Definition

• A PBX system is a type of telephone exchange, or system of electronic components used to connect telephone calls, which serves the needs of one office or building. Exchange areas in a telephone exchange are comprised of locations serviced by one telephone switch, or connection point. The exchange code used in telephone exchanges are the first three digits of the local number, not to be confused with the NPA, or three-digit area code. PBX systems also are referred to as EPABX (electronic private automatic branch exchange) and PABX (private automatic branch exchange) systems.
  
  

Connections

• PBX systems connect internal calls and PSTN (public switched telephone network) calls through the use of trunk lines. Trunk lines are transmission channels between a switching center and a node, or network connection point, which enables network access.
  
  

Benefits

• PBX systems utilize local circuit switching to reduce the cost of local calls. Many PBX systems feature services such as extension dialing, call forwarding and call holding.