Caller ID (caller identification, CID, or aggrandized properly calling integer identification) is a telephone service, convenient on POTS lines, that transmits a caller's cipher to the called party's telephone equipment during the ringing Talking Caller ID signal, or when the call is being set up but before the call is answered. Where available, caller ID can also provide a denomination associated with the calling telephone number. The information trumped-up feasible to the called party may be manufactured visible on a telephone's own display or on a separate attached device.

The first booth trial for caller ID and other "TouchStar" admission was on July 7, 1984 in Orlando, Florida. Ellis D. Hill, the head of the BellSouth Product team, coined the term caller ID. This exchange trial lasted seven months. It was conducted and analyzed by Bell Labs/AT&T Network Systems. In 1987, Bell Atlantic conducted another market trial in Hudson County, Fresh Jersey, which was followed by delimited deployment. BellSouth was the first band to deploy caller ID in December 1988 in Memphis, Tennessee, with a full deployment to its 9-state region over the next four years. Bell Atlantic was the second local telephone convention to deploy Caller ID in Dissimilar Jersey's Hudson County. US West Communications (now Qwest) was the third local telephone body to afford caller ID service in 1989.