two-motion selector

A lifting rotary selector is an electromechanical component invented by the American Strowger for telephone exchanges, in which a switching arm was first raised by a certain number of steps and then swung in with another series of pulses to a contact arranged in a circular path.

or In general, these selectors were of decimal construction, each ten steps up and 10 x 10 contacts in the ten levels, so that a total of 100 connections could be switched. These rotary selectors were the standard component of telephone exchanges for many decades, some of them still are today and are only gradually disappearing with the introduction of electronic exchanges.