5ESS Switch

The 5ESS Switch is the class 5 electronic switching system sold by Lucent Technologies (Formerly known as Western Electric, or WECO) . The 5ESS Switch is the digital central office circuit switching system many communication service providers use. 5ESS service first appeared in Seneca, Illinois (815 Area Code) back in 1982. It's one of the faster switches, and is used in a fair portion of the US. The 5ESS is primarily UNIX-based. When logged into the system, it fearures an assortment of "Channels", such as TEST channel and Maintenance channel. 5ESS runs on a TST (Time-Space-Time) topology, and the TSIs (Time Slot Interchangers) sport their own processors, increasing switch speed.

Some of this information taken from http://www.alleged.com/telephone/5ESS/