These days, the telephone number of the caller travels ahead of most calls. This is known as Calling Line Identity (CLI) or by BT as Caller ID.
What Is Calling Line Identity (CLI or CLID)?
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You will probably most often see this when someone calls your mobile phone. This is also known in the USA as Automatic Number Identification or ANI.
This number can be used by CTI software to match up to a computer record for that caller.
Author: Robyn Coppell
Published On: 2nd Feb 2023 - Last modified: 12th Aug 2025
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