“Figs. 69 and 70 are inside and outside of the tumbler switch. The base of this switch is sometimes slate and sometimes porcelain. In larger switches, the “chopper” switch, which corresponds to the tumbler in small switches, is now the favourite, the cover being of metal and fitting over it.
The fixed contact pieces in this case are in the form of two small brackets held to the base by screws, and the moving contact consists of a sort of shoe fitted on the end of a bar of vulcanised fibre or vulcanite. The bar of insulating material is held at the other end in a metal cramp, which is pivoted between two pillars, as shown. The two pillars which support the pivot of the contact bar also carry a brass collar, the office of which is twofold.
It is screwed on its outside circumference, and on this screw the cover fits. It also forms a sort of guide for that portion of the apparatus which gives its name to the switch, and which operates it. This is a tumbling handle. When in the position shown in Fig. 69, the handle has tumbled forward, and has allowed the contact bar to obey the pressure of the straight spring shown behind, and its shoe to rise clear of the fixed contact pieces, thus breaking the circuit. To put the switch in the position of “On,” the handle is tumbled back, causing the other part of the bent lever of which it forms apart to force the contact shoe down between the fixed contact pieces.” (pp. 174 – 5)