Abstract: A flat valve device of a smaller size which can complete easy and swift air evacuation, in which the airtightness of a gas-containing structure and the operational safety can be improved, requiring no extra parts. The flat valve device includes a circular frame member 3 to be mounted on the opening of a gas-containing structure 2, a round body member 4 to be removably screwed to the inner peripheral surface 4d of the circular frame member 3, and a valve 6 provided in a valve accommodating space of the round body member 4. The round body member 4 is provided with an outward-facing through hole 4e and an inward-facing through hole 4f, while the valve 6 includes a sealing cover 6a and an energizing member 6b.

Abstract: Fire detection signals are produced with high reliability based upon a quantity smaller than a predetermined quantity from a fire sensing system which detects predetermined standard quantities of combustion products (or physical quantities) such as heat, smoke or light produced by a fire. The system includes a fire sensor connected in parallel with a first semiconductor switching element and a second semiconductor switching element contained in two independent power-supply circuits. The first power-supply circuit contains the first semiconductor switching element which detects a combustion quantity smaller than the standard quantities and which is rendered conductive upon receipt of an early output produced by the fire sensor. The first power supply circuit is connected in parallel with a second power-supply circuit containing the second semi-conductor switching element which detects the standard quantities and which is rendered conductive upon receipt of an alarm output produced by the fire sensor.

Abstract: In an ion type smoke sensor including a smoke sensor having an internal electrode, an intermediate electrode and an external electrode, and a field effect transistor having a control input terminal connected to the intermediate electrode, a first output terminal connected to the internal electrode and a second output terminal connected to the external electrode, an ion type smoke sensor of this invention comprises an oscillator circuit for generating an oscillating output having a predetermined oscillating frequency; a reference level source for intermittently producing an output signal with a predetermined reference level in response to the oscillating output from the oscillator circuit; and a comparing circuit for comparing a sensing output between the first and second output terminals of the field effect transistor with the reference level from the reference level source to produce a fire sensing signal in accordance with the result of the comparison.