The introduction of digital switching in the 1960s

The Empress digital tandem exchange was designed and constructed in the UK Post Office (PO) Research Laboratories, it was experimental and had limited objectives. Basically, it was to demonstrate that digital switching, involving time slot changing was a practical proposition using the technology which was then available. It was also designed to show that the high speed low energy technology could be operated in close proximity to Strowger equipment without suffering interference from the electric and magnetic fields and finally to determine whether the exchange could be maintained by staff normally involved with electro-mechanical equipment. Considerable testing was carried out in the laboratory to settle the question of interference and the exchange was finally installed in the apparatus room of a Strowger exchange.