Patent ID: 8278839

Claim:
A two-wire switching circuit for controlling the power delivered from an AC power source to an electrical load, the switching circuit comprising: a mechanical air-gap switch adapted to be coupled in series electrical connection between the AC power source and the electrical load; a first turn-on delay circuit adapted to be coupled in series electrical connection with the mechanical air-gap switch when the mechanical switch is in a first position, the first turn-on delay circuit operable to conduct a control current through the mechanical air-gap switch when the mechanical switch is in the first position; and a first controllably conductive device having a control input and coupled in parallel electrical connection with the first turn-on delay circuit, the first controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load when the mechanical switch is in the first position, the first controllably conductive device operable to change from a non-conductive state to a conductive state in response to the first turn-on delay circuit after a first predetermined time from when the mechanical air-gap switch changes to the first position; and a second controllably conductive device having a control input and coupled in parallel electrical connection with the first controllably conductive device, the second controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load when the mechanical switch is in the first position, the second controllably conductive device operable to change from a non-conductive state to a conductive state in response to the first turn-on delay circuit after a second predetermined time from when the first controllably conductive device changes from the non-conductive state to the conductive state, the second controllably conductive device operable to stay latched in the conductive state; wherein the mechanical air-gap switch and the second controllably conductive device are operable to conduct the load current when the mechanical air-gap switch is in the first position.