Central Exchange
Centrex is short for central exchange and has been used since the 1960's. Centrex is a PABX like solution for small businesses who do not want to invest in an inhouse phone system or the associated costs of maintaining it. This PABX like service is provided by the local Telephone company where in, the switching equipment resides at the central office (local Exchange). This service is delivered over the PSTN network with a few additional PABX like features that are programmed at the central office. Normal touch tone phones will work on the centrex network or in some cases special feature phones are available.
Just like a PABX, each line within the business group has an extension number in addition to its line number and calls can be made to lines within the group by calling the 3, 4 or 5 digit extension number. Calling other numbers outside the group will require a line access code of 1 or 9 just like a PABX. Centrex lines also have access to common PABX features such as call forward, do not disturb, voicemail, call pickup, camp on, call waiting, call hold, call transfer, etc. The Automatic call distribution (ACD) and Hunt groups can also be created for incoming calls.
These days, IP centrex is gradually replacing PSTN centrex where by the centrex service is delivered over data networks and end users are connected using IP devices over ethernet.
Just like a PABX, each line within the business group has an extension number in addition to its line number and calls can be made to lines within the group by calling the 3, 4 or 5 digit extension number. Calling other numbers outside the group will require a line access code of 1 or 9 just like a PABX. Centrex lines also have access to common PABX features such as call forward, do not disturb, voicemail, call pickup, camp on, call waiting, call hold, call transfer, etc. The Automatic call distribution (ACD) and Hunt groups can also be created for incoming calls.
These days, IP centrex is gradually replacing PSTN centrex where by the centrex service is delivered over data networks and end users are connected using IP devices over ethernet.