Electronic switching system

In telecommunications, the term electronic switching system (ESS) has the following meanings:

A telephone switching system based on the principles of time-division multiplexing of digitized analog signals. An electronic switching system digitizes analog signals from subscribers' 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 has reed relays or crossbar matrices, as well as semiconductor components, is also considered to be an ESS.