A PBX is an older-type telephone system that uses circuit switching. They are also
referred to as proprietary PBXs. Circuit switching saves a path for each voice conversation.
Although these types of systems are no longer manufactured, many are still in
use. Each PBX manufacturer uses proprietary signaling to link telephone and trunk
lines to the CPU. Features and peripherals such as contact center software also operate
on proprietary signaling. In PBXs that support a single building, the components are
generally housed in one cabinet. The main components of a proprietary PBX are the
CPU and circuit packs for dial tone, touch-tone, and other signals. Other ports connect
to trunks, individual telephones, and voicemail.
