View source for Automatic number announcement circuit

{{short description|Telecommunication facility in a telephone exchange}}
{{more citations needed|date=November 2022}}
An '''automatic number announcement circuit''' ('''ANAC''') is a component of a central office of a [[telephone company]] that provides a service to installation and service technicians to determine the [[telephone number]] of a [[local loop|telephone line]]. The facility has a telephone number that may be called to listen to an automatic announcement that includes the caller's telephone number. The ANAC facility is useful primarily during the installation of [[landline]] telephones to quickly identify one of multiple wire pairs in a bundle or at a termination point.

== Operation ==
By connecting a test telephone set, a technician calls the local telephone number of the automatic number announcement service. This call is connected to equipment at the [[telephone exchange|central office]] that uses automatic equipment to announce the telephone number of the line calling in. The main purpose of this system is to allow telephone company technicians to identify the telephone line they are connected to.

Automatic number announcement systems are based on [[automatic number identification]]. They are intended for use by phone company technicians, the ANAC system bypasses customer features, such as [[unlisted number]]s, [[caller ID]] blocking, and outgoing [[call blocking]]. 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".

Most ANAC systems are provider-specific in each wire center, while others are regional or state-/province- or [[telephone numbering plan|area-code]]-wide. No official lists of ANAC numbers are published, as telephone companies guard against abuse that would interfere with availability for installers.<ref>{{cite web |date=Jan 4, 2011 |title=Bell Canada → [Internet] What is the number to dial to get the phone line #? |url=http://www.dslreports.com/forum/r25283784-Internet-What-is-the-number-to-dial-to-get-the-phone-line- |website=DSLReports Forums}}</ref>

==Exchange prefixes for testing==
The [[North American Numbering Plan]] reserves the exchange (''central office'') prefixes ''958'' and ''959'' for [[plant test number|plant testing]] purposes.<ref name="telcordia2000">{{cite book
|title=Telcordia Notes on the Network
|publisher=Telcordia Technologies
|work=Special Report SR-2275, Issue 4
|date=October 2000
|page=8-8
}}</ref> Code 959 with three or four additional digits is dedicated for access to office test lines in [[local exchange carrier]] and interoffice carrier central offices. The specifications define several test features for line conditions, such as quiet line and busy line, and test tones transmitted to callers. Telephone numbers are assigned for [[ringback number|ring back]] to test the ringer when installing [[telephone]] sets, [[milliwatt test|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).

ANAC services are typically installed in the ''958'' range, which is intended for communications between central offices.<ref name="telcordia2000"/> In some area codes, multiple additional prefixes may be reserved for test purposes. Many area codes reserved 999; 320 was also formerly reserved in [[Bell Canada]] territory.

Other carrier-specific North American test numbers include [[555 (telephone number)|555-XXXX]] numbers (such as 555–0311 on [[Rogers Communications]] in Canada) or [[vertical service code]]s, such as *99 on Cablevision/Optimum Voice in the United States. [[MCI Inc.]] (United States) provides [[Automatic number identification|ANI]] information by dialing 800-444-4444.

==Telephone numbers==
Plant testing telephone numbers are carrier-specific, there is no comprehensive list of telephone numbers for ANAC services. In some communities, test numbers change relatively often.{{dubious|date=November 2022}}  In others, a major incumbent carrier might assign a single number which provides test functions on its network across an entire numbering plan area, throughout an entire province or state, or system-wide.{{citation needed|date=November 2022}}

Some telecommunication carriers maintain [[toll-free number]]s for ANAC facilities. Some national toll-free numbers provide [[automatic number identification]] by speaking the telephone number of the caller, but these are not intended for use in identifying the customer's own phone number. They are used for the agent in a [[call center]] to confirm the telephone a customer is calling from, so that the customer's account information can be displayed as a "[[screen pop]]" for the next available [[customer service]] representative.

==See also==
* [[Plant test number]]
* [[Ringback number]]

==References==
{{Reflist|30em}}

{{DEFAULTSORT:Automatic Number Announcement Circuit}}
[[Category:Telephone numbers]]
[[Category:Telephony signals]]