Call sign

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

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:
* Australia uses AX, VHâ€"VN, and VZ.
* Canada uses CF-CK, CY-CZ, VA-VG, VO, VX-VY, and XJ-XO.
* Brazil uses PPâ€"PY and ZVâ€"ZZ.
* Chad uses TT.
* Honduras uses HQâ€"HR.
* India uses ATâ€"AW, VTâ€"VW, and 8Tâ€"8Y.
* Japan uses JAâ€"JS, 7Jâ€"7N, and 8Jâ€"8N.
* Russia uses R and UAâ€"UI.
* The United Kingdom uses G, M, VS, ZBâ€"ZJ, ZNâ€"ZO, ZQ, and 2.
* The United States uses K, W, N, and AAâ€"AL.

Because these assignments were originally made in the early part of the twentieth century, they often reflect a former political structure that has long since ceased to exist. For example, the V series was originally reserved for the British Empire; individual subseries were carved out and assigned to individual dominions and territories. The modern successor nations retain these series, in some cases supplemented by additional assignments. Similarly, the Soviet Union had the entire U series; when the USSR broke up, several former Soviet republics received blocks of U call signs.

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 correseponding 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 (N in the U.S.), followed by a unique identifier made up of letters and numbers. For example, an aircraft registred 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)

Once an aircraft has made contact with a particular air traffic control facility the call sign may be abbreviated. For example a Canadian aircraft initially identified as C-GRTY might then identify as romeo tango yankee but the omission must be initiated by the air traffic services agency, not the pilot. The American aircraft mentioned above might then use seven six quebec. Sometimes the aircraft make or model is used in front of the full or abbreviated call sign. 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.

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 airlines, 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 seventy five, since Speedbird is the registered call sign for British Airways. When these call signs are used, numbers are pronounced normally, instead of being spelled out digit by digit, further reducing confusion. 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" to indicate a large aircraft, e.g'. United twenty-five Heavy.; these are typically Boeing 747 or 767, Airbus A340, 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 callsign prefix Lifeguard is used before the normal callsign, e.g. Lifeguard three three alfa or Lifeguard Northwest four fifty-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.

Glider pilots often use a supplementary number (the competition number) in their call signs.

Military flights use a variety of registered call signs with flight numbers, just like commercial operators. e.g. Navy Golf Alfa Kilo 21, REACH 31792.

Ground facilities identify themselves by the name and function of the facility: e.g. Seattle Tower for the tower controller's position, or Boston Center for an Area Control Center.

Ships and boats

Merchant vessels are assigned a call sign by their national licensing authority. In the case of states such as Liberia or Panama, which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters (for example, 3LXYZ). United States civilian vessels are given call signs beginning with the letter W. Originally both ships and broadcast stations were given call signs in this series consiting of three or four letters, but gradually American-flagged vessels were given callsigns with mixed letters and numbers.

Leisure craft with VHF radios may not be assigned callsigns, in which case the name of the vessel is used instead.

Amateur radio

Amateur radio call signs are in the international series and normally consist of a one- or two-character prefix, a number (which sometimes corresponds to a geographic area within the country), and a 1, 2, or 3 character suffix. 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 is J2, the number is 9, and the suffix is DBA. Others may start with a number followed by a letter, for example, Jamaican call signs begin with 6Y.

The numbers are sometimes assigned geographically. In the Italian call sign, IK1TZO, IK is the prefix, the number component is 1 and corresponds to the Piedmont, Aosta Valley and Liguria regions, and TZO is the suffix. Another example is WB3EBO. WB is the prefix, the number 3 most often indicates that the station is located in Delaware, Maryland, Pennsylvania, or the District of Columbia, and the suffix is EBO. For district numbers within the United States, see ARRL map.

Broadcast call signs

North America

Broadcast stations in North America generally use call letters in the international series. There are some common conventions followed in each country. In Canada, call signs begin with the letter C, except for four stations in St. John's which begin with VO. Mexican call signs begin with an XE for medium-wave (AM) radio stations and XH in other cases. In the United States, the first letter generally is K for stations west of the Mississippi River and W for those east of the Mississippi. There are a number of exceptions, such as KYW in Philadelphia and WFAA in Dallas, but these are historical artifacts from a rule change in the 1930s, and most of these exceptions are located in the states immediately to either side of the river. The westernmost station in the continental United States beginning with W is WOAI in San Antonio. WVUV in Pago Pago, American Samoa, is the westernmost station with a W call-sign.

Government-operated international broadcasters, such as Radio Canada International and Voice of America, are not assigned call signs; however, privately-operated shortwave stations, like WWCR and CFRX, are.

Australia

In Australia, broadcast call signs begin with a single-digit number indicating the state or territory, followed by two letters for AM stations and three for FM. Some AM stations retain their old call signs when moving to FM, or just add an extra letter to the end. Australian broadcast stations originally used the prefix VL-, but since Australia has no nearby neighbors, this practice was soon discarded, although the VL prefix can still be implied in an international context. (Certain ABC radio stations, particularly outside of metropolitan areas, may use five-letter call signs for FM stations: xABCFM for ABC Classic FM, xABCRN for Radio National, and xABCRR for ABC Local Radio - the x being the state number.)

Television station call signs begin with two letters usually denoting the station itself, followed by a third letter denoting the state. For example, NBN's call sign stands for Newcastle Broadcasting, New South Wales. There are some exceptions:
*ABC television stations outside of state capitals add a fourth letter (and in rare cases a fifth) between AB and the state. This is used to denote the area, e.g. the Newcastle station is known as ABHN, standing for Australian Broadcasting Corporation, Hunter Valley, New South Wales. State capital stations follow the same rule as commercial stations, also using AB as the first two letters; for example, ABN is Sydney's ABC television station.
*SBS television stations all use SBS in their call signs, regardless of the state. Also, SBS FM radio stations use a five-letter call sign, xSBSFM. (Sydney and Melbourne's AM stations use xEA, short for Ethnic Australia.)
*Commercial station Imparja Television uses IMP, even though they are based in Alice Springs in the Northern Territory.
*Community television station Television Sydney uses TVS as its call sign, although being a New South Wales-based station it should have a call sign ending in "N".

Letters and numbers used by Australian stations:
*Radio
**1 - Australian Capital Territory (new designation)
**2 - New South Wales, the Australian Capital Territory and some external territories
**3 - Victoria
**4 - Queensland
**5 - South Australia
**6 - Western Australia
**7 - Tasmania
**8 - Northern Territory
*Television
**N - New South Wales
**Q - Queensland
**V - Victoria
**S - South Australia
**C - Canberra and the Australian Capital Territory
**W - Western Australia
**D - Darwin and the Northern Territory
**T - Tasmania

New Zealand

The use of broadcast callsigns in New Zealand historically consisted of a digit, and two letters for AM or three for FM. The usage was:
*Number
**1 - Northern half of the North Island
**2 - Southern half of the North Island and the Nelson region
**3 - South Island, north of the Waitaki River, excluding Nelson
**4 - South Island, south of the Waitaki River
*First letter
**X - private commercial station
**Y - Radio NZ, non-commercial (National Programme, Concert Programme) and Access Radio Wellington (2YB)
**Z - Radio NZ, commercial (now mostly The Radio Network)

For example - 1ZB was a Radio NZ commercial station in Auckland; 4XF was Foveaux Radio in Invercargill (now More FM); 4YC was the Concert Programme in Dunedin.

FM stations appeared to have no standard format for the letters, just picking three that 'fit' the station. To make matters more confusing, some stations such as 4ZA-FM (now Classic Hits Southland 98.8FM) and 4XO Gold (now More FM Dunedin) retained their AM callsigns.

Auckland, Wellington, Christchurch and Dunedin as major centres for the four regions had specific Radio NZ callsigns used:
* xYA - National Programme
* xYC - Concert Programme
* xZB - Community Network commercial
* xZM - Music commercial (except Dunedin)

During the early 1990's the use of callsigns became less common, to the point that most broadcasters do not use them at all. Some are retained in some form for branding - for example, 4XO Dunedin (until it was rebranded More FM Dunedin in 2004), Newstalk ZB (using the old 1ZB, 2ZB, 3ZB, 4ZB and various other Radio NZ commercial frequencies) and ZM (originally ZMFM, replacing the old 1ZM, 2ZM and 3ZM, now nationwide). Stations licensed since 1990 have not had callsigns allocated.

Europe/Asia

In Europe and much of Asia, call signs are normally not used for broadcast stations. Japan, South Korea, the Philippines and Taiwan are exceptions to this general rule. Other countries have yet other formats for assigning call signs to domestic services.

Military call signs

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 employ tactical call signs and sometimes change them at regular intervals. In peacetime, some military stations will use fixed call signs in the international series.

U.S. Army

The United States Army uses fixed call signs which begin with W, such as WAR, used by U.S. Army Headquarters.

U.S. Air Force

Fixed call signs for the United States Air Force stations begin with A, such as AIR, used by USAF Headquarters.The USAF also uses semi-fixed identifiers consisting of a name followed by a two or three digit number. The name is assigned to a unit on a semi-permanent basis; they change only when the U.S. Department of Defense goes to DEFCON 3. For example, JAMBO 51 would be assigned to a particular B-52 aircrew of the 5th Bomb Wing, while NODAK 1 would be an F-16 fighter with the North Dakota Air National Guard. The most recognizable call sign of this type is Air Force One, used when any Air Force aircraft is transporting the U.S. President. Individual military pilots or other flight officers usually adopt a personal aviator call sign.

U.S. Navy/Coast Guard

The United States Navy and United States Coast Guard use a mixture of tactical call signs and international call signs beginning with the letter N. For example, the carrier USS John F. Kennedy has the call sign NJFK.

British Army

Tactical voice communications ("combat net radio") use a system of callsigns of the form letter-digit-digit. Within a standard infantry battalion these characters represent companies, platoons and sections respectively, so that 3 Section, 1 Platoon of B Company might be F13. In addition, F13A might be the 2ic of that section, in charge of its Delta fire team.

Note that the letter part of the callsign is not the company's own letter (B vs F in the above example) - indeed, the letter designations are randomly assigned using BATCO sheets and change along with the BATCO codes every 24 hours. This, together with frequency changes and voice procedure aimed at making every unit sound the same, introduces a degree of protection against simple traffic analysis and eavesdropping.

Not all radio users fit into the standard battalion model, but in order to continue the obfuscation they will be assigned a callsign that appears to be part of such a system. Presumably, the well-known B20 falls into this category.

Finally, the controller of each net has the callsign 0 ("zero"). There may also be a second controller - either a backup station or a commander who has delegated communication tasks to a signaller but may occasionally wish to speak in person - with the callsign 0A ("zero alpha").

Transmitters requiring no call signs

No call signs are issued to transmitters of long-range navigation systems (LORAN-C, Decca, Alpha, Omega) or transmitters on frequencies below 10 kHz, because frequencies below 10 kHz are not subject to international regulations. In addition, in some countries low-power personal and broadcast radio (Citizen's Band, Part 15, and the like) is allowed; a call sign is not always required for such stations, though especially on personal radio services it is considered a matter of etiquette to create one's own.

References

*United States Federal Aviation Administration, Aeronautical Information Manual, Official Guide to Basic Flight Information and ATC Procedures, 2004. Chapter 4, Section 2

External links

*United States Call Sign Policies
*United States "FCC" callsign search
*Amateur Call Prefixes
*Ham Radio call signs

Call sign: Encyclopedia BETA

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