Some carriers have been known to disable payphone calls to 958 or 959 test lines, such as Bell Canada's system-wide ANAC line at (area code) 958-2580. As widespread inefficiencies in numbering (such as the assignment of entire blocks of 10000 numbers to every competing carrier in every small village to support local number portability schemes) have created shortages of available numbers, these prefixes are often "reclaimed" and issued as standard exchanges, moving the handful of numbers in them to one standard test exchange (usually 958). Many area codes reserved 999 320 was also formerly reserved in Bell Canada territory. In some area codes, multiple additional prefixes had been reserved for test purposes, in addition to the standard 958 and 959. ANAC numbers can also appear in the 958 range, but there is no requirement that they reside there. (One exception is Winnipeg, which reserves 959 only.) Numbers within this block are used for various test utilities such as a ringback number (to test the ringer when installing telephone sets), milliwatt tone (a number simply answers with a continuous test tone) and a loop around (which connects a call to another inbound call to the same or another test number). Under the North American Numbering Plan, almost all North American area codes reserve telephone numbers beginning with 958 and 959 for internal local and long-distance testing (respectively), sometimes called plant testing. No official lists of ANAC numbers are published as telephone companies believe overuse of these numbers could make them more likely to be busy when needed by installers.
Every telephone company, whether large or small, determines its own ANAC for each individual central office, which tends to perpetuate the current situation of a mess of overlapping and/or spotty areas of coverage. Some ANACs are very regional or local in scope, while others are state-/province- or area-code-wide: there appears to be no consistent national system for them. Installers of multi-line business services where outgoing calls from all lines display the company's main number on call display can use ANAC to identify a specific line in the system, even if CID displays every line as "line one". The main purpose of this system is to allow telephone company technicians to identify the telephone line they are connected to.Īutomatic number announcement systems are based on automatic number identification, and meant for phone company technicians, the ANAC system works with unlisted numbers, numbers with caller ID blocking, and numbers with no outgoing calls allowed. This call is connected to equipment at a local central office that uses a voice synthesizer or digital samples to announce the telephone number of the line calling in. A technician calls the local telephone number of the automatic number announcement service.
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