Patent ID: 8841799

Claim:
An apparatus comprising: a plurality of normally-open manually operable switches; a first MOSFET having a first gate coupled to each switch of the plurality of switches, and a first source coupled to a high voltage potential terminal of a power source to receive electric power therefrom; a second MOSFET having a second source coupled to a low voltage potential terminal of the power source; a second drain also coupled to the first gate of the first MOSFET, and a second gate to receive electric power from the power source through at least the first source and a first drain of the first MOSFET; a plurality of third transistors each having a respective source coupled to the low potential terminal of the power source, a respective drain coupled to one of the switches of the plurality of switches, and a respective gate to receive a bias voltage through at least the first source and drain of the first MOSFET; and a controller coupled to the first drain and comprising a plurality of switch inputs, wherein each switch of the plurality of switches is coupled to a switch input of the plurality of switch inputs; and wherein closing one of the switches of the plurality of switches couples the first gate to the low potential voltage terminal of the power source through a corresponding one of the third transistors while the corresponding third transistor is in a conductive state, placing the first MOSFET into a conductive state, providing a high voltage potential through the first MOSFET to the second gate and to the controller, placing the second MOSFET into a conductive state, providing a low voltage potential to the first gate to latch the first and the second MOSFETs in a conductive state, and enabling the controller to latch the state of the plurality of switch inputs and to identify which one of the switches was closed, and placing the first MOSFET into the conductive state also provides the bias voltage through the first MOSFET to the gates of the plurality of third transistors, placing the third transistors into a non-conductive state, decoupling the switches from the low potential voltage terminal of the power source while the first MOSFET is in the conductive state.