Caller ID (caller identification, CID), also called calling line identification (CLID), Calling Line Identification (CLI), calling number delivery (CND), calling number identification (CNID), calling line identification presentation (CLIP), or call display, is a telephone service, available in analog and digital telephone systems, including Vo IP, that transmits a caller's telephone number to the called party's telephone equipment when the call is being set up.The caller ID service may include the transmission of a name associated with the calling telephone number, in a service called CNAM.If the name does not exist, then the city, State, Province, or other designation may be sent.Some of these databases may be shared among several companies, each paying every time a name is "extracted".For example, the caller's name may be datafilled in the originating switch, in which case it is sent along with the number.
These original and historic working models are still in the possession of Paraskevakos.
The idea of CNID as a service for POTS subscribers originated from automatic number identification (ANI) as a part of toll free number service in the United States. ANI was originally a term given to a system that identified the telephone number placing a call, in a non-electronic central office switch.
Previous to this, the calling number could not be identified electronically.
CLI localisation describes the process of presenting a localised CLI (Calling Line Identity) to the recipient of a telephone call.
CLI localisation is utilised by various organisations, including call centres, debt collectors and insurance companies.