Telephone Networks
A private branch exchange (PBX) is a switch (more commonly called a switchboard) operated for one organization into which all telephone lines connect
A PBX is usually connected to the the telephone company’s end office
Telephone lines going from the PBX to the end office are usually called trunk lines if they are primarily devoted to
voice transmission from the switchboard
In data transmission the same circuits are referred to as leased circuits, private circuits, or dedicated circuits
Without a PBX each telephone must be connected to the telephone company’s trunk line, each phone has a separate telephone number, and a monthly connection fee (also no call forwarding).