A business phones system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key business phones system (KTS) to the private branch exchange (PBX).A business phones 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 telephone 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 business phones systems, and private branch exchanges, but many hybrid systems exist.
A key telephone system was originally distinguished from a private branch exchange in that it did not require an operator or attendant at the switchboard to establish connections between the central office trunks and stations, or between stations. Technologically, private branch exchanges share lineage with central office telephone systems, and in larger or more complex systems, may rival a central office system in capacity and features. With a key telephone system, a station user could control the connections directly using line buttons, which indicated the status of lines with built-in lamps.
Business telephone is a system where multiple telephones are used by businesses in an interconnected fashion that allows for features such as call handling and transferring, conference calling, call metering and accounting, private and shared voice message boxes, etc. A business telephone system can range from just a few phones in a small business up to a complex private branch exchange (PBX)system utilized by large businesses.
Business phone systems can function over the Public Switched Telephone Network (PSTN) and/or over the Internet (Internet telephony or VoIP). Business telephone systems can also be delivered as a hosted service (typically referred to as a centrex), which can free companies from having to invest in costly equipment.