Traditional, Private Branch Exchange (PBX) telephone systems have changed a lot since the spread of the internet. Slowly but surely, businesses are phasing out analogue systems and replacing them with IP PBX alternatives.
A traditional PBX system features an exchange box on the organizations premises where analogue and digital phones connect alongside external PSTN/ISDN lines from the telecommunication company. It gives the company full ownership, but is expensive to setup and most frequently requires a specialist technician to maintain, repair and make changes.