An off-premises extension (OPX), sometimes also known as off-premises station (OPS), is an extension telephone at a location distant from its servicing exchange. One type of off-premises extension, connected to a

private branch exchange A business telephone system is a telephone system typically used in business environments, encompassing the range of technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone system differs from ...

(PBX), is generally used to provide employees with access to a company telephone system while they are out of the office. Off-premises extensions are used in distributed environments, serving locations that are too far from the PBX to be served by

on-premises wiring On-premises wiring (customer premises wiring) is customer-owned transmission or distribution lines. The transmission lines may be metallic (copper) or optical fiber, and may be installed within or between buildings. Premises wiring may consis ...

. Another type of off-premises extension, connected to a public telephone exchange, is generally used to allow a private phone line to ring at a second location. For example, the owner of a business may have an OPX for their home phone at the business location, allowing them to avoid missing calls to the home phone. Telephone service providers charge a significant monthly rate for an OPX, partly calculated by the distance; in extreme cases, the distance may result in a rate higher than simply having an additional central office line with its own number. Recent innovations such as call forwarding-no answer or simultaneous ringing of multiple lines can replace several of the conveniences of an OPX at much lower cost. An OPX uses a conditioned wire pair that is usually used only for voice applications, while for data, a pair usually needs to be unconditioned. An alarm circuit is an unconditioned pair. In

Internet telephony Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

, a

VoIP VPN A VoIP VPN combines voice over IP and virtual private network technologies to offer a method for delivering secure voice. Because VoIP transmits digitized voice as a stream of data, the VoIP VPN solution accomplishes voice encryption quite simply, ...

OPX may be implemented by connecting an extension over a virtual private networking connection, instead of connecting it directly to the

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

. As a host connected by a VPN appears as a part of the local area network, the off-premises extension appears to the IP-PBX as if it were on-site.

References

{{reflist Communication circuits

See also

References