History of PBX

Difference (from prior major revision) (minor diff, author diff)

Changed: 1c1

The Private Business eXchange (also called PBX or Private Branch Exchange) is a telephone switching center that is owned by a private business, compared to one that is owned by the common carrier or telephone company.

The Private Branch eXchange (also called PBX or Private Business Exchange) is a telephone switching center that is owned by a private business, compared to one that is owned by the common carrier or telephone company.

Removed: 6d5

Big PBX are sometimes interconnected by so called trunk lines.

Changed: 8c7,13

An aternative is to connect all the telephone sets to the PSTN, but the major disandvantage is that even internal calls would have to be payed.

For companies with multiple physical locations, PBXs are sometimes interconnected by so called trunk lines.

PBXs are distinguished from smaller "[key system]?s" by the fact that external lines are not normally indicated and selectable from an individual extension. From a user's point of view calls on a key system are made by selecting a line and dialing the external number; calls on a PBX are made by dialing 9 then the external number.

Another alternative is to connect all the telephone sets to the PSTN, but the major disandvantage is that every extension requires its own line (usually with a monthly recurring line charge); also, "internal" calls would be dialed externally, and charged for.

Finally, most local phone companies offer Centrex? or "Virtual PBX" service in which each extension has a trunk line are connected to the telephone company's [Central Office]?, where software on the CO switch enables PBX-like functionality.

Changed: 15,17c20,22

The are many PBX manufacturers.
Some of the most common include Agilent (was Lucent was AT&T), Siemens (includes Rolm), NEC, Toshiba, Fujitsu, Vodavi, Mitel.
All offer many capabilities, although each manufacturer may have a different name for each capability.

The are many PBX manufacturers. Some of the most common include: Agilent (was Lucent was AT&T), Siemens (includes Rolm), NEC, Toshiba, Fujitsu, Vodavi, Mitel, Ericson.

PBXs offer many capabilities, although each manufacturer may have a different name for each capability.

Changed: 19,28c24,33

- Direct Dialing (DDD or DDI), also called Direct Inward Dialing (DID)
- customised Abreviated dialing (Speed Dialing)
- follow-me
- call forwarding on absence
- call forwarding on busy
- call transfer
- music on hold
- automatic ring back
- night service
- call disribution (ACD,fixed sequences,...)

Changed: 31,32c36,37

- proprietary: the manufacter has defined a protocol. One can only connect the manufacturer's sets on the PBX
- standard interfaces: any device supporting the standard can be connected

Changed: 34c39

The most common digital standard for fixed devices is ISDN.

	Revision 7 . . (edit) December 16, 2001 12:40 pm by VincentV [link to ISDN, added Ericson in the manufacter short-list]
	Revision 6 . . December 14, 2001 5:03 am by (logged).75.42.xxx [Copyedit, add info. Key System. Centrex.]
	Revision 5 . . December 13, 2001 5:36 pm by (logged).253.39.xxx [merged content from PABX into PBX, copyedit]
	Revision 4 . . December 13, 2001 1:15 pm by (logged).15.135.xxx [Private Branch Exchange, other edits. Still needs cleanup.]
	Revision 3 . . December 13, 2001 9:21 am by (logged).132.130.xxx [A good overview of PBX world (please correct my english)]
	Revision 2 . . (edit) September 18, 2001 9:14 pm by Koyaanis Qatsi