Abstract: A method and apparatus in a smoke detector for comparing an analog signal voltage to a digital alarm threshold and for converting a digital sensitivity value to an analog test voltage. The analog signal voltage is converted to a digital value by: a) charging a capacitor at a first linear rate directly proportional to the analog signal voltage, for a predetermined time period; b) discharging the capacitor at a second predetermined linear rate to a predetermined threshold; c) counting during the discharging of the capacitor to establish a digital count representing the signal voltage; and, d) comparing the digital count to a an alarm threshold stored in the detector prior to its installation. The digital sensitivity value is converted to the analog test voltage by: charging the capacitor from the first predetermined voltage, at a predetermined rate, for a time period based on the sensitivity and a calibrated conversion factor. This charges the capacitor to an analog voltage representing the sensitivity.

Abstract: A process and apparatus are provided for calibrating an individual smoke detector prior to installation so its sensitivity can be determined easily throughout its useful life. Representations of detector output signals are stored in the detector prior to installation, preferably at the time of manufacture, and used later for determining the sensitivity of the detector. The signals may represent alarm and clean-ambient conditions, or one of such conditions and the difference between them. During monitoring of the detector, after its installation, a new reading of a corresponding signal under clean-ambient conditions is sampled and the differences before and after installation are compared to determine the sensitivity of the detector when it is monitored. The detector includes electrical contacts from which a representation of detector sensitivity is available for monitoring with an external electrical probe, such as a common voltmeter.

Abstract: A fire detector which combines an NDIR CO.sub.2 gas detector with a photoelectric smoke detector to minimize false alarms by logic means that can be integrated into a single chip that can have an ASIC section and a microprocessor section. The NDIR CO.sub.2 detector can be single or dual channel. The NDIR CO.sub.2 gas detector and the photoelectric smoke detector can be separate or combined in a single device in which they are optically isolated by a light-tight barrier but still use a common light source. Also, the CO.sub.2 and smoke detectors can be combined on a single substrate within a common housing.

Abstract: A multi-signature fire detection method and apparatus, utilizing first and second detectors for detecting first and second fire signatures. The first detector outputs a first signal indicative of the first detected fire signature, and the second detector outputs a second signal indicative of the second detected fire signature. A signal processor is provided for combining the first and second signals using a number of correlations, wherein outputs of the first and second detector means are coupled to the signal processor, and the signal processor compares and combines the first and second signals to a first predetermined reference value, and outputs a fire condition signal if a combination of the first and second signals exceeds the predetermined reference value.

Abstract: A light detection apparatus includes a light detector using a photoelectric converter such as a photodiode. The light detector has a selective viewport that limits the field of view observed by the photoelectric converter. The photoelectric converter generates a current signal based on the light received through the selective viewport. Using current-mode amplification, a current amplifier generates an amplified current signal based on the current signal received from the photoelectric converter. A switch coupled to receive the amplified current signal from the current amplifier, generates an output signal based on the amplified current signal. The switch can be implemented to generate the output signal with predetermined logic levels compatible with a desired logic family.

Abstract: An inexpensive smoke detector having excellent general versatility and reliability allows for an increase in a range of selecting light emitting devices used for such smoke detectors and allows for reductions in the number of processes and adjustment equipment, thereby reducing costs and avoiding human adjustment errors. The smoke detector includes an A/D conversion circuit for measuring an output from a photo transistor which receives a light output of at least a light emitting diode used for smoke detection. A MPU generates a signal for driving the light emitting diode, based on a value measured by the A/D conversion circuit. The smoke detector also includes an EEPROM. A D/A conversion circuit adjusts a light emission quantity of the light emitting diode based on a value read from the EEPROM. The smoke detector further includes a voltage/current conversion circuit.

Abstract: A fire detector capable of readily and accurately adjusting the sensitivity thereof and of not erroneously outputting any fire signal is provided with a first-stage amplifying circuit having an output adjusting variable resistor and a fire discriminating section having a reference voltage adjusting variable resistor. As a result, it is possible to adjust the amplified output to a predetermined value by the switching level of the fire discriminating section to a predetermined value by the reference voltage adjusting variable resistor.

Abstract: In a light scattering smoke sensor of the present invention, a first diaphragm portion is disposed just aheat of a light receiving device, and a second diaphragm portion is disposed ahead of the first diaphragm portion. A gap between the first and second diaphragm portion is a smoke introducing portion which introduces smoke to a smoke detecting space via a gap between labyrinth members and the second diaphragm portion.

Abstract: Apparatus for testing the sensitivity of a smoke detector (12) in-situ, including a head assembly (1) comprising a housing (14) for surrounding a smoke detector in-situ and forming part of a sensing loop (14, 15, 16, 17)through which air carrying an aerosol will circulate, a sensor (25, 26, 27) for sensing the concentration of aerosol in the air circulating in the loop, a fan (20) for causing air to circulate in the loop, an aerosol container (24) for supplying aerosol to the loop and a control unit 2 for controlling the concentration of aerosol in the air circulating in the loop by controlling the fan (20) and the aerosol container (24) in response to the output of the sensor.

Abstract: A fire sensor according to the present invention includes a sensor base, a sensor body and an address unit. The sensor base is mounted and fixed on a predetermined position, for example, a ceiling. The sensor body includes a plurality of pins for electrically connecting the sensor body with the sensor base, and a first fitting member for electrically and mechanically connecting the sensor body with the sensor base. The plurality of pins are formed on a surface of the sensor body connectable to the sensor base and circumferentially arranged on a circle with a predetermined radius. The sensor base has a second fitting member which is electrically and mechanically fitted to the first fitting member.

Abstract: An allergen particle detecting apparatus has a passageway through which environmental air is directed. A light beam is directed across the passageway so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the passageway blocks any non-scattered portion of the beam while transmitting any scattered portions of the beam along a light path in the apparatus. Any light scattered by allergen size particles will be traveling in a predetermined angular range, and a pinhole device is positioned in the light path so as to transmit only light traveling in that angular range. Light transmitted through the pinhole device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level.

Abstract: A light scattering type smoke detector arranged such that even if the range in which light from an LED is emitted has a dispersion, a labyrinth member 90 in the light emitting range has no edge or only a predetermined labyrinth member exist therein. The labyrinth member 90 is preferably formed by a single plate larger than the other labyrinth members 9. The edges of the labyrinth members 9 are preferably formed to a curved surface or chamfered, and the dispersion of the 0 point of a detection output is reduced and the level of the 0 point of the detection signal is lowered to thereby accurately detect light scattered by smoke.

Abstract: An ionization chamber for use in a smoke detector includes first and second outer electrodes and a non-reflective center electrode. The non-reflective center electrode can be formed as a metal electrode having a non-reflective coating or as a non-reflective, conductive plastic elements. The ionization chamber can be incorporated into combination smoke detector which includes a photoelectric sensor. A non-reflective center electrode, associated with the ion-type sensor is symmetrically located in the detector and displaced from the photoelectric sensor.

Abstract: A photoelectric type fire detector is capable of accurately adjusting sensitivity using a scattering and translucent plate and exhibits excellent reliability.

Abstract: A projected beam-type smoke detector of the type in which a light emitter having a light emitting element is separately mounted from a light receiver having a light pickup element in order to detect a fire by an attenuation in the level of light which the light receiver receives from the light emitter, attenuation being due to the presence of smoke between the light emitter and the light receiver. The detector, comprising the light receiver, a cover status sensor for sensing the closing or opening state of a cover that is closed or opened to allow adjustments such as optical axis adjustment, sensitivity setting for light input and the like, and a control block for controlling each section of the light receiver. The control block sets the adjustment mode to each section of the light receiver when the control block receives a cover open-state signal indicative of the opening of the cover from the cover status sensor. The adjustment mode is automatically set to each section of the light receiver.

Abstract: A self-testable photoelectric smoke detector incorporates a housing which defines an internal smoke chamber. The housing carries a laser diode and a radiation sensor along with a supplemental source of test radiant energy. When a test is initiated, the operational characteristics of the laser diode are monitored simultaneously with energizing the source of test radiant energy. Signals from a scattered radiant energy sensor are evaluated via control circuitry, along with signals indicative of performance of the laser diode to determine whether or not the laser diode as well as the radiation sensor are functioning properly.

Abstract: A first dust recovering part is disposed upstream in an air inlet passage from a fire detecting part. The air flow is deflected in the first dust recovering part so as to cause the dust to drop to separate from the air and to be recovered in a recovery area of the first recovering part. Farther downstream from the first dust recovering part, a second dust recovering part is arranged having a filter for recovering dust in the air which has passed through the first dust recovering part. Thus, clogging of the filter is avoided and erroneous operations caused by dust are more reliably reduced. As a result, the reliability of the fire detecting apparatus is improved.

Abstract: A smoke detecting apparatus for a fire alarm has a smoke chamber into which smoke to be detected is introduced, a light emitting lamp disposed in the smoke chamber, a light receiving element disposed in the smoke chamber so as to receive the light emitted from the light emitting lamp, an amplification device for amplifying an output signal from the light receiving element, a detection device for detecting the density of the smoke on the basis of an output signal from the amplification device, a comparison device for comparing the value of the output signal from the amplification device with a fixed value, an abnormality output device for outputting an abnormality indication when the value of the output signal from the amplification device is judged to be smaller than the fixed value by the comparison device, an augmentation command switch for commanding augmentation of the value of the output signal from the amplification device, and an augmentation device for augmenting, in accordance with a command from the

Abstract: A wall-mounted stand-alone smoke detector has an elongated housing. The housing has two ends. One end forms a base. The other end houses a sensor head remote from the base. A rigid member supports the sensor and connects the sensor to the base. The sensor head has a smoke sensor, a signal conditioner and a preamplifier for respectively detecting, conditioning, amplifying and providing signals from the sensor to a signal processor in the base. A positioning probe is attached to the sensor head end of the housing for positioning the sensor spaced from a ceiling of a room. The end housing the sensor may be angled for spacing the sensor from a wall on which the detector is mounted. All mounting, display control interaction and routine maintenance can be performed within easy reach, without climbing. The base has a power supply. A signal processor in the base is connected to the sensor head. Circuitry analyzes and processes signals, recognizing an alarm state and activating audible and visual alarms.

Abstract: A light scattering type smoke sensor of the present invention has a plurality of labyrinth members for facilitating an inflow of smoke entering from the outside, and for cutting off light entering from the outside; a plurality of smoke inlets each of which is formed by a space between paired ones of the labyrinth members being adjacent to each other; a smoke detecting chamber which is formed in a center portion by the labyrinth members; light emitting device for radiating light toward the smoke detecting chamber; and light receiving device for detecting light which is scattered by the smoke in the smoke detecting chamber, the light receiving device having an optical axis which intersects in the smoke detecting chamber an optical axis of the light emitting device at a scattering angle in the range of 60.degree. to 80.degree.

Abstract: A smoke detector that operates on the principle of scattered light is disclosed that has the capability of an operating sensitivity that is tens of times greater than that of smoke detectors presently available. Plural light sources are used, their light rays directed radially toward the center of a cylindrical detector chamber having a mirrored wall that reflects light back toward the chamber's center, thereby to brightly illuminate a central detection zone. Scattered light from smoke in this zone is detectable by a photocell at right angles to the converging multiple light rays. To obtain highly improved stability of the light output that enables ultra-high sensitivity, the light sources are light-emitting diodes in series connection and they are driven by a very stable constant voltage source that also powers the photocell detector. This system gains impressive sensitivity while reducing nuisance alarms that have been a common problem regarding efforts to increase smoke detector sensitivity.

Abstract: A long life, surface mountable ambient condition detector includes a non-replaceable battery for the purpose of providing power to the detector. The detector includes an activation switch mechanism having a one-time, or single use turn-on characteristic. The activation switch mechanism switches the battery once from a non-conducting state to a state of electrical conduction with a control unit of the detector. The switch mechanism may include a frangible member for switching the battery from the non-conducting state to the electrical conducting state. Until the detector has been energized, the frangible member blocks mounting of the detector on the surface.

Abstract: A fire alarm system comprises a first light emitting device (11), a first polarizing filter (31), a first light receiving device (21), a second light emitting device (12), a second polarizing filter (32), and a second light receiving device (22). With the above arrangement, the amount of the parallel polarized component to the scattering plane as well as the amount of the perpendicular polarized component to the scattering plane is detected. The ratio between these amounts of light has a correlation with the type of smoke. A calculation section (4) calculates this ratio from the outputs of the light receiving devices (21, 22). A decision section (6) compares the above-described ratio with a reference value which has been preset according to the type of smoke to be detected, whereby the judgement of whether there is a fire or not is performed depending on the type of smoke. Thus, the detection of a fire can be performed from the light scattered by smoke taking into account the type of smoke.

Abstract: A photoelectric type fire detector includes self-testing capabilities. An upper level threshold limit and a lower level threshold define a predetermined range for output levels of an amplifier connected to an output of a light receiving element. In a self-test mode, a gain set in the amplifier is increased automatically. The number of times in which the amplifier output level deviates from the predetermined range is counted. If the deviation count exceeds a predetermined count threshold, it is determined that the photoelectric type fire detector is abnormal.

Abstract: An apparatus for detecting fire including a light source for generating light, a light sensor for receiving light from the light source and providing an analog signal representing the intensity of the received light, and a clear plastic light guide for transmitting the light from the light source to the sensor. The light guide include notches for allowing smoke to enter the notches. Smoke entering the notches decreases the intensity of the light passing therethrough. A calibration sensor is included. The sensitivity of the fire detector is increased by a lens assembly which collimates the light generated by the light source. The color of smoke entering the light guide may be determined by generating colored light. Temperature, humidity and carbon monoxide levels are also detected and the information is integrated with the smoke detection data to provide a reliable fire detector.

Abstract: A smoke detector is provided with testing apparatus for determining if its sensitivity is within a predetermined acceptable range. The testing apparatus stores in the detector a range representing acceptable sensitivities. When a test is initiated the resulting test output is compared to the sensitivity range, or its representation, and a warning signal is provided when the output is not acceptable. According to one feature, the stored representations of the acceptable range include a maximum acceptable value and a minimum acceptable value, and the warning signal indicates when the output is above the maximum or below the minimum. According to other features, the output signal is periodic at one frequency when above the maximum and at another frequency when below the minimum. The test is initiated by a magnetic reed switch and the results are immediately apparent.

Abstract: A smoke detecting system monitors smoke from different monitored areas. A main system fan is energized to draw air from all the monitored areas through a smoke detecting unit via individual pipes and via a location unit. When smoke is detected, a control unit produces an indication. In addition, it energizes a sequencing unit which switches off the main fan and then sequentially and individually energizes small fans, each of which draws air through a respective one of the individual pipes and feeds it through the smoke detection unit. When the small fan corresponding to the pipe connected to the particular one of the monitored areas from where the smoke originates is energized, there will be an increase in the output of the smoke detector. This is detected by the control unit which causes the sequencing unit to identify this monitored area on an indicator.

Abstract: A self-contained smoke detector system has internal self-diagnostic capabilities and accepts a replacement smoke intake canopy (14) without a need for recalibration. The system includes a microprocessor-based self-diagnostic circuit (200) that periodically checks sensitivity of the optical sensor electronics (24, 28) to smoke obscuration level. By setting tolerance limits on the amount of change in voltage measured in clean air, the system can provide an indication of when it has become either under-sensitive or over-sensitive to the ambient smoke obscuration level. An algorithm implemented in software stored in system memory (204) determines whether and provides an indication that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits. The replaceable canopy is specially designed with multiple pegs (80) having multi-faceted surfaces (110, 112, 114).

Abstract: A process and apparatus are provided for calibrating an individual smoke detector prior to installation so its sensitivity can be determined easily throughout its useful life. Representations of detector output signals are stored in the detector prior to installation, preferably at the time of manufacture, and used later for determining the sensitivity of the detector. The signals may represent alarm and clean-ambient conditions, or one of such conditions and the difference between them. During monitoring of the detector, after its installation, a new reading of a corresponding signal under clean-ambient conditions is sampled and the differences before and after installation are compared to determine the sensitivity of the detector when it is monitored. The detector includes electrical contacts from which a representation of detector sensitivity is available for monitoring with an external electrical probe, such as a common voltmeter.

Abstract: A smoke type fire detector accurately detects a smoke density even when an internal temperature thereof changes. An internal temperature detecting unit detects an ambient temperature at a light emitting element and a light receiving element. A correction coefficient having a value associated with the ambient temperature detected by the temperature detecting unit is used to correct an output level of the light receiving element.

Abstract: The present invention provides a method for detecting whether an alarm circuit is operating outside its sensitivity range, the alarm circuit having a background signal and a preset alarm threshold signal. The method involves: a) multiplying the background signal by a first gain factor to produce a first test signal; b) comparing the first test signal against an alarm threshold signal; c) multiplying the background signal by a second gain factor less than the first gain factor to produce a second test signal; and d) comparing the second test signal against the alarm threshold signal. The alarm circuit is operating outside its sensitivity range when the first test signal is less than the alarm threshold signal or the second test signal is greater than the alarm threshold signal.

Abstract: A device (7) for testing the operation of smoke detectors (3) has a housing (1) which is open at one end and can be placed over the smoke detector (3). A test light source (5) in the housing provides light pulses which radiate into the inside of the smoke detector (3) under test. The test device also has a test light detector (4) that receives light coming from the smoke-indicating light source (15) of the smoke detector (3) and controls the test light source (5) in relation to the received light. The light pulse of the test light source (5) is received by the smoke-indicating light detector (14) of the smoke detector (3). By checking if the smoke detector (3) goes into the alarm state, it can be ascertained whether it is in an operational condition.

Abstract: A mobile fire detecting system for detecting fire conditions at the incipient stage before visible smoke has been released having an air sampling fire detector mounted to a cart supported by wheels. A tubular network in communication with the air sampling detector has a manifold enclosed by a box with four sensing hoses releaseably connected to the lateral outlets of the manifold and a telelscoping mast supporting the manifold to position it at selectable heights. Four sampling heads are connected to the other ends of the sensing hoses and are peripherally spaced equally so that the maximum area is sampled for air to detect fire conditions.

Abstract: A separate type photoelectric smoke sensor having a light emitting section for emitting a light beam to a reflecting plate disposed at a certain distance from the light emitting section, a light receiving section for receiving reflected light from the reflecting plate, and a judgement section for outputting a sense signal if a received light output from the light receiving section is smaller than a threshold value previously set.

Abstract: For testing or/and adjusting a scattered-light smoke detector as to sensitivity to smoke, a transparent body with included scattering centers is introduced into the measurement volume of the detector. Aluminum oxide powder particles can serve as scattering centers. The distribution of light scattering centers is preferably uniform, and their concentration chosen to simulate a smoke density corresponding to the alarm threshold of the smoke detector. Thus, scattered-light smoke detectors are readily calibrated to a desired output signal as a function of smoke density. With a different density of scattering centers, the technique can be used for testing scattered-light smoke detectors in the field. If the scattering centers are distributed outside a measurement volume of an uncontaminated detector, the technique can be used for testing as to contamination.

Abstract: A photoelectric sensor of the present invention includes a light emitting device and a light receiving device for detecting scattered light due to smoke, a light emitting confirming device which lights up when a quantity of light received by the light receiving device is greater than or equal to a threshold and a test light emitting device for emitting light to the light receiving device during the test, wherein a blinking of the light emitting confirming device is started at a time of a test start, and a quantity of light received by the light receiving device is increased in steps so that the blinking is stopped when the quantity is greater than or equal to the threshold. Accordingly, the sensitivity test can be performed by visually counting the number of blinkings of the light emitting device.

Abstract: A photoelectric type fire detector has: a detector body; a printed circuit board disposed on the upper side of the detector body; conductive connecting members provided on the lower side of the detector body; terminal screws for simultaneously fixing the printed circuit board and the conductive connecting members to the detector body; an optic base directly placed on the upper side of the printed circuit board and having a labyrinth formed on the upper side thereof; hooks for fixing the optic base to the upper side of the printed circuit board; a light-emitting element and a light-receiving element arranged in a pair for detecting smoke; a bug screen provided on the outer periphery of the labyrinth of the optic base; an optic base cover covering the upper side of the optic base; and a protective cover covering the printed circuit board, the optic base, the bug screen and the optic base cover.

Abstract: A light emitting device for projecting a light beam onto a monitor area, and a light receiving device, arranged so that a light beam is not directly received by the device, for receiving diffused light caused as a result of fine particles, such as dust, or smoke caused by a fire, entering the monitor area, are provided. Also, an amplifying device for amplifying an output from the light receiving device, and a counting device for counting the output from the amplifying device in units of time are provided. In addition, a computing device for computing an average value or an integrated value of the output from the amplifying device in units of time, and a determining device for determining the level of contamination of the monitor area on the basis of the count value of the counting device and for determining the level of the fire on the basis of the average value or the integrated value computed by the computing device, are provided.

Abstract: A photoelectric smoke detector has test circuitry for testing the detector by increasing the sensitivity thereof. The sensitivity is increased by either altering a bias condition of a photosensor or by altering a gain parameter of the detector. The detector returns to a quiescent state when the sensor returns to its original bias condition or when the gain parameter returns to its quiescent value.

Abstract: A smoke detecting apparatus for a fire alarm has: a smoke chamber into which smoke to be detected is introduced, a light emitting lamp disposed in the smoke chamber, a light receiving element disposed in the smoke chamber so as to receive the light emitted from the light emitting lamp, an A/D converting circuit for converting the output signal from the light receiving element into a digital signal, a memory for storing data therein, a computing device for storing in said memory, as first calibration data, the output data from the A/D converting circuit when the smoke chamber is filled with a first reference gas, storing in said memory, as second calibration data, the-output data from the A/D converting circuit when the smoke chamber is filled with a second reference gas, and computing a proper smoke density corresponding to the output data from the A/D converting circuit on the basis of the first and second calibration data and the output data from the A/D converter circuit, and a display device for displayin

Abstract: Optical smoke detectors such as extinction smoke detectors and scattered-light smoke detectors include a radiation source, a radiation detector or receiver, and a measurement volume which is in communication with ambient atmosphere and which is traversed by a light path from the radiation source to the radiation receiver. For compactness and simplicity, such an optical smoke detector is provided with a planar-optical element in the optical path. Suitable as planar-optical elements are diffractive elements, e.g., holographic-optical elements (HOE), and micro-Fresnel elements (MFE), e.g., micro-Fresnel reflectors (MFR).

Abstract: A smoke detector in which a plurality of labyrinth members are disposed on an upper wall in a standing position. In an area surrounded by the labyrinth members, a smoke detecting chamber is formed. A light emitting device and a light detecting device are disposed in such a manner that their optical axes intersect each other at the center of the smoke detecting chamber. In order for the visual field of the light detecting device with respect to the smoke detecting chamber to be restricted to the front area thereof, the labyrinth member which cross the optical axis of the light emitting device is formed so as to be longer than the other labyrinth members, and a gap is formed between the front end of the long labyrinth member and a light shielding plate for preventing the light emitted by the light emitting device from directly reaching the light detecting device.

Abstract: A silencable photoelectric-type detector includes a source of radiant energy and a detector. A generator circuit provides a sequence of pulses to energize the source. A biasing circuit biases the detector. The detector can be temporarily silenced, when in alarm, by reducing the energy level of the pulses or altering the bias point of the detector for a period of time. The period of time can be established by an RC circuit. The effect of the energy level reduction or the bias point alteration is to reduce the sensitivity level of the detector temporarily.

Abstract: An obscuration type optical smoke monitor is provided for use particularly in dusty and dirty environments. The smoke monitor comprises a housing enclosing a smoke monitoring chamber; two access ports located opposite each other on the housing; a shunt air flow path located between said two access ports; means to conduct air from said access ports through an optical chamber; a light emitting diode at the first end of said optical chamber, which light emitting diode produces a light beam axially through the center of said optical chamber; a photo transistor at the second end of said optical chamber to receive the light bean and issue an electrical signal proportional to the received light intensity; and an electronic module which provides variable electronic output, generating an analog output essentially proportional of the optical obscuration caused by the smoke.

Abstract: A integrated IR detector for detecting both motion and fire/smoke includes in one embodiment a single source of IR radiation and separate IR sensors for sensing motion and smoke. The separate sensors are coupled by their outputs to separate amplifier circuits and provide separate outputs indicating motion (intrusion) detection and smoke detection. The entire arrangement of IR source and dual sensors are mounted in a single housing and powered by a common power supply. In a second embodiment, a single passive IR motion detector having a pair of phase opposed series connected sensors is coupled to a circuit for detecting motion (intrusion) while one of the pair of sensors is coupled to a circuit for sensing changes in ambient temperature. The circuit for detecting ambient temperature changes includes logic analysis and time constant filtering to produce an alarm signal only when ambient temperature changes exceed a preset threshold rate of degrees per second.

Abstract: An improved smoke detector in combination with a fan assembly for reducing the likelihood of smoke detector activation by ambient smoke, has a fan with a timer controlling the fan's motor to automatically shut off the fan either when the time has expired or if the timer fails.

Abstract: A smoke detector includes a dark chamber surrounded by a peripheral wall structure having a plurality of nested vanes. The second element of each vane is shorter than the first, and intersects the first element intermediate its ends at an acute angle. Adjacent vanes define a tortuous path that requires a minimum of three, and in most cases four, reflections for light to reach the inside of the chamber. Adjacent vanes define twisted channels leading from outside the chamber into the chamber for blocking light without substantially restricting the flow of air. The channels each include an outer section that extends in a direction toward the center of said chamber to define a channel entrance that admits airborne smoke with approximately equal resistance from opposite directions. The channels also define second and third sections that bend inwardly from the entrance toward said chamber, first in one direction and then sharply in another direction.

Abstract: A pollution monitoring device including a fluid sampling chamber (21), a collimated light source (14, 15) directing a light beam (10, 11) into the chamber, a port (23) for introducing sample fluid into the chamber exposed to the light beam, a light detector cell (16) separated or shaded from the light beam and focussing apparatus (17) for directing scattered light produced by the presence of suspended particles and molecules in the chamber towards the detector. The source may be two lasers with co-linear beams or an LED. There is also disclosed a sample area of small diameter in which a light beam traverses the area across the flow path of a sample fluid and a projector projecting scattered light from particles into a light receiving zone of notional triangular shape having an included angle of less than 60.degree., to enable discrimination of particle size discrimination.

Abstract: In a scattered-light smoke detector, for preventing false alarms due to extraneous matter in a measurement chamber (1), a radiation source (2) and two radiation detectors (7, 8) are included. An evaluation circuit is provided for comparing the two detector signals, and an alarm signal is triggered if at least one of the detector signals exceeds a predetermined threshold, and if the two detector signals are at least approximately equal. In another embodiment, a scattered-light smoke detector includes two radiation sources (2, 22), a radiation detector (7), and circuitry for alternatively activating one (2) or the other (22) radiation source. For comparison, corresponding detector signals are stored in sample-and-hold circuits, and an alarm signal can be triggered depending on the same tests. Furthermore, in both cases, a trouble signal can be produced if the two signals are significantly different.

Abstract: A smoke detecting apparatus includes a lamp, a light receiving element for receiving light from the lamp, and a smoke detecting circuit for detecting the smoke density in accordance with the signal outputted from the light receiving element. The apparatus further includes a light emission failure detector and counter for detecting a light emission failure in which the lamp fails to emit light in response to a light emission instruction from the smoke detecting and counting light emission failures, and a memory for storing the number of light emission failures. The apparatus may further include a warning unit which, when the number of failures becomes a predetermined value or more, warns that the lamp will soon be exhausted. Thus, the unit enables a maintenance person to replace the lamp without fail before it is exhausted.