PBX

History

Historically a PBX was a company's manual switchboard, and was known as a PMBX (Private Manual Branch eXchange). These were gradually replaced by automated electromechanical and then electronic switching systems, called PABXs (Private Automatic Branch eXchange). As PMBXs are almost unheard of these days, the terms PABX and PBX have become synonymous. When PABXs were built using solid state and digital components the term EPABX came into use but PBX is still more widely recognized. The PBX term was dominant for so long, that it is now being applied very liberally to systems providing complex services regarding telephony, even if they are not Private, Branches or eXchanging anything.

PBXs were distinguished from smaller "key systems" by the fact that external lines are not normally indicated or selectable at an individual extension. From a user's point of view calls on a key system are made by selecting a specific outgoing line and dialing the external number; calls on a PBX are made by dialing the escape code (usually 9, 0 in some systems) followed by the external number; an outgoing trunk line is automatically selected upon which to complete the call. This practice is becoming obsolete as number analysis systems have been changing with modern technology - you can use internal numbers or external numbers without any need for escape codes.

posted by Jack @ 10:29 PM