EPABX (Electronic Private Automatic Branch Exchange) : A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. PBXs are also referred to as PABX – private automatic branch exchange and EPABX.

The electronic private automatic branch exchange (EPABX) is equipment that has made day-to-day working in the offices much simpler, especially in the area of communication. The EPABX may be defined as a switching system that makes available both internal and external stitching functions of any organisation.The selection of an EPBAX is a difficult task and requires deep knowledge of traffic pattern of the office. By using an EPABX both the internal and external needs of the organisation are fully served. With the advent of powerful microprocessors and advancements in the field of computers, the EPBAX can boast of versatile features. Hotline can be established between the boss and his immediate subordinates.

The feature of a call transferring and forwarding is another area enabling mobility of the users. Autoconferencing and automatic redialling of numbers found engaged on the first trial are some of other advancements in the features of the EPBAX.

public address system (PA system)

A public address system (PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution.

Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with many speakers are widely used to make announcements in public, institutional and commercial buildings and locations—such as schools, stadiums, and passenger vessels and aircraft. Intercom systems, installed in many buildings, have both speakers throughout a building, and microphones in many rooms so occupants can respond to announcements.

PA over IP

PA over IP refers to PA paging and intercom systems that use an Internet Protocol (IP) network, instead of a central amplifier, to distribute the audio signal to paging locations across a building or campus, or anywhere else in the reach of the IP network, including the Internet. Network-attached amplifiers and intercom units are used to provide the communication function. At the transmission end, a computer application transmits a digital audio stream via the local area network, using audio from the computer's sound card inputs or from stored audio recordings. At the receiving end, either specialized intercom modules (sometimes known as IP speakers) receive these network transmissions and reproduce the analog audio signal. These are small, specialized network appliances addressable by an IP address, just like any other computer on the network .