A telephone system is a group of telephone exchange equipment in a centralized location. The purpose of this system is to make calls to and from a number of phone lines on a consistent basis. PBX systems also permit those making the calls to stay in touch with each other, to add extensions and modifications to the system, and to customize the ringtones and notification tones that accompany the various telephone calls.
PBX stands for Private Branch Exchange and it is used to route calls from one telephone exchange to another. The term is pronounced play-pay.
PBX systems have been around since the 1960s, when they first made their appearance on military aircraft, and were first built into the architecture of a home or business telephone line starting in the mid-1980s.
A PBX is a system consisting of a central location for making calls, separate calling cards for each individual telephone line, and a card-switching cabinet with one or more switches that allow the user to switch from one line to another. All of these components are interconnected in such a way that calls can be made from a single line to a variety of other lines. An answering machine system is also an integral part of the PBX. It serves as a central listening post for incoming calls on a single line.
Adding additional phones to the system can be done by having a central location where staff can install or service new lines. These central locations are often called installations, switchings, or just switches.
(1) switches: these are the original components of a PBX phone system, usually housed in racks of modular cabinets. They are used to manage the connection between telephone lines. They are commonly made of plastic and can be placed at the end of a phone line, or in the cabinet of a central location, such as a business center.
(2) card-switches: these are box-shaped devices that contain multiple function buttons and a power supply for a special phone line. Card-switches are often used in conjunction with switches to allow the user to dial a phone number by pushing the relevant button on the device.
(3) extension: extension devices are intended for a particular telephone line. They usually connect to one another using telephone plug-ins.
(4) voicemail: voicemail is the system by which the user can set up and control his/her voicemail. This function is often incorporated into answering machines and call centers.
(5) intercom: intercom is a dedicated telephone line. Its use enables one telephone line to be linked to another using voice connectors. There are various types of intercom devices, such as those for the office and those for the home.
(6) sound: this is an optional component of an intercom system that creates a sound from the mouthpiece of the speaker. It may also have other functions, such as the ability to vibrate.
(7) intranet: this is a set of computers (either network-based or local) which link to a telephone system, thereby allowing each telephone line to have a connection to each other telephone line.