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DID (Direct Inward Dialing)

A phone number that routes directly to a specific extension or user, bypassing a receptionist.

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Direct Inward Dialing, usually shortened to DID, is a phone number that connects a caller straight to a particular person, desk, or endpoint inside an organisation instead of landing on a main switchboard.

DIDs are the basic unit of supply in modern business telephony. A VOIP provider buys blocks of DIDs from carriers and assigns them to customers, which is how a company can hand every employee their own direct number without buying a physical line for each one.

Because DIDs are frequently issued by VOIP providers rather than traditional carriers, a number that looks ordinary may be a DID sitting on an internet-based platform. That affects whether it can receive SMS, which is why line-type detection matters more than the number format.

  • SIP trunk — A virtual connection that carries voice calls over the internet instead of physical phone lines.
  • PSTN — The Public Switched Telephone Network — the traditional circuit-switched phone system.
  • Line type — The classification of a phone number as mobile, landline, VOIP, or invalid.

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