In broadcasting and radio communications, a
call sign (also known as a callsign, call-
name or call letters, or abbreviated as a
call) is a unique designation for a transmit-
ting 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 en-
coded to disguise a station’s identity.
The use of callsigns as unique identifiers
dates to the landline railroad telegraph sys-
tem. Because there was only one telegraph
line linking all railroad stations, there needed
to be a way to address each one when send-
ing a telegram. In order to save time, two let-
ter identifiers were adopted for this purpose.
This pattern continued in radiotelegraph op-
eration; radio companies initially assigned
two-letter identifiers to coastal stations and
stations aboard ships at sea. These were not
globally unique, so a one-letter company
identifier (for instance, ’M’ and two letters as
a Marconi Station) was later added. By 1912,
the need to quickly identify stations operated
by multiple companies in multiple nations re-
quired an international standard; an ITU pre-
fix would be used to identify a country, and
the rest of the callsign an individual station
in that country.
International call signs are formal, semi-per-
manent, and issued by a nation’s telecommu-
nications agency. They are used for amateur,
broadcast, commercial, maritime and some-
times military radio use (including television
in some countries).
Each country has a set of alphabetic or nu-
Union-designated prefixes with which their
call signs must begin. For example:
• Australia uses AX, VH–VN and VZ.
• Canada uses CF-CK, CY-CZ, VA-VG, VO
(Newfoundland), VX-VY, and (rarely)
• China uses BAA-BZZ, XSA-XSZ, 3HA-3UZ,
VR (Hong Kong), XX (Macao).
• Germany uses DA-DR
• Korea uses KR, KOR, ROK
• Japan uses JA–