The International Telecommunication Union (ITU) allocates call sign prefixes for radio and television stations of all types.
While ITU prefix rules are adhered to in the context of international broadcasting, including amateur radio, it is rarer for countries to assign broadcast call signs to conventional AM, FM, and television stations with purely domestic reach; the United States, Canada, Mexico, Japan, South Korea, the Philippines, and Argentina are among those that do.
Innovation, Science and Economic Development Canada's broadcasting rules indicate this is through a "special arrangement", without elaborating.
[2] In any case, the two countries are geographically separate enough to prevent confusion; Canada's shortwave broadcasters and amateur radio stations have always used one of its assigned ITU prefixes.
)[Note 1] Unavailable: Under present ITU guidelines the following call sign prefixes shall not be allocated.