automatic number identification (ANI)
1. A service feature in which the directory number or equipment number of a calling station is automatically obtained.
Note: ANI is used in message accounting.
2. The code that provides the billing number of the line or trunk that originated a call. [T1.104-1988]
3. A system that identifies the billing account for a call. For 911 systems, the ANI identifies the calling party and may be used as a call back number. [47CFR]