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Strowger switch

"SXS" redirects here. For the flash memory standard, see SxS. For the Microsoft Windows SxS, see Side-by-side assembly. For the Side by Side all terrain vehicle, see Side by Side (UTV).
Western Electric 7A Rotary, friction drive (Bird-cage), No. 7001 Line Finder. Note the driven bevel gear on the right-hand side; this type has a steady rotary motion and does not employ an electromagnet for stepping.
Bank of two-motion switches

The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1891 by Almon Brown Strowger. Because of its operational characteristics, it is also known as a step-by-step (SXS) switch.

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