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Call signs are frequently still used byNorth Americanbroadcast stations, in addition toamateur radio and other international radio stations that continue to identify bycall signs worldwide. Each country has a different set of patterns for its own call signs. Call signs are allocated toham radio stations inBarbados,Canada,Mexico and theUnited States.
Many countries have specific conventions for classifying call signs by transmitter characteristics and location. The call sign format forradio andtelevision call signs follows a number of conventions. All call signs begin with a prefix assigned by theInternational Telecommunication Union (ITU). For example, theUnited States has been assigned the following prefixes:AAA–ALZ,K,N,W. For a complete list, seeinternational call sign allocations.
Pertaining to their status as former or current colonies, all of theBritish West Indies islands shared theVS,ZB–ZJ, andZN–ZO prefixes. The current, largely post-independence, allocation list is as follows:
Cuba uses the prefixesCL–CM,CO, andT4, with district numbers from 0 to 9 for amateur operations.
The Dominican Republic uses the prefixesHI–HJ.
All of the French possessions share the prefixF. Further divisions that are used by amateur stations are:
Haiti has been assigned the call sign prefixesHH and4V.
TheKingdom of the Netherlands use thePA–PI prefixes, while theNetherlands Antilles use thePJ prefix.Aruba has been assignedP4 by theITU.
The island nation ofTrinidad and Tobago use the9Y–9Z prefixes.
Canadian broadcast stations are assigned a three-, four-, or five-letter base call sign (not including the "-FM", "-TV" or "-DT" suffix) beginning withCB,CF,CH,CI,CJ,CK,VF, orVO. The "CB" series calls are assigned toChile by the ITU, but Canada makesde facto use of this series anyway for stations belonging to, but not exclusively broadcasting programs from, theCanadian Broadcasting Corporation (CBC).[2]
Several other prefixes, includingCG,CY-CZ,VA-VE,VG, and theXJ-XO range, are available, but are not used in broadcasting. Conventional radio and television stations almost exclusively use "C" call signs; with the exception of a few commercial radio stations inSt. John's, Newfoundland and Labrador which existed prior to the admission of Newfoundland as a province in 1949, the "V" calls are restricted to specialized uses such asamateur radio.
Mexican broadcast stations are assigned call signs beginning with "XE" (formediumwave andshortwave stations) or "XH" (forFM radio andtelevision stations), followed by one and up to five letters and a suffix according to the band in which they broadcast, these suffixes are: "-AM", "-OC" (shortwave orOnda Corta), "-FM" and "-TDT" (Terrestrial Digital Television). The "-OL" (longwave orOnda Larga) and "-TV" suffixes are currently phased out as those bands are no longer used. Some FM and television stations have call signs beginning with "XE", usually reserved for AM radio stations. Most of these "XE" cases in FM and television stations were solicited by the concessionaires themselves so the stations would have the same call sign as an existing AM station (as it is the case ofXEW-AM,XEW-TV andXEW-FM, all founded and owned by theAzcárraga family), while others are for disambiguation (likeXHTV-TV andXETV-TV orXEIMT-TV andXHIMT-TV). All TV stations originally assigned with the "-TV" suffix, had been given the "-TDT" suffix as they made thedigital switchover.
Television stations are required to identify every 30 minutes; there has been no equivalent requirement in radio since 2014. Televisionrebroadcasters are assigned the call signs of the station they are licensed to retransmit; for instance,XEZ-TDT, located on Cerro El Zamorano inQuerétaro, has a repeater on Cerro Culiacán servingCelaya,Guanajuato, which is also XEZ-TV.Digital subchannels are not assigned a distinctive call sign; they keep the call sign of the station. The technical guidelines for digital television stations stipulate the use ofPSIP short names matching the parent station (e.g.XHTDMX2, XHTDMX3).
Amateur radio stations in Mexico use "XE1" for the central region, "XE2" for the northern region, and "XE3" for the southern region. "XF" prefixes indicate islands. "XF4" is usually used for theRevillagigedo Islands and nearby islets. Special call signs for contests or celebrations are occasionally issued, often in the 4A and 6D series, although these will follow the usual district numbering system (4A3 for the south, etc.).
The earliest identification, used in the 1910s and into the early 1920s, was arbitrary. The U.S. government began requiring stations to use three-letter call signs around 1912, but they could be chosen at random. This system was replaced by the basic form of the current system in the early 1920s. Examples of pre-1920 stations include 8XK inPittsburgh,Pennsylvania, which becameKDKA in November 1920, andCharles Herrold's series of identifiers from 1909 inSan Jose, California: first "This is the Herrold Station" or "San Jose calling",[3] then the call signs FN, SJN, 6XF, and 6XE, then, with the advent of modern call signs, KQW in December 1921, and eventuallyKCBS from 1949 onward.
All broadcast call signs in the United States begin with eitherK orW, with "K" usually west of theMississippi River and "W" usually east of it. Initial lettersAA throughAL, as well asN, are internationally allocated to the United States but are not used for broadcast stations.
In the United States, broadcast stations have call signs of three to seven characters in length, including suffixes for certain types of service, but the minimum length for new stations is four characters, and seven-character call signs result only from rare combinations of suffixes.
The rules governing call signs for stations in the United States are set out in the FCC rules, 47C.F.R. chapter I. Specific rules for each particular service are set out in the part of the rules dealing with that service. A general overview of call sign formats is found at47 CFR2.302. Rules for broadcast stations' call sign are principally defined in47 CFR73.3550.