Infinite switch

Like the modern infinite switch, Hall's invention used a bi-metallic strip, heated by a constant current, to break a connection after a given period of time.

However, unlike its successors, Hall's invention was not self-resetting and would only stay on for a single cycle, after which a manual reset button could be pressed.

[2] The infinite switch itself was described in a 1975 patent of George F. Esker Jr. and Otto J. Cousins of the Harper Wyman Company.

[3] A rotary hand control turns a shaft that is connected within the infinite switch to a cam and follower.

At the maximum heat position the cam follower applies sufficient force for the cycling contacts to remain closed at all times.

The force from the heated bimetallic strip increases as its temperature rises until it overcomes the combined force from the cam follower, an unheated bimetallic strip that compensates for ambient temperature, and the permanent magnet allowing the cycling contacts open which interrupts the electric current to both heating elements.

The preceding discussion referring to two cycling contacts presumes the parallel or voltage sensitive type.

This has the effect of shrinking the range of power delivered by the voltage sensitive type when the heating element is cooled, by a vessel containing water for example.

The pulse of radio frequency noise emitted by any electrical arc is contained within the metal enclosure required for a safe design in the event of a component or wire insulation failure.