SWITCH

Switch in telecommunication often refers to a giant electronic switch in a telephone central office that routes telephone calls.  Just as a simple switch in your house can change the direction of electronic current, the term is also used to describe a complex telephone switching electronics unit that switches many many calls at the same time.

Unlike the simple switch that one may find inside a house, a telephone switch is often quite large.  It might consist of a number of "bays" of electronics, each of which stand about 6 feet fight and a few feet wide.  A telephone switch will often fill a good sized room.