Calling Line Identity. Most UK inland telephone exchanges are able to send the caller`s number when a call is made. This feature is not always present on calls from mobile phones or overseas calls.
Found on http://www.encyclo.co.uk/visitor-contributions.php
Caller Line Identification. A service that allows you to find out the number of the caller by dialing 1471. If you have the appropriate equipment you may also be able to see the number of the caller before answering the call.
Found on http://www.encyclo.co.uk/local/20603