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Business Telephone System

A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging from small key systems to large-scale private branch exchanges.

A business telephone system differs from an installation of several telephones with multiple central office (CO) lines in that the CO lines used are directly controllable in key systems from multiple telephone stations, and that such a system often provides additional features related to call handling. Business telephone systems are often broadly classified into key telephone systems, and private branch exchanges, but many hybrid systems exist.

Hybrid key telephone system

Into the 21st century, the distinction between key systems and PBX systems has become increasingly blurred.

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. Their support for both analog and digital signaling, and of some PBX functionality gives rise to the hybrid designation.

A hybrid system typically has some call appearance buttons that directly correspond to individual lines and/or stations, but may also support direct dialing to extensions or outside lines without selecting a line appearance.

The modern key system is usually fully digital, although analog variants persist and some systems implement VOIP services. Effectively, the aspects that distinguish a PBX from a hybrid key system are the amount, scope and complexity of the features and facilities offered.

Private branch exchange

A private branch exchange (PBX) is a telephone exchange or switching system that serves a private organization and performs concentration of central office lines or trunks and provides intercommunication between a large number of telephone stations in the organization.

A PBX is differentiated from a key telephone system (KTS) in that users of a key system manually select their own outgoing lines on special telephone sets that control buttons for this purpose, while PBXs select the outgoing line automatically or, formerly, by an operator. The telephone sets connected to a PBX do not normally have special keys for central office line control, but it is not uncommon for key systems to be connected to a PBX to extend its services.

A PBX, in contrast from the key system, employs an organizational numbering plan for its stations. In addition the dial plan determines which digit sequences must be dialed to obtain access to a central office trunk. Modern number analysis systems permit users to dial internal and external telephone numbers without special codes to distinguish the intended destination.

Popular Call Features

  • Auto attendant
  • Auto dialing
  • Automated directory services (callers are routed to an employee by keying or speaking the letters of the employee's name)
  • Automatic call distributor
  • Automatic ring back
  • Busy override
  • Call blocking
  • Call forwarding on busy or absence
  • Call logging
  • Call park
  • Call pick-up
  • Call transfer
  • Call waiting
  • Camp-on
  • Conference call
  • Custom greetings
  • Customized abbreviated dialing (Speed dialing)
  • Direct inward dialing
  • Direct inward system access (DISA) (the ability to access internal features from an outside telephone line)
  • Do not disturb (DND)
  • Follow-me, also known as find-me: Routing of incoming calls. Calls received for a person, are routed to each number on a list for that person in turn until the call is answered or the list is exhausted (at which point the call may be routed to a voice mail system).
  • Interactive voice response
  • Music on hold
  • Night service
  • Public address voice paging
  • Shared message boxes (where a department can have a shared voicemail box)
  • Voice mail
  • Voice message broadcasting
  • Welcome message

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