Caller ID (CID), also called calling line identification (CLID), is a telephone service that transmits a caller's number to the called party's telephone equipment during the ringing signal, or when the call is being set up but before the call is answered. Caller ID can also provide a name associated with the calling telephone number. The information made available to the called party may be displayed on a telephone's display, on a separately attached device, or be processed by an attached computer with appropriate interface hardware.

Caller ID may be used to display a caller's telephone number (and, in association with a database, name) on a called user's telephone. This works in most countries; although systems are incompatible, each country will have appropriate equipment. A modem can pass CLID information to a computer for purposes of call logging or blocking, but this can be problematic as modems in different countries have different systems, causing hardware or software incompatibilities. However, many modems are designed and programmed to handle multiple signaling methods and can be configured to use the local standard.

You can upload your customer database to the Cooler Master PBX so that when your customers call you — even if they call you from their cell phone, their name will display on your Cool Telecom telephone.