Essexߞa continuing research experiment in time-separation communication

A brief history of the research programme in electronic switching outlines the events which led to ´Essex´ (Experimental Solid-State Exchange), a time-separation communication system experiment. The organization of the laboratory system, which combines remote line concentration, time-separation switching, and p.c.m. transmission, all implemented by solid-state devices, is reviewed. Variations in organization which provide greater flexibility are discussed. Facilities for conventional ringing and dialling have been added to the laboratory model. New solid-state circuits which use fewer components and less power and a new encoder with a built-in compression characteristic have been tested in the model. These recent changes are described.