Automatic number identification

Automatic number identification is a feature of Inward WATS Service (Wide Area Telephone Service) which permits subscribers to display or capture the telephone numbers of calling parties. ANI service was created by AT&T for internal long-distance billing purposes, and is not related to newer Caller ID services. Inward WATS Service is purchased by customers so that other telephone users (for example, prospective customers) can call the number toll free. The customer is issued a distinctive telephone number beginning with a special area code such as 800, or more recently, 888, 877, or 866. Subscribers to these numbers are typically called Inward WATS subscribers.

A related piece of information conveyed to the Inward WATS service subscriber is the DNIS or Dialed Number Identification Service. This is the number that the caller dialed when accessing the "800" service. With the information, the service provider can have several "800," or "toll-free," numbers directed to the same call center and provide unique service based on the number dialed.

ANI actually has two components, the Information Digits and the calling party telephone number. The "information digits" identify the class of service. According to the current "ANI II" specification (http://www.atis.org/inc/docs/finaldocs/98011620.doc), the codes are as follows:

00 - Plain Old Telephone Service (POTS), a standard non-coin telephone.
01 - Multi-party line, typically 4-party or 8-party service. The operator will come on to ask for the caller's telephone number.
02 - ANI failure. The operator will come on to ask for the caller's telephone number.
03-05 Not used.
06 - Used for multiple customers from the same telephone number, such as in hotels where they do not also automatically identify the room number.
07 - This caller requires special handling by an operator. Where this cannot be accomplished, the caller is given a recording telling them their call could not be completed.
08-19 Not used or reserved for specialized functions.
20 - Used by PBX systems where the caller is dialing out using the main number rather than, say, a specific number assigned to that station on that PBX.
21-22 Not used.
23 - Status as to whether caller is using a coin telephone or non-coin telephone cannot be determined.
24 - A call from a non-coin telephone to a toll-free number has been converted to its regular telephone number.
25 - A call from a coin or prison telephone to a toll-free number has been converted to its regular telephone number.
26 - Not used.
27 - Network signalling controlled coin telephone.
28 - Not used.
29 - Call from a prison telephone (which usually only allow 0+ collect service).
30 - Call to an unassigned number that is to be routed to a recording.
31 - Call to an assigned number that has been manually placed out of service.
32 - Call to a recently disconnected number.
33 - Not used.
34 - Operator assisted call that billing has been completed.
35-39 Not used.
40-49 Reserved for local use by carrier. 50-51 Not used.
52 - Outward WATS call.
53-59 Not used.
60 - Non-coin caller using a TRS (transport provider).
61 - Call from PCS/Cellular system user over Type 1 trunk.
62 - Call from PCS/Cellular system user over Type 2 trunk.
63 - Call from PCS/Cellular system user who is roaming on another provider's network. Number is generally a temporary number assigned to that user while roaming on that network.
64-65 Not used.
66 - Caller from a hotel using a TRS (Transport provider).
67 - Caller from a restricted line using a TRS (Transport provider).
68-69 Not used.
70 - Coin telephone which is not network signalling controlled.
71-92 Not used or reserved for other uses.
93 - Call coming from a Private Virtual Network.
94-99 Not used.

Privacy note

It is very important to realize that, when calling a telephone number, your own telephone number and telephone line type (http://www.nanpa.com/number_resource_info/ani_ii_assignments.html) can always be captured by ANI equipment at the destination site -- whether or not you would otherwise be able to "block" transmission of your telephone number via Caller ID. ANI is unrelated to Caller ID, therefore Caller ID blocking does not affect the delivery of your telephone number to ANI service subscribers. The destination telephone company switching office will always know the originating telephone number, whether or not you have blocked Caller ID, or have a private number listing, and can relay that information to those who subscribe to ANI delivery services. Toll-free Inward WATS number subscribers and large companies normally have access to ANI information, either instantly via installed equipment, or via a monthly billing statement.

Bill collectors and private investigators have often conducted skip tracing of missing people by sending them postcards, enticing them to call their "800" numbers. The "skip" reveals his or her whereabouts by dialing the number. Residential subscribers can also obtain access to ANI information through third party companies that charge for the service.

Similar Services in Other Countries

• Europe: Calling Line Identification (CLI)
• UK: Caller Line Identification (CLID)