caller ID

For the protein involved in the synthesis of major histocompatibility complex II, see CLIP (protein). Caller ID (caller identification or CID, and more properly calling number identification—CNID) is a telephony  service that transmits the caller's telephone 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. The information made available to the called party is visible on a small liquid crystal display embedded on the telephone, or on a separate unit which is connected to the telephone.
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Noun
1. a small display that will show you the telephone number of the party calling you
(hypernym) display

A network service feature that permits the recipient of an incoming call to determine, even before answering, the number from which the incoming call is being placed.

(CID) A feature of some modems.