What is "caller id"

alt. 1 (context countable English) The telephone number and/or name of the originator of an incoming telephone call, displayed on the screen of the telephone or other electronic device receiving the call. 2 (context uncountable English) The service of providing such information, sometimes included in one's standard telephone contract and sometimes available for an extra fee. n. 1 (context countable English) The telephone number and/or name of the originator of an incoming telephone call, displayed on the screen of the telephone or other electronic device receiving the call. 2 (context uncountable English) The service of providing such information, sometimes included in one's standard telephone contract and sometimes available for an extra fee.

n. a small display that will show you the telephone number of the party calling you

Caller ID (caller identification, CID), also called calling line identification (CLID), calling number delivery (CND), calling number identification (CNID) or calling line identification presentation (CLIP), is a telephone service, available in analog and digital phone systems and most voice over Internet Protocol (VoIP) applications, that transmits a caller's number to the called party's telephone equipment during the ringing signal, or when the call is being set up but before the call is answered. Where available, Caller ID can also provide a name associated with the calling telephone number. This service is called CNAM. The information made available to the called party may be displayed on a telephone's display, on a separately attached device, or personal computer.

Caller ID information typically consists of the caller's telephone number while CNAM consists of the caller's name. A modem can pass CLID information to a computer for purposes of call logging or blocking, but this can be problematic as modems in different countries have different systems, causing hardware or software incompatibilities. However, many modems are designed and programmed to handle multiple signalling methods, and can be configured to use the local standard.

Caller ID may be used by the recipient to avoid answering unwanted incoming calls by the concept of informed consent; however, it also poses problems for personal privacy. The possibility of caller ID spoofing may render received information unreliable.