An '''automatic number announcement circuit (ANAC)''' is a special [[telephone number]] that is meant to be used by [[Telephone company|phone company]] technicians and other telecommunications technicians to determine the phone number of a particular line.

The way an ANAC works is fairly simple: A technician will call a local ANAC's phone number. This number connects to a computer at a local [[Telephone exchange|central office]] which uses a voice synthesizer or digital samples to "speak" the phone number of the line calling in. The main purpose of this system is to allow phone company technicians to identify which telephone line they are connected to. Because this system is based on [[automatic number identification]] (not caller ID) and meant for phone company technicians, the ANAC system works with unlisted and even numbers with [[caller ID]] blocking.

Some ANACs are very regional or local in scope, while others are state or [[Telephone numbering plan|area code]]-wide. There appears to be no national cohesive system for them. Every telephone company (big or small) can determine its own ANAC for each individual central office, leading to a mish-mash of overlapping and/or spotty coverage.

In most North American area codes, 958-xxxx and 959-xxxx exchanges are reserved for various local and long-distance test purposes (a few may also reserve 999-xxxx); ANAC numbers sometimes appear in the 958-xxxx range but there is no requirement that they reside there. Other local test numbers may include [[Ringback number|ringback]] (to test the ringer when installing telephones) and [[Loop around|loop line]]s (which connect a call to another inbound call to the same or another test number). Some carriers (such as [[Bell Canada]]) have been known to program [[payphone]]s to disable calls to 958 or 959 test lines.

Some large telephone companies have toll-free numbers set up, but these numbers remain undisclosed to prevent abuse.

There are some private national toll-free numbers that use [[Automatic number identification|ANI]] and then have a computer read back the number that is calling, but these are not intended for use in identifying your phone number, they are used in order for you to confirm the phone you are calling from so that a computer can automatically pull up your account for the next available customer service representative. However, if one were to call up one of these numbers, listen for the number confirmation and hang up, they would in effect be using this system as if it were an ANAC.

[[Category:Telephony]]