radiotelegraphic Convention, United States Call Sign Policies which provided that the call letters of stations in the international system must each be formed of a group of three letters, which shall be distinguishable from one another. The Convention made a partial allotment of call letters among nations that signed the Convention, and the International Bureau at Berne, with the consent of such nations, modified and added to this assignment of call letters by circular of 23 April 1913. Because these assignments were originally made in the second decade of the 20th century, they often reflect a former political structure that has long since ceased to exist. For example, the ''V'' series (as in Victoria) originally was reserved for the British Empire , though Great Britain itself was assigned all of ''B'', ''G'', and ''M''; individual subseries of ''V'' were carved out and assigned to individual dominions and territories. The modern successor nations often (but not always) retain these series, in some cases supplemented by additional assignments. In 1927, the Soviet Union was assigned the entire ''U'' series; when the USSR broke up, several former Soviet republics received blocks of ''U'' call signs. (However, Russia was not a signatory to the 1912 convention, so, in 1912, ''UAA''–''UMZ'' were assigned to France and its colonies, and ''UNA''–''UZZ'' were assigned to Austria-Hungary and Bosnia-Herzegovina.) The United States was represented by the military at the 1927 conference, which is why it received (or, in some cases, retained) ''A'' (for Army) and ''N'' (for Navy). The ''W'' and ''K'' for civilian stations followed as the simple addition of a dash to the Morse Code letters ''A'' and ''N''. (However, in 1912, ''KDA–KZZ'', all of ''N'', and all of ''W'' were assigned to the United States, but all of ''A'' was assigned to Germany and its protectorates.) AVIATION Call signs in Aviation are derived from several different policies, depending on the type of flight operation being conducted, and depending on whether the caller is in an aircraft or at a ground facility. In most countries, unscheduled General Aviation flights identify themselves using the call sign corresponding to the aircraft's registration number (also called ''N-number'' in the U.S., or ''tail number''). In this case, the call sign is spoken using the 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 as ''N9876Q'' conducting a general aviation flight would use the call sign ''November niner eight seven six Quebec.'' In most countries the aircraft call sign or "tail number" or 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 5 letters. For example all British civil aircraft have five-letter call signs beginning with G. Canadian aircraft have signs beginning with C-F or C-G, such as C-FABC. Ground effect vehicles (hovercraft) in that country are eligible to receive C-Hxxx signs, and ultralight aircraft receive C-Ixxx 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 type of aircraft call sign (see below for details). The ''-'' (dash) in the registration is only written on the fuselage of the airplane for readability. In Air Traffic Management systems (ATC radar screen, flow management systems, etc.) and on flightplan forms the dash is not used (''PHVHA'', ''FABCD'', ''CFABC''). Once an aircraft has made contact with a particular air traffic control facility the call sign may be abbreviated. Sometimes the aircraft make or model is used in front of the full or abbreviated call sign, for instance, the American aircraft mentioned above might then use ''Cessna Seven Six Quebec''. Alternatively, the initial letter of the call sign can be concatenated with the final two or three characters, for instance a British aircraft registered GBFRM may identify as ''Golf Romeo Mike'' while the American aircraft might use ''November Seven Six Quebec''. The use of abbreviated call signs has its dangers, in the case when aircraft with similar call signs are in the same vicinity. Therefore abbreviated signs are used only so long as it is unambiguous. United Kingdom Civil Aviation Authority , CAP 413: ''Radiotelephony Manual'' , Edition 16, paragraph 1.8.2 and table 9. CAA, 2006. The United States does not follow the five letter call sign convention and in that country a registration number begins with the letter ''N'', followed by up to five digits and/or letters in one of these schemes: one to five numbers (''N12345''), one to four numbers and one suffix letter (''N1234Z''), or one to three numbers and two suffix letters (''N123AZ''). The numeric part of the registration never starts with zero. To avoid confusion with the digits ''1'' (one) and ''0'' (zero), the alphabetic letters ''I'' (india) and ''O'' (oscar) are not used in registration numbers. Commercial operators, including Airline s, '''air cargo''' and '''air taxi''' operators, will usually use an ICAO or FAA -registered call sign for their company, which is used together with the flight number. For example, British Airways flight 75 would use the call sign '' Speedbird Seven Five'' (with the last word properly pronounced ''fife''), since ''Speedbird'' is the registered call sign for British Airways. For these callsigns, proper usage varies by country. In some countries, such as the United States, numbers are spoken normally (for the example above, ''Speedbird Seventy-five'') instead of being spelled out digit by digit, leading to the posibility of confusion. Most other countries, such as the UK, they are spelled out. Ibid, paragraph 1.4.2(a). '''Air taxi''' operators in the United States sometimes do not have a registered call sign, in which case the prefix ''T'' is used followed by the aircraft registration number (e.g. ''Tango November Niner Eight Seven Six Quebec''). Some variations of call signs exist to express safety concerns to all operators and controllers monitoring the transmissions. Aircraft call signs will use the suffix "heavy" for large aircraft, to indicate an aircraft that is going to cause significant Wake Turbulence , e.g. ''United Two-Five Heavy''; All aircraft operating with a gross take-off weight of 255,000 lbs or more must use this suffix. These are typically Boeing 747 , 757 , 777 , or 767 , Airbus A340 , A330 and A300 , McDonnell Douglas DC-10 or MD-11 , or Lockheed L-1011 aircraft. For '''air ambulance''' or other flights involving the safety of life (such as aircraft carrying organs for transplant), the call sign prefix "Pan Pan Medical" is used before the normal call sign, e.g. ''Pan Pan Medical Three Three Alpha'' or ''Pan Pan Medical Northwest Four Five-Eight''. The word may be omitted for air ambulance services with assigned call signs, especially when they have notified air traffic control operators that they are on an air ambulance mission at the beginning of their flight and do not change from one controller to another. The Life Flight air ambulance service, for example, might simply identify as ''Life Flight Three''. |
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