Electronic Switching System

In telecommunications, an electronic switching system (ESS) is:

• A telephone exchange based on the principles of time-division multiplexing of digitized analog signals. An electronic switching system digitizes analog signals from subscriber loops, and interconnects them by assigning the digitized signals to the appropriate time slots. It may also interconnect digital data or voice circuits.
• A switching system with major devices constructed of semiconductor components. A semi-electronic switching system that hadreed relays or crossbar matrices for its talk paths, as well as semiconductor components, was also considered to be an ESS in the 20th century. 1ESS switch was a prominent example.

In the late 20th century most telephone exchanges were eliminated that were not time-division ones, so interest in this distinction became primarily historical. When the term is still used, it means approximately the same thing as Stored Program Control exchange