What are the different types of private branch exchange (PBX) systems?
A PBX is the standard telephony system used in enterprises and is fairly common among small and medium-sized businesses. A PBX is known as a switched system, providing a centralized infrastructure for telephony. This allows for a consistent environment for all employees with access to the PBX, such as common features and an internal dialing plan with user-assigned extensions. From an IT perspective, the PBX allows for centralized control and management across the system.
Prior to the advent of Internet Protocol (IP), there really was just one type of PBX. The other options to a premise-based system would be a key telephone system or a central office exchange service (Centrex). The former is a scaled-down PBX, more suitable for smaller businesses with simpler needs. Centrex has long been a staple of campus environments that need PBX-like capabilities, but at a lower cost in the form of a hosted system that is leased rather than owned.
With IP now becoming the standard for telephony, the PBX has evolved into the IP PBX. Legacy PBX systems still account for most of today's installed base, but the vast majority of new purchases and upgrades are IP PBX. The systems are similar at their cores, but IP-based systems are less capital-intensive and offer more flexibility in terms of adding new features and integrating VoIP with other communication modes.