Gas, fire and earthquake detector

Abstract

A safety system for a building has an earthquake detector circuit for detecting ground accelerations exceeding a threshold acceleration/frequency curve dividing safe and hazardous ground accelerations throughout a predetermined frequency range. The earthquake detector includes an accelerometer for measuring linear acceleration along an axis, and for generating an acceleration signal indicative of a magnitude of the measured acceleration. A filter circuit produces a filtered acceleration signal from the acceleration signal. The gain/frequency characteristic of the filter circuit is a reflection of the threshold acceleration/frequency curve, such that ground accelerations falling on the threshold acceleration/frequency curve yield a filtered acceleration signal having a substantially constant value throughout the frequency range. Finally, a threshold circuit compares the filtered acceleration signal to a predetermined threshold voltage, and produces an earthquake detected signal indicative of the comparison result. The safety system can also include a gas detector circuit capable of detecting a gas in air, and generating a gas detected signal in response to detection of the gas. A smoke detector circuit can also be provided for generating a smoke detected signal. A main unit including a microprocessor is responsive to the earthquake detected signal, the gas detected signal and the smoke detected signal, and generates a first control signal in response to any of the earthquake detected signal, the gas detected signal and the smoke detected signal. A valve controller closes a gas valve to shut off a supply of gas in response to the first control signal.

Dependencies are inferred from the claim text.