Abstract: An electrical optical isolation circuit and device characterized by a light source, a light-sensitive sensor, and a variable shield between the light source and the light-sensitive sensor, the variable shield being adjustable after assembly of the electrical circuit, and the variable shield adjustment providing attenuation of the electrical circuit output.

Abstract: A pressure switch is provided for opening and closing an electrical switch based on a pressure set point. The pressure switch includes a housing having walls defining a fluid chamber adapted to receive a fluid. The pressure switch also includes a snap disc having a front surface in pressure communication with the fluid chamber and responsive to switch states between first and second shapes. The pressure switch further includes a circuit board having printed circuitry and first and second electrical terminals. The snap disc has a rear conductive surface that forms a closed circuit between the first and second terminals when in the first shape and forms an open circuit when in the second shape.

Abstract: A heater having a shut off device is provided which prevents false over temperature lockouts. The heater comprises a body having walls defining a volume for holding water, a heating element thermally coupled to the body for heating water within the body, and a temperature sensor for sensing temperature of the material. The heater also has a shut off switch for shutting off electric current in the heater when the sensed temperature of the water exceeds a predetermined maximum temperature limit, and a manually actuated reset input for resetting the shut off switch to allow current to be applied to the heater. The heater further includes a controller coupled to the shut off switch and the reset switch, wherein the controller determines the presence of a false over temperature event and overrides the need to manually actuate the reset input.

Abstract: A motor start circuit for A-C electric motors. A microprocessor-based circuit is used to detect the phase shift that occurs in the motor current as the motor goes from the initial locked-rotor state to the running state. This circuit applies current to a motor `start` winding when the motor is first switched on, but turns off the start winding when the motor achieves sufficient running speed, as indicated by the shift in phase of the current in the motor's `run` winding. For bi-directional motors with two start windings, the microprocessor can apply current to either start winding.