What is a withheld number?
    When a number is withheld, there is no caller ID, which means the recipient cannot see who is calling. A number can be withheld during digital, analogue or voice-over-IP (VoIP) telephone calls. The process of withholding a number is also called Calling Line Identification Restriction (CLIR). The recipient of a withheld number call usually sees a message such as “unknown” or “withheld number” in their phone display instead of a phone number.


    Further information

    Voice over IP: The Art of Switching from PSTN to IP

    What is VoIP?

    The Voice over Internet Protocol, also called IP telephony, is a method of communication for making calls over a broadband Internet connection as an alternative to regular calls made…

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