Caller line identification

In the UK and some other countries, caller line identification (CLI) is a feature provided by the public telephone network that transmits the telephone number of the caller to the recipient. The recipient may buy a telephone that displays the number, or may dial a service code to hear an automated voice read the number of the last caller. Networks usually allow the caller to enable or disable this service at will. Many Internet service providers (ISPs) providing dial-up access require the customer to use CLI to prevent abuse of the account by unauthorised callers.

A similar system used in the USA is called automatic number identification.