A single-pole lamp switch commonly used in the early twentieth century. It could control a single circuit or any number of circuits within its capabilities. When the knob (h) is turned to the right, and the connected spring (p) is wound as far as possible, the blade (k) is loosened from the contact tips (s) and thus breaks the circuit.
International Correspondence Schools A Textbook on Electric Lighting and Railways (Scranton, PA: International Textbook Company, 1901)
Courtesy the private collection of Roy Winkelman