Area code 644

Area code 600 is a rarely used non-geographic Canadian area code, reserved for specialized telecommunication uses such as Teletype, caller-pays cellular, ISDN and mobile satellite communication services. One of the code's most common uses is to provide satellite phone service in remote areas of Northern Canada where conventional telecommunications infrastructure is not available.

Exchanges in the 600 code are assigned according to a special set of guidelines issued by the Canadian Radio-television and Telecommunications Commission. The guideline does not define which services qualify for the non-geographic numbers, but specifies that:

In the context of NPA 600, Non-Geographic Services are specific telecommunications services that are: 1) approved by the CRTC, or confirmed by the CRTC as not requiring approval, 2) provided by Canadian Telecommunications Service Providers (TSPs), 3) made available on a non-geographic basis to customers located in Canada, and 4) accessible from at least one public Canadian telecommunications network other than the Code Holder's network.

These uses (initially, TWX teleprinter data) were designated with the area code 610 in 1962 and reassigned to 600 in 1992 so that 610 could be assigned to Pennsylvania as an ordinary geographic area code.

There are 798 possible +1-600- exchange prefixes (200 to 999, with 555 and 911 not issued). Six relief area codes (622, 633, 644, 655, 677 and 688) are reserved by NANPA as subject to assignment in Canada for expansion of non-geographic services but have never been used. There is no area code 666. Each block of 10000 numbers is assigned to one carrier only; there is no number portability or number pooling in +1-600. A carrier offering multiple, different non-geographic services may request separate exchange prefixes for each.

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