Extension
What is Extension?
An extension is a short internal number — typically three to five digits — assigned to a person, department, or ring group on a PBX or cloud phone system, letting colleagues reach each other by dialing a short internal code instead of a full external phone number. A DID number can be mapped to an extension so external callers reach it directly, while internal calls between extensions never leave the phone system.
More detail
Extensions are usually assigned in logical blocks per department or location, making it easier for staff to remember and dial a colleague's number internally.
An extension is distinct from a DID: the extension is the internal dial-plan address, while a DID is the external phone number a caller outside the business actually dials to reach that same destination.
Frequently asked
- Is an extension the same thing as a phone number?
- No — an extension is a short internal code used to reach a colleague within the same phone system, while a phone number (or DID) is what an external caller dials; the two are commonly mapped together but serve different purposes.
- Can external callers dial an extension directly?
- Not the extension itself, but a DID number mapped to that extension lets an external caller reach it directly, or an auto-attendant can prompt callers to enter an extension to be routed internally.
See also
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