1. Acceptance of the concept
Before IP voice was commercially viable, millions of US SMEs were already using Centrex. In the early 1980s the US telecommunications market liberalised, creating 7 local operating companies (the equivalent of Openreach) nicknamed ‘Baby bells’. These all launched their own central exchange offerings (Centrex) in preference to on-premise telephone equipment. With a big stake in the equipment market, BT was never really interested in Centrex and the UK’s first Centrex product launched by Mercury in the early 1990s was clumsy, unreliable and expensive.