EPABX / Intercom Systems



An Electronic Private Automatic Branch Exchange comes under the category of business phone systems which serve a business environment. Multi-line connections can be made through a single telephonic connection. It is an office equipment of immense use for telephonic connectivity with extensions of a single phone line. It is a business phone system for office communications.

It has proven to be of immense use in communicating within office, making routine work simpler. It can be defined as a switching system for calls that enables both internal as well as external switching functions in an organization. Typically up to 10,000 subscribers can be accommodated by a single EPABX system.

The numerous tasks that can be performed by EPABX are listed below:-

  • Auto Attendant.
  • Automatic call distributor and ring back facility.
  • Automated directory services (where callers can be routed to a given employee by keying or speaking the letters of the employee’s name)
  • Call accounting.
  • Call forwarding on absence or when busy.
  • Call pick-up and transfer.
  • Call waiting.
  • Conference call and 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)
  • Shared message boxes (where a department can have a shared voicemail box)
  • Voice mail.
  • Voice paging (PA system)

Components of EPABX are:-

  • Internal switching network.
  • Microcontrollers and microcomputer for arbitrary data processing for control and the logic.
  • Logic cards, switching and control cards, power cards and related devices to facilitate operation.
  • Stations or telephone sets, sometimes called lines.
  • External Telco trunks that deliver signals to and from the EPABX.
  • Console or switchboard allows the operator to control incoming calls.
  • UPS, connecting wiring, cabinets and other housing materials.

The selection of an EPABX must be carefully done based on a detailed study of the traffic flow and needs of the office. They make communication within office easier and hence become a requisite as a business phone system in an office environment.

An intercom (intercommunication device), talkback or door phone is a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network. Intercoms are generally mounted permanently in buildings and vehicles. Intercoms can incorporate connections to public address loudspeaker systems, walkie talkies, telephones, and to other intercom systems. Some intercom systems incorporate control of devices such as signal lights and door latches.There are simple house intercoms and intercoms developed for collective apartments. Some are equipped with video facilities also.

Permanent Systems

Traditional intercoms and public address systems are composed entirely of analogue electronics components but many new features and interfacing options can be accomplished with new intercom systems based on digital connections. Video signals can be carried as well as voice.

Many schools and office buildings now use audio / video systems to identify visitors trying to gain access to a locked building, and can be interfaced with the building’s access control system. Intercom systems can be found on many types of vehicles including trains, watercraft, aircraft and armoured fighting vehicles.

Portable Systems

Portable intercoms are commonly used by special event production crews and professional sports teams. performing arts venues such as theaters and concert halls often have a combination of permanently mounted and portable intercom elements. Motorsports race tracks often have both portable and permanent intercom stations mounted at critical points around the racecourse for use by race officials and emergency medical technicians.

In general, a residential intercom has two normal functions:-

1) To page another person for short information conversations. For instance, “Hi you are wanted on the phone.” “Okay, I’ll be right there.”

2) Monitoring a room to make it easier to move around the office or home and still be able to monitor the activities in that room. More advanced systems have become popular as a result of added features such as music distribution, door chimes, more versatility and better overall performance.