Business telephone system

PBXprivate branch exchangePABXkey telephone systemHosted PBXPBXsFollow-mePBXeskey phone systemPBX Systems
A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX).wikipedia
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1A2 Key Telephone System

1A2 Key System1A21A2 key systems
The systems marketed in North America as the 1A, 6A, 1A1 and the 1A2 Key System are typical examples and sold for many decades.
The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System.

Trading turret

Turrets
These systems commonly have their front end units referred to as Turrets and are notable for their presentation of hoot-n-holler circuits.
A trading turret or dealer board is a specialized telephony key system that is generally used by financial traders on their trading desks.

Telephone exchange

exchangescentral officeexchange
Before the advent of large-scale integrated circuits, key systems were typically composed of electromechanical components (relays) as were larger telephone switching systems. From the 1960s, a simulated PBX, known as Centrex, provided similar features from the central telephone exchange.
For corporate or enterprise use, a private telephone exchange is often referred to as a private branch exchange (PBX), when it has connections to the public switched telephone network.

Caller ID

caller line identificationCaller-IDCalling Line Identification
A call placed behind a private branch exchange (PBX) has more options.

Extension (telephone)

extensionextensionstelephone extension
Each device connected to the PBX, such as a telephone, a fax machine, or a computer modem, is referred to as an extension and has a designated extension telephone number that may or may not be mapped automatically to the numbering plan of the central office and the telephone number block allocated to the PBX.
Some telephones intended for use as extensions have built in intercom features; a 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.

IP PBX

IP-PBXIPBX
Since the advent of Internet telephony (Voice over IP) technologies, PBX development has tended toward the IP PBX, which uses the Internet Protocol to carry calls.
An IP PBX ("Internet Protocol private branch exchange") is a system that connects telephone extensions to the public switched telephone network (PSTN) and provides internal communication for a business.

Centrex

Integrated Business Network
From the 1960s, a simulated PBX, known as Centrex, provided similar features from the central telephone exchange. In wireline telephony, the original hosted PBX was the Centrex service provided by telcos since the 1960s; later competitive offerings evolved into the modern competitive local exchange carrier.
It provides functions similar to a PBX, but is provisioned with equipment owned by, and located at, the telephone company premises.

Line hunting

hunt grouphunt groupsMulti-line hunting
As PBX systems gained popularity, they began to feature services not available in the public network, such as hunt groups, call forwarding, and extension dialing.
Hunt groups are supported by some PBX phone systems.

AT&T Merlin

MERLINAmerican Bell Merlin
One of the most recognized such systems is the AT&T Merlin.

Switchboard operator

telephone operatoroperatortelephonist
The term PBX originated when switchboard operators managed company switchboards manually using cord circuits. Originally having started as an organization's manual switchboard or attendant console operated by a telephone operator or just simply the operator, PBXs have evolved into VoIP centers that are hosted by the operators or even manufacturers.
As well as the people that were employed by the public networks, operators were required at private branch exchanges (PBX) to answer incoming telephone calls and connect them to the correct extension.

Telephone numbering plan

Area codeTelephone codearea codes
Each device connected to the PBX, such as a telephone, a fax machine, or a computer modem, is referred to as an extension and has a designated extension telephone number that may or may not be mapped automatically to the numbering plan of the central office and the telephone number block allocated to the PBX.
Many organizations have private branch exchange systems which permit dialing the access digit(s) for an outside line (usually 9 or 8), a "1" and finally the local area code and xxx xxxx in areas without overlays.

Public switched telephone network

PSTNpublic telephone networktelephone network
Early electronic key systems used dedicated handsets which displayed and allowed access to all connected PSTN lines and stations. For the option to call from IP network to the circuit-switched PSTN (SS7/ISUP), the hosted solutions include interconnecting media gateways.
There are also private networks run by large companies which are linked to the PSTN only through limited gateways, such as a large private branch exchange (PBX).

Telephone switchboard

switchboardswitchboardscentral switchboard
Originally having started as an organization's manual switchboard or attendant console operated by a telephone operator or just simply the operator, PBXs have evolved into VoIP centers that are hosted by the operators or even manufacturers.
A private branch exchange (PBX) in a business usually has an attendant console for the operator, or an auto-attendant, which bypasses the operator entirely.

Voice over IP

VoIPVoice over Internet Protocolvoice-over-IP
Since the advent of Internet telephony (Voice over IP) technologies, PBX development has tended toward the IP PBX, which uses the Internet Protocol to carry calls. Originally having started as an organization's manual switchboard or attendant console operated by a telephone operator or just simply the operator, PBXs have evolved into VoIP centers that are hosted by the operators or even manufacturers. The modern key system is usually fully digital, although analog variants persist and some systems implement VOIP services.
In 2008, 80% of all new Private branch exchange (PBX) lines installed internationally were VoIP.

Session Initiation Protocol

SIPSession Initiation Protocol (SIP)SIP (Session Initiation Protocol)
The modern key system now supports SIP, ISDN, analog handsets (in addition to its own proprietary handsets - usually digital) as well as a raft of features more traditionally found on larger PBX systems.
The service provides routing of telephone calls from a client's private branch exchange (PBX) telephone system to the public switched telephone network (PSTN).

Competitive local exchange carrier

CLECcompeting carrierCompetitive Local Exchange Carriers
In wireline telephony, the original hosted PBX was the Centrex service provided by telcos since the 1960s; later competitive offerings evolved into the modern competitive local exchange carrier.
Initially, they offered a "shared PBX" service with these switches and interconnected with the ILECs as end users rather than as co-carriers.

Signalling System No. 7

SS7Signaling System 7Signalling System 7
For the option to call from IP network to the circuit-switched PSTN (SS7/ISUP), the hosted solutions include interconnecting media gateways.
This is the case for earlier analogue trunks, multi-frequency (MF) and R2 digital trunks, and DSS1/DASS PBX trunks.

Call parking

Call parkpark
Call park is a feature of some telephone systems that allows a person to put a call on hold at one telephone set and continue the conversation from any other telephone set.

Automated attendant

auto attendantauto-attendantphone tree
Typically the auto attendant is included in a business's phone system such as a PBX, but some services allow businesses to use an AA without such a system.

Direct inward dial

Direct Inward Dialingdirect inbound dialingDDI
Direct inward dialling (DID), also called direct dial-in (DDI) in Europe and Oceania, is a telecommunication service offered by telephone companies to subscribers who operate a private branch exchange (PBX) system.

Voicemail

voice mailvoice-mailvoice messaging
Apart from offering advanced features (like voicemail), the system could also use a VoIP gateway to connect to traditional PSTN lines.
Most cell phone services offer voicemail as a basic feature; many corporate private branch exchanges include versatile internal voice-messaging services, and *98 vertical service code subscription is available to most individual and small business landline subscribers.

Automatic call distributor

automatic call distributionACDCall distribution
Private Branch Exchange (PBX) was a telephone exchange device that acted as a mini-switchboard to route phone calls.

Basic Rate Interface

BRIISDN BRI2B1D
Using small PBXs for ISDN is a logical step, since the ISDN basic rate interface provides two logical phone lines (via two ISDN B channels) which can be used in parallel.
The BRI ISDN service is commonly installed for residential or small business service (ISDN PABX) in many countries.

Answering machine

answering machinestelephone answering machineAnsafone

Night service (telephony)

Night service
Night service in telephony is a feature of private branch exchanges and other business telephone systems, whereby for a set period during the day (usually those hours outside of normal office or work hours, when normal operator services are not provided), all incoming calls are automatically redirected by the switchboard to a specific extension or to equipment such as an answering machine or other voice mail system.