Caller ID

from WordNet (r) 3.0 (2006)

caller ID
    n 1: a small display that will show you the telephone number of
         the party calling you

from The Free On-line Dictionary of Computing (8 July 2008)

Caller ID
CID

   <communications> (CID) A short piece of text transmitted by
   some telephone systems describing the origin of a call,
   e.g. the name of the caller.  Some telephone handsets can
   display this.  A {computer telephony integration} system might
   use it to trigger actions on the callee's computer such as
   looking up the caller in a database and displaying their
   details on screen.

   There may also be a separate "caller id number" giving the
   telephone number of the originator of the call.

   (2008-04-30)