Abstract: A transformerless power circuit for heating a filament of a fluorescent display comprises integrated circuit timing means comprising two timers having output terminals for developing alternating output signals of opposite polarity with respect to a d.c. bias-component of each output signal. The circuit also includes external resistor means, condenser means and voltage supply means for controlling the frequency of the timers. The circuit also includes d.c. bias component resistor means coupled to the output terminals for developing biascomponents of the same polarity at the display filament terminals with respect to a common reference potential for connection to a fluorescent display filament.

Abstract: A parameter control system for an oven which may, for example, be a baking oven or a convection oven having the capability of injecting steam into the cooking cavity. The parameter control system precisely controls cooking temperature, cooking time, humidity and air flow in the oven. The parameters can be easily and repeatably set.

Abstract: An air filtration system for removing smoke and grease from cooking exhaust of ducted range hoods is disclosed. In particular, the system includes a coarse filter device fine filter device which substantially remove all of the cooking effluents from the cooking exhaust drawn into the system by a fan powered by a variable speed motor. A sail switch device is connected to the motor and is positioned in the system to determine the flow quantity of the air drawn into the system and to maintain this flow quantity at a substantially constant volume by controlling the speed of the motor device. A maximum speed of the motor is determined by an indicator device signaling an operator to change filters clogged with cooking particles.