Call sign

Call sign is a unique designation for a transmitter station. In broadcasting and radio communications, a call sign (also known as a call name or call letters—and historically as a call signal—or abbreviated as a call) is a unique designation for a transmitter station. In the United States of America, they are used for all Federal Communications Commission licensing, from commercial broadcasting down to amateur operators. 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.

History

The use of call signs as unique identifiers dates back to the landline railroad telegraph system. Because there was only one telegraph line linking all railroad stations, there needed to be a way to address each one when sending a telegram. In order to save time, operators would send the message to all stations and the one that it was addressed to would respond. To save time, operators began to shorten the addresses. In addition to wanting to save time, it was also important to reduce transmission time because the telegraph lines were leased.

Usage

Call signs are used on a wide variety of radio communications. They are used by commercial broadcasting stations, amateur radio, citizens band radio, and even some police, fire and emergency medical communication services. In broadcasting, call signs are located at the beginning of a broadcast or transmission to identify the station or broadcaster.

International call signs

International call signs are used also in two-way radio communications, such as amateur radio. They are assigned by the International Telecommunication Union (ITU) to its member countries and each country is assigned a set of alphabetic call sign prefixes.

See also

• Amateur radio call signs
• Aviation call signs
• Maritime mobile service identity
• Military call sign
• Pseudonym
• Radio alphabet
• Signalling control