Call signs in Australia

Call signs in Australia are allocated by the Australian Communications and Media Authority and are unique for each broadcast station. The use of callsigns on-air in both radio and television in Australia is optional, so many stations used other on-air identifications. Australian broadcast stations officially have the prefix VL- and originally all callsigns used that format, but since Australia has no nearby neighbours, this prefix is no longer used except in an international context.
Call sign blocks for telecommunication.
The International Telecommunication Union has assigned Australia the following call sign blocks for all radio communication, broadcasting or transmission:
While not directly related to call signs, the International Telecommunication Union (ITU) further has divided all countries assigned amateur radio prefixes into three regions; Australia is located in ITU Region 3. It is assigned ITU Zones 55, 58 and 59, with the Pacific Islands in Australian jurisdiction in Zone 60.
Australia is assigned CQ Zones 29 & 30.
Call signs for radio.
All radio call signs begin with a single-digit number indicating the state or territory, followed by two or three letters. In most cases, two letters are used for AM stations and three for FM, but there are some exceptions, such as 5UV in Adelaide, which broadcasts on an FM frequency, and 3RPH in Melbourne, which broadcasts on an AM frequency. While some AM stations retained their old call signs when moving to FM, most add an extra letter to the call sign. For instance, when 7HO Hobart became an FM station, it adopted the callsign 7HHO.
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. Also, SBS FM radio stations use a five-letter call sign, "xSBSFM". (Sydney and Melbourne's AM stations use "2EA" and "3EA", meaning "Ethnic Australia".)
There are a number of exceptions:
The following are lists of Australian radio station call signs.
Australian radios usually had the positions of radio stations marked on their dials.
Australia's postcodes, introduced in 1967, use the same digit as the radio callsigns, followed by an additional three digits (eg. NSW: 2XXX, Victoria: 3XXX, etc.).
There is an urban myth that call signs were based on Australian military districts but this incorrect as the following list of military districts show: 1 = Queensland; 2 = New South Wales; 3 = Victoria; 4 = South Australia; 5 = Western Australia; 6 = Tasmania; 7 = Northern Territory; 8 = New Guinea, and Papua.
Television call signs.
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:
Amateur radio.
Amateur radio in Australia has its own set of call signs, managed by the Australian Maritime College, normally starting with the prefix VK, the state identifier, and then 1,2,3, or 4 letters. 
As of July 29th 2020 - the following AR callsign structure is in place in Australia: 
Advanced VK$aa, VJ$a, VK$a, VL$a
Advanced/Standard/Foundation VK$aaa-VK$zzz
Repeater / Beacon VK$Raa-VK$Rzz
It is also no longer necessary to change one's callsign should the amateur move states within Australia or advance to a higher licence class.
Amateur radio or ham radio call signs are unique identifiers for the 19,500 licensed operators in Australia. Call signs are regulated internationally by the ITU as well as nationally by the Australian Communications and Media Authority (ACMA) which is Australia's regulator for broadcasting, administering spectrum use through the provisions of the Radio-communications Act 1992. ACMA is also responsible for amateur radio licensing. The Wireless Institute of Australia had the responsibility for the management of amateur station call signs from 2 March 2009 until February 2019 .
Amateur radio call sign assignments within Australia.
The usual prefix for Australian amateur call signs is VK. The numeral that separates the prefix from the suffix indicates the state/territory in which the operator is licensed.
Since 1 November 2009 callsigns in the VK9 region have been treated the same as all other call areas, and individual islands are no longer designated by a special letter.
Operator class call signs.
With the exception of repeaters and beacons, the ACMA removed the relationship between the first letter of a call and the type of licence as of July 29, 2020. Should someone move state they no longer need to change their call for one with their new states number in, they can retain their existing callsign. 
Prior to this change, the following structure was in place: 
AX prefix.
A special event prefix of 'AX' can be substituted for 'VK' on occasions of national significance (e.g. Sydney Olympic Games) and each year on Australia Day, Anzac day and World Information Society Day.
VI prefix.
A special event prefix of 'VI' can be substituted for 'VK' on occasions of state/territory significance.
VJ & VL prefixes.
The special (contest only) prefixes of 'VJ' & 'VL' are only used with 2x1 contest call signs, implemented from July 29th 2020. 2x1 call signs may ONLY be used during contests.
Overseas visiting amateurs.
Visiting amateurs who qualify under a two-party joint agreement between Australia and their home country can use their home call sign, and attach a '/VK' after it. If a visiting amateur is issued an Australian call sign, they can combine both (e.g. VK1AAA/WA7AAA).
Visiting amateurs holding a "full" callsign from a CEPT agreement (TR61/01) signing country PREFIX their home callsign with VKn/ (where n is the number for the state or territory they are in) and may operate for up to 3 months within Australia after which time application for a reciprocal licence under CEPT agreement TR61/02 is required.
Call sign history.
David Burger has written the definitive history of call sign allocation in the country.
Wireless experimenters were in most states by 1897, and the first list of call signs and licensees is from 1911. In 1912 the first system of a designated range for each state was issued by the PMG Department based on an XAA–XZZ block of letters. When all the three letter call signs were issued, provision was made to expand to four (e.g. XAAA). In 1914 a numeral was inserted after the 'X' to indicate the state (e.g. XAA became X1AA).
In 1927 the Washington Radiotelegraph Conference decreed that Australia should use the prefix range of VHA–VNZ for communication identification. However, amateur radio itself was not subject to this designation, and 'OA' became effective for amateurs from 1 February 1927. "O" was for Oceania and "A" for Australia. By 1929 Australia began the practice of using 'VK' for amateurs as well.
With a lack of official issuance, though, some radio experimenters continued with various formats such as XA-4CD, OA2-BH, VK.2AK and VK-4SU. There was even VK3D.L. and VK3H-W.
1947 Atlantic City convention and subsequent.
As of 19 September 1947 Australia adopted the ITU international call sign protocol and recognised amateur radio stations as valid licensees. The ITU issued Australia with the AXA–AXZ, VHA–VNZ and VZA–VZZ blocks.
VK#xx and VK#Axx call signs were issued to amateurs.
Changes within Australia happened according to this table:
State indicators.
Letters and numbers used by Australian stations: