Lets starts from the very begining....
The word PBX is some thing very nice to hear and very commenly hearing one..i heard first when i was in my degree days we had a paper there called Electronic communication...when i heard this first time did't got anything...when i came to know the expansion of it (PBX) Private Branch exchange......i got that it was some thing related to telephone exchange....someone told me that it is like an intercom....intercom..???oops..with god grace i don't know what is it on that time....
Later i got what really is ...An intercom (intercommunication device) is an electronic communications system within a building or group of buildings....it can called as phone with in a house or an office with out a external connection...(external connection means we have a group of telephone but don't have a connection from the telephone exchange)...and our groups of phone is interconnected...in computer terms we can call it as a Local Area telephone network or a LAN
