What is a caller ID?

Caller ID is a telecommunication service that enables users to identify incoming calls before answering.

Caller ID is possible with mobile, analog, digital, and VoIP calls. 

Depending on the device being used, Caller ID displays on the device screen as a long number when the call connects. Caller ID is also used for caller identification when receiving text messages.

Users can store numbers on their devices using either the SIM card or the storage device’s memory. Keeping the number allows users to save the number under a recognizable name for quick recognition. This name is then displayed every time the stored number calls.

Caller ID works in two steps.

The first step is phone number identification. The number shown is the caller’s registered phone number. Landlines and mobile phones use this protocol, while calls from VoIP can be modified (information can be changed). This step allows easier referencing of call-back numbers.

Next is name identification, where the phone carrier of the receiving party identifies the caller’s name. This reference does not come from internal databases, as phone carriers use CNAMs to cross-reference the phone number with the suitable contact’s name.

CNAM, or Calling NAMe, is an outside telecom service companies use to pair incoming numbers with names. CNAMs are not centralized databases.