Business telephony
Direct inward dialling
Direct inward dialling gives each internal extension of an organisation its own public number, reachable without going through the switchboard.
The organisation receives a block of consecutive numbers from its operator. The network passes the dialled number to the PBX, which routes the call to the right extension. The direct numbers of staff, departments or fax lines are DID numbers, even though they share the same physical access.
Why it matters for fax
Direct inward dialling makes it possible to give each department, or even each person, a separate fax number without multiplying lines or machines. Combined with a fax server, it automatically delivers each incoming fax to its recipient.