High gain relays and systems

Claim 1

A control circuit system comprising a relay operable at low power levels having an insulating base, stationary contact means mounted on said base, movable contact means mounted on said base for movement between a closed circuit position engaging said stationary contact means and an open circuit position spaced from said stationary contact means, spring means mounted on said base biasing said movable contact means from one of said positions to the other of said positions, and a metal wire secured between said movable contact means and said base, said wire being of a selected metal alloy to be deformed from an original length to a second length by said spring bias as said movable contact means is moved from said one position to said other position by said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to said original length and to display a relatively higher modulus of elasticity to move said movable contact means back to said one position against said spring bias when said wire is heated to said transition temperature, said wire having a selected cross-sectional size and length to be heated from room temperature to said transition temperature by passing electrical current through said wire with a power input of less than about 2 watts; a power source directing energizing current through said relay wire; a device to be energized from said power source through said relay contact means when said relay is in closed circuit position; and resistor means displaying varying resistance in response to temperature changes arranged to regulate said energizing current in said relay wire for operating said relay to energize said device at one temperature level and to deenergize said device at another temperature level.