ANI: Automatic Number Identification

From Wikipedia, ANI is defined as follow:

“Automatic number identification is a feature of telephony intelligent network services which permits subscribers to display or capture the telephone numbers of calling parties.”

A “super” Caller ID that is used by the emergency services, Toll Free providers, and by telcos for billing purposes. It cannot be blocked and can be spoofed, but is not usually made available to consumers except by accident.

Location-Based Routing

One application of ANI is to determine the location of the caller using the phone number. Based upon this information, calls can be routed by the phone system to a specific agent group or can be transferred to an organization that specializes in the needs of the caller from that specific region or city.

IVR systems employ ANI when routing calls and when displaying caller information using Screen Pop.

Note: Seems to be more of an American term, but BT have something similar.