"In electrical controls, a stepping switch or uniselector (UK), also known as a stepping relay, is an electromechanical device which allows an input connection to be connected to one of a number of possible output connections, under the control of a series of electrical pulses.It can step on one axis (called a uniselector), or on two axes (a Strowger switch). Stepping switches were invented by Almon Brown Strowger in 1888."@en . . . .