Abstract: There is disclosed a fire alarm system wherein a plurality of fire detectors are connected to each alarm line and a light emission diode is connected in series between an alarm line and an electric source, said light emission diode indicating the actuation of any of the fire detectors, said system being capable of monitoring the alarm lines for breakage or disconnection without interruption of its fire monitoring function. This fire alarm system comprises a pulse oscillator; a switching circuit; a voltage detection circuit; two light emission diodes; a delay circuit; means for forcibly turning on the switching circuit; a capacitor; and a high resistance resistor.

Abstract: A fire detecting system is disclosed, which comprises a sensor for producing an output voltage representing smoke level, heat, etc., and a comparator for producing a fire signal by comparing the output of the sensor or the differential or integral of the sensor output and a reference voltage. The sensor output or the differential or integral thereof is held in a peak hold circuit to be transferred through a switch to a sample-hold circuit for storage there.

Abstract: A novel signal transmission system, having a junction line comprised of a power source line, a grounding line and a signal line is disclosed. Two complementarily operative transistors are connected in series between the power source line and the grounding line. Signals are sent out from the junction point of the two transistors to the signal line. The speed for transmitting the signals is effectively increased due to the quick charge and discharge of the signal line.

Abstract: In the fire alarm system comprising a pair of alarm lines, a plurality of fire detectors connected between said alarm lines and a receiving unit connected at the proximal end of the alarm lines, and generating a fire alarm in response to an alarm signal raised by one or more fire detectors, an improved system in which disconnection of alarm lines and number of fire detectors producing alarm signals can be indicated, is disclosed.

Abstract: In a fire detector that includes a sensor for producing an output voltage corresponding to smoke concentration, temperature, etc., there is provided a charge-and-discharge circuit to be reset by the turning ON of a switching circuit which is made ON at a fixed voltage. The output of the charge-and-discharge circuit and the output of a sensor are applied to the switching circuit to vary the ON period of the switching circuit corresponding to the output voltage of the sensor. Any irregularity in the sensor can be monitored by changes in the ON period.

Abstract: In a smoke detector of the type in which smoke is detected in a detection chamber based upon a variation of an ionization current flowing therein or a variation of light beam passing therethrough, there is provided a reference signal generating section which produces a reference signal having a predetermined characteristic corresponding to typical smoke flowing into the detection chamber when a fire occurs, and a signal comparison section which compares a detection signal detected in the detection chamber with the reference signal, wherein a smoke sensing signal is produced when the detection signal is determined as a signal due to a fire but is not produced when the detection signal is determined as the signal due to the entry of an insect into the detection chamber or due to cigarette's smoke flowing thereinto.

Abstract: When a receiver supplies both an address signal and a test instruction signal to a given terminal unit, a test voltage generator forming a sensor test circuit of this terminal unit supplies a predetermined test voltage to a corresponding sensor. This sensor generates an analog signal obtained by superimposing the test voltage on the normally detected voltage. The analog signal is A/D-converted, and a resultant digital signal is received by the receiver, thereby allowing a test for operating conditions of any sensor at the site of the receiver. The test voltage generator may generate a plurality of stepwise voltage components to readily check operating characteristics (e.g., overload characteristic) of the sensor.

Abstract: A test circuit for fire detection systems and the like is designed for use with detectors which bridge across a pair of lines. The detectors become conductive if a condition such as a fire is detected, or if a predetermined number of test pulses is applied to them. Test pulses are applied across the pair of lines. A relay is connected to one of the lines and, when latched, generates an alarm signal. A resistor is placed in series with the relay so the relay cannot latch even when one of the detectors has become conductive. A first circuit produces a confirmation signal when at least one of the detectors is conductive. This signal is delayed in an RC network. A second circuit shorts the resistor after the delayed confirmation signal is received, so that the relay can latch to generate the alarm signal.

Abstract: A selectively testable fire detector comprises a fire detecting circuit supplied with a first voltage and which detects smoke and/or temperature, a self-holding circuit which is actuated by the output signal of the fire detecting circuit, a counter which counts pulses superimposed on the first voltage and outputs a signal when the counted number reaches a predetermined number assigned thereto, a latch circuit which latches the output signal of the counter and transmits to the fire detecting circuit a signal which actuates the fire detecting circuit, and a reset signal generating circuit which resets the counter and latch circuits by a second voltage which is higher than the first voltage.

Abstract: A circuit for selectively or extractively testing a fire detector among a plurality of fire detectors which are connected between an alarming line extending from the section relay of a receiving unit and a common line is disclosed. An inherent address code is allotted to each fire detector. When an address signal transmitted through the alarming line coincides with the allotted inherent address code, a coincidence signal is produced and in response to said coincidence signal a test voltage is generated for each fire detector.

Abstract: A combination type smoke detector comprising a light scattering smoke detector and an ionization smoke detector in which a labyrinth structure dark chamber for the light scattering smoke detector is made of an electroconductive plastic material and functions as the outer electrode of the ionization smoke detector is disclosed. Members of the ionization smoke detector and the light emitter and the light sensing element for the light scattering smoke detector are arranged so that the light emitted from the light source and reflected by said members and the lamina members does not enter the light-sensing element.

Abstract: By the employment of the heat-sensitive thyristor, the conventional rate-of-rise action fire detector having a diaphragm deformable by thermally expanding air in a restrictively vented air chamber is easily converted to a combination type fire detector with minimal redesigning or additional fabrication and with an efficient mounting of the thyristor on a metal casing defining the air chamber.

Abstract: An optical smoke detector which includes a light source and light sensing element so arranged that the quantity of light detected by the element will be determined by the presence of smoke in the detector, a power source for periodically supplying sets of actuating pulses to the light source, apparatus connected with the light sensing element for detecting light pulses which are synchronized with the actuating pulses and producing an alarm when pulses of a predetermined magnitude are detected.

Abstract: A smoke detector having a housing including openings for admission of smoke, a smoke detecting chamber within said housing with the wall of said chamber formed of spaced overlapping elements which form a serpentine path therebetween, means on one side of said chamber for emitting light into said chamber, a light detector adjoining and shielded from said light source and a conical reflector in said chamber and on a side opposite said light source and detector.

Abstract: The method of manufacturing a cation exchanger which includes chopping up waste tires and then successively heat treating and then sulfonating the resultant product.

Abstract: A gas sensing element which varies its resistivity upon the adsorption of gas and which has a sintered body including an oxyacid salt semiconductor and which may also contain carbon.

Abstract: A fire and smoke damper for installation in a duct which includes a plate rotatably mounted within the duct and having means enclosing the periphery of the plate and biased outwardly to engage the duct wall when the damper is in the closed position.