PBX (Private Branch Exchange) telephony is a traditional type of phone system that allows multiple people to make phone calls at the same time without having to go through a switchboard operator. They are generally used by medium to large businesses, and have the ability to establish a phone connection, maintain the call for as long as needed, disconnect the connection when finished, and provide basic information such as the length of the phone call.
The most important component of PBX telephony is the logic processor, which handles all of the call routing for the system. They also require outside telco trunks to send and receive the audio signals, as well as a microcomputer to perform data processing. In addition, most PBX systems have a protected power supply so they can stay operational in the event of a blackout or sudden power surge.
PBX telephony originally required special phones in order to function, but they are now compatible with almost every type of phone on the market. Most of the systems also have between two to eight standard phone lines, and another four to eight extensions for analog or IP phones. This capacity can typically be extended for an additional cost. The standard interface for the system tends to be either a two-wire interface, a proprietary protocol, or DECT for cordless phones.
The primary advantage for PBX telephony is the greatly reduced cost of internal phone calls. All of the circuit switching occurs within the system, so the business doesn’t have to pay the normal charges for local phone service. They also provide access to special features such as conference calls, call forwarding, voice mail, and caller ID which may be useful to companies.