Call sign

A callsign is a "code name" for a radio station that is a unique identifier. Callsigns may be:

Formal, issued by a nation's telecommunication agency for long periods of time
Informal, such as used by police units or businesses,
Tactical, used for police and changed frequently for security reasons

Formal callsigns for each country have their own code prefixes, based on the ITU codes. For example:

The U.S.A. uses the prefixes: W, K, N, and AAA to ALZ
France uses the prefixes: F, TM
Chad uses the prefix: TT
Italy uses the prefix: I

Amateur Callsigns

Amateur callsigns normally have a prefix, a zone number and a postfix (suffix). The number following the prefix is normally one figure (0 to 9). Some prefixes, such as, Djibouti (J2), have two numbers, since the first one identifies the country.

The postfix identifies the individual amateur station. It may be of 1 character to 3 character.

For example is: IK1TZO where I it's the prefix for Italy (K is a letter used in conjunction with I, since the Radio Amateurs are too much to be handled with only one character), 1 is the zone in Italy correspondent to the Piemonte region, TZO are three characters that identify me.

Another example is WB3EBO. W indicates the callsign is from the United States B indicates the holder has a General or Technician-class license 3 is for stations in Maryland, Pennsylvania, or the District of Columbia. EBO is the unique station identifier.

Broadcast Callsigns

Stations in the U.S. and Canada have three- or four-letter assigned callsigns. Many of these, such as those for Baltimore television station WJZ, have long historical associations. Others are changed frequently as the station changes format. Many stations prefer not to use callsigns at all, since a slogan is more easily remembered by listeners filling in diaries for the Arbitron Company's radio ratings.

In the United States, the vast majority of stations east of the Mississippi River have callsigns beginning with "W". Stations west of the Mississippi River use "K". One prominent exception is KDKA, in Pittsburgh, the first broadcasting station in the world.

In Canada, stations of the Canadian Broadcasting Company tend to identify themselves as "CBC Radio One/Two" of a city. Commercial stations use a four-letter callsign.

Tactical Callsigns

Police units in the United States tend to use a callsign consiting of a letter of the police phonetic alphabet followed by one or two numbers. For example, "Mary One" would identify the head of the city's Homicide Division.

The United States Army uses a callsign series of letter-number-letter-postfix that changes every day.

The United States Air Force uses semi-fixed callsigns consisting of a name followed by a two or three digit number. The name is assigned to a unit on a semi-permanent basis. 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.