3 Position Switch for Electric Hose.  Side to side switch has 3 postions on/off/on.   One position turns on the suction, the middle turns everything off, and the other turns on the suction and powerhead.  

Brands using this switch on hoses include but no limited to:

BEAM

Electrolux

Duovac

Cana-Vac

Hoover

and more.