This telephone pbx system architecture pdf has multiple issues. Unsourced material may be challenged and removed. Please update this article to reflect recent events or newly available information. 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 telephone systems, and private branch exchanges, but many hybrid systems exist. 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. A 1930s key telephone for a private branch exchange. Key telephone systems are primarily defined by arrangements with individual line selection buttons for each available telephone line.
Key systems can be built using three principal architectures: electromechanical shared-control, electronic shared-control, or independent key sets. New installations of key telephone systems have become less common, as hybrid systems and private branch exchanges of comparable size have similar cost and greater functionality. A typical rotary dial key telephone: the Western Electric eighteen-button Call Director, manufactured from 1958 to the early ’80s. 1930s and remained in use to the 1950s.
Introduced in 1953, 1A1 key systems simplified wiring with a single KTU for both line and station termination, and increased the features available. As the 1A1 systems became commonplace, requirements for intercom features grew. The original intercom KTUs, WECo Model 207, were wired for a single talk link, that is, a single conversation on the intercom at a time. The WECo 6A dial intercom system provided two talk links and was often installed as the dial intercom in a 1A1 or 1A2 key system. The 6A systems were complex, troublesome and expensive, and never became popular.
The advent of 1A2 technology in the 1964 simplified key system set up and maintenance. These continued to be used throughout the 1980s, when the arrival of electronic key systems with their easier installation and greater features signaled the end of electromechanical key systems. Two lesser-known key systems were used at airports for air traffic control communications, the 102 and 302 key systems. Western Electric equipment, but it did not gain the widespread use enjoyed by Western Electric equipment. Electronic shared-control systems led quickly to the modern hybrid telephone system, as the features of PBX and key system quickly merged.
Features could be added or modified simply using software, allowing easy customization of these systems. Into the 21st century, the distinction between key systems and PBX systems has become increasingly blurred. Effectively, the aspects that distinguish a PBX from a hybrid key system are the amount, scope and complexity of the features and facilities offered. Hybrid systems are a common tool in the financial services industry used on trading floors. These advanced hybrid key systems generally only require attached PBXs for interaction with back-office staff and voicemail.
Multiple Hoots are presented to multiple users over multiplexed speakers to multiple locations. PBX permits the shared use of these lines between all stations in the organization. Initially, PBX systems offered the primary advantage of cost savings for internal phone calls: handling the circuit switching locally reduced charges for telephone service via central-office lines. PBXs select the outgoing line automatically, or formerly, by an operator.