Extension (telephone)

In residential telephony, an extension telephone is an additional

key telephone system for a small business may offer two to five lines, lamps indicating lines already in use, the ability to place calls on 'hold

' and an intercom on each of the multiple extensions.

In business telephony, a telephone extension may refer to a phone on an internal

direct inbound dialing

, if outside numbers are assigned to individual extensions.

An off-premises extension, where a worker at a remote location employs a telephone configured to appear as if it were an extension located at the main business site, may be created in analog telephony by using a leased line to connect the extension to the main enterprise system. Voice over IP makes the creation of off-premises extensions inexpensive and trivial as broadband Internet and virtual private networking can extend local network access anywhere in the world. In either system, an off-premises extension is reachable from within the same enterprise simply by calling its extension number directly; for inbound and outgoing calls, it functions as if it were located at the main place of business.

Reasons to use extensions

Since not all users dial out at the same time, sharing

private branch exchange

's call accounting to generate individualised long-distance bills for each room that are presented to the guest upon check-out.

References

^ Newton, H: Newton's telecom dictionary, CMP books, 2004, p. 901.

[1] Newton, H: Newton's telecom dictionary, CMP books, 2004, p. 901.