Definition of PBX System: Private Branch eXchange System. A PBX system, sometimes known as a phone switch or phone switching device, is a device that connects office telephones in a business with the public telephone network. PBX phones are phones or phone systems that utilize a PBX system. The initial central functions of a PBX system were to route incoming calls to the appropriate extension in an office, and to share phone lines between extensions. Over time, many functions have been added, such as automated greetings for callers using recorded messages, dialing menus, connections to voicemail, automatic call distribution (ACD), teleconferencing, and more.

Today, PBX phones are expected to handle a wide variety of duties beyond simple connection to the public phone system. The range of features offered by a PBX system varies, usually in proportion with the price of the equipment. Some of the main functions of PBX phones:

• Present a single business number that gives access to all company employees and departments
• Answer calls with a custom business greeting
• Offer a menu of options for directing the call, such as connecting to a specific extension or to a department
• Provide a directory of employee extensions accessible by inputting digits corresponding to employee first or last names
• Evenly distribute calls to a department among available employees through Automatic Call Distribution (ACD)
• Place callers on hold when they are waiting for an available department employee
• Play music or custom messages whenever callers are waiting on hold
• Take voice messages for any employee extension, for a department, or for the company in general
• Allow transfer of calls between extensions
• Conference multiple incoming calls with employee extensions
• Provide detailed call records and real-time system management

Of course, not every one of these features is available in all PBX phones. The hardest feature to provide has been Automatic Call Distribution (ACD), and usually vendors charge a premium for products that include this feature. Other features that often get left out include integrated voice messaging, conference bridging for conferencing multiple outside calls, and detailed real-time system monitoring. Many times some of these features are not part of the base PBX system but can be purchased through add-on system modules.

Diagram of Standard PBX >>