Abstract: A vacuum cleaner includes an agitator brush which only becomes operational when a carpeted floor is being cleaned. In order to avoid erroneous activation of a dust indicator lamp when individual strands of carpet pile are pulled onto the cleaner, a surface discrimination device lowers the sensitivity of a dust sensor circuit, which drives the lamp, when shag or high pile carpet is encountered so as to prevent erroneous signaling of the presence of dust.

Abstract: A method for the determination of smoke concentration is disclosed which comprises heating a sample smoke containing a SOF (soluble organic fraction) component and a dry soot component to a temperature not lower than the boiling point of the SOF component and not higher than the flash point of the dry soot component during the presence of the action of an oxidation catalyst thereby allowing the dry soot component in the waste smoke to be determined by measurement with a smoke tester in a state not affected by the SOF component.

Abstract: A gas detector system for detecting gases such as CO.sub.2. Sample air is passed through a critically sized sealed sample chamber in a sample cell. Infrared waves are generated in an insulated heater assembly, and radiate through windows of the sealed sample chamber concurrent with the sample air. The strength and magnitude of the infrared waves is attenuated by the level of gas, such as CO.sub.2, present in the sample air passing through the critically sized sealed sample chamber, and is sensed by a thermopile detector, including a filter for a specific frequency of infrared energy. Electronic circuitry processes the thermopile signal and measures other parameters of the gas detector to provide a signal indicative of the percentage of gas concentration in the air. Extensive use of insulation about and around the thermopile detector electronic circuitry and other components of the detector maximize stability and reliability.

Abstract: The present invention relates to an apparatus which can be inserted between the stack and a transceiver of a transmissometer to provide zero and span measurements using the primary light source from the transceiver. The apparatus includes a calibration device mounted between the transceiver and one side of the stack and within the path of the light beam. A zero reflector is mounted within the calibration device for movement back and forth between an inactive position and an active position within the path of the light beam to reflect the same amount of light back into the transceiver as the retro-reflector would across the stack when the stack is clear of smoke. In addition, means is connected to the zero reflector for accomplishing this movement. A span filter is also provided within the calibration device which is movable between an active position in the light beam path to provide an upscale reference calibration check.

Abstract: An allergen detector and allergen detection method for sampling the environment where the detector is located and providing an alarm indication when allergen particulates exceed a predetermined level. The invention comprises a housing having a passageway formed therethrough with a fan disposed in the passageway that is responsive to a flow control signal for creating air flow in a first direction through the passageway. At least one filter is disposed in the passageway for removing particulates larger than allergen particulates in air flowing through the passageway in the first direction. An allergen particulate detector is disposed in the passageway downstream of the filter, with respect to air flow in the first direction, for detecting allergen particulates in the air flowing through the passageway and for providing a corresponding detection signal.

Abstract: Method and apparatus for sampling the gaseous medium of a zone or area to determine the concentration, or changes in concentration, of submicron particles suspended in the gaseous medium of that area or zone using an elongated cloud chamber. A light source and a phototransistor are disposed in the cloud chamber and spaced apart so as to be electronically responsive to varying levels of light. A microprocessor is connected to a programmable memory EPROM and has pre-programmed data instructions on particle concentration levels. The EPROM sequences the microprocessor to operate the valves that sequentially sample the gaseous medium in the cloud chamber, and opens the exhaust valve in the cloud chamber to create a condition of reduced gas pressure therein. The sample of gaseous medium containing submicron particles then precipitates or condenses a portion of the cloud in the chamber in proportion to the concentration of the particles.

Abstract: An improved transmissometer and optical assembly therefor contains a solid state light source preferably a light emitting diode. The ligh source emits a low level light beam that is split, part of which is passed through a gaseous sample then directed to a detector while the otehr part is directed to a second detector. Electronic components are provided to use signals from the detectors to control the light source and determine opacity of the sample.

Abstract: In an air contamination level detector for detecting the degree of contamination of the intake air to an internal combustion engine, a laser beam is directed through the intake air stream and light scattered from particles in the intake air stream are detected by a photodetector to generate a pulse for each particle. Pulses over a given size are used to enable an AND gate to pass high frequency pulses to a counter, which is periodically recycled. The count accumulated in the counter represents the duty cycle of the pulses and the dirtiness of the intake air. When the count in the counter reaches a preselected level, it causes a warning light to be energized to indicate that the intake air has a exceeded a tolerance level.

Abstract: A photographic method of collecting and reducing photographic film density data for monitoring air quality is disclosed in which photographic film is first calibrated using calibration scales of known reflectance and the measured radiance of one calibration scale step to relate the photographic film density to the known radiance. Measurement of a target's radiance and sight path radiance is made via target photographic image density analysis and mathematical expressions which convert density information into radiance and/or atmospheric transmittance data using expressions developed from the calibration scale data.

Abstract: A hood assembly for opacity monitoring equipment including an opacity monitor fixedly secured to an outside surface of a smokestack or chimney includes a hood for protectably covering the opacity monitor and associated guide. The guide is connectable to the monitor in a stationary relationship therewith and cooperates with the hood for guiding bodily displacement of the hood relative to the monitor along a substantially vertical path between a lowered condition at which the monitor is substantially covered by the hood and an elevated condition at which the monitor is accessible.

Abstract: A station for locating through laser rays an object likely to diffuse back a part of the incident laser ray, wherein the optical emitter and receiver devices consist of one single device comprising, in the direction of emission, a device for separating the emitted and retrodiffused rays, an optical device converting the emitted parallel beam of small diameter into a divergent beam and a telescope adapted to collimate the divergent beam received from the optical device into a parallel beam of larger diameter, the retrodiffused beam travelling that path in the direction reverse from the emitted beam, the invention being usable for detecting in particular forest fire smokes.

Abstract: In a combined obscuration and scattered-light smoke detector, light from a light source in a smoke chamber is reflected from an image-forming optical component onto a first light sensor which senses a reduced electrical signal in the presence of smoke while a second sensor, viewing light from the light source at an angle, senses an increased electrical signal in the presence of smoke. The output of each receptor is subjected to a band pass filter, an amplifier and a comparator; the resultant signals insure early and reliable activation of an alarm when even a low level of smoke is present in the smoke detector. A second light source having a wavelength different from that of the first light source provides, in the obscuration mode, added sensitivity to smoke.

Abstract: To improve the accuracy and reduce the sensitivity of interference absorptions in a method for determining the concentration of formaldehyde in a medium by an absorption measurement in the range of at least one characteristic absorption band of the formaldehyde and, in the appropriate instance, subtraction of an interference absorption which is determined by at least one absorption measurement in a wavelength range outside of the characteristic absorption band of the formaldehyde, it is proposed that a discharge be maintained at a current strength of several milliamperes in a hollow-cathode lamp filled with molecular nitrogen at a pressure of less than 2 millibar to generate the radiation for the absorption measurement, that the absorption measurement be performed on at least two different characteristic absorption bands of the formaldehyde with absorption coefficients at a previously known ratio to one another which lie in the range of emissions of the gas discharge in the hollow-cathode lamp, that the ratio

Abstract: In an optical media monitoring device that detects presence of light-interrupting media between a photoemitter component and a photoreceptor component provided to operate in cooperation with each other, the photoemitter component is driven at a variable level of light emission, and a comparator compares the output of the photoreceptor component with a reference signal which is also variable. The driving means is controlled to cause the photoemitter component to emit a level of light lower than normally used for media detection. Dust degradation of the sensor is determined by checking, in a state of no media present and the reduced light emission of the photoemitter component, whether the output of the photoreceptor component is greater than the reference signal level.

Abstract: Concentration of a smoke emanating from a combustion engine is determined by projecting beams of light on the flow of smoke in directions traversing the flow of smoke, detecting intensities of beams of light which have traversed the flow of smoke with a light receiving device and calculating a cross-sectional image of the flow of smoke based on detection signals issued by the light receiving device.

Abstract: A pulsed illuminator projector for reducing the reverberation levels of rected ligh by illuminating a lamp that is pulsed on and off at a specified rate and for a specified time duration. The critical factor is controlling the amount of time the light is on versus amount of time it is off, and the frequency at which the lamp is pulsed on. The pulsed illumination projector device reduces the amount of backscatter from particulate matter such as water, zooplankton, dust, fog and the like which causes a significant amount of light to reflect back toward the source thereby reducing visibility. Backscatter is reduced through the reduction of direct incident light. As the backscatter is reduced, the distance which objects can be detected is increased. Illumination is controlled directly by pulse length and repetition rate. The device is completely portable and can be hand held item as well as mounted on a vehicle and operable in gaseous or liquid atmospheres.

Abstract: In a light-transmission type smoke detector, a smoke chamber is composed of a disc-like block of a non-conductive material one side of which has a spiral groove and is coated with a conductive bright metal film and a casing mounted on the block, said casing having a plurality of labyrinth structure smoke entrances. An electric circuit system is placed on the other side of the disc-like block and is covered by a shield sheet. The shield sheet and the coating metal film are electrically connected to shield the electric circuit system.

Abstract: An apparatus and method for determining the extinction of laser light through a fluid is disclosed. The fluid is passed in a conduit having a light transmissive window. A laser beam having intensity I.sub.1 is passed through the window into the fluid. A prong shaped probe having first and second probe sections is disposed in the fluid flow. The first probe section includes a beamsplitter at a distance d.sub.1 from the window for redirecting a portion of the beam onto a first photodiode array, to determine the beam intensity I.sub.2. The remaining portion of the beam tranverses a distance d.sub.2 and is directed through a prism onto a second photodiode array to determine its intensity I.sub.3. Based on the intensities I.sub.1, I.sub.2 and I.sub.3 and given d.sub.1 and d.sub.2, the extinction values E.sub.1 and E.sub.2 may be calculated. Fluid optical density may then be determined as a function of the extinction.

Abstract: In a vacuum cleaner for industry and household in which the speed control for the blower motor for the vacuum cleaner is effected by evaluating the dust concentration given at any time in the suction line by opto-electrical means (light transmitters, light receivers) it is proposed to use the signal pulses, which are derived from the light receivers depending on the measured dust particles, for controlling an additional light transmitter (luminous diode) which directly coacts with a light-sensitive resistor which is at the same time part of the control resistance of a triac connected in the motor circuit of the blower motor. Preferably, the optoelectrical dust concentration measuring arrangement may comprise a plurality of light transmitters and light receivers and may be arranged directly adjacent to the air intake opening of a vacuum cleaner housing.

Abstract: An instrument for viewing the vent of a chimney while the chimney is working that includes a quartz rod that is mounted in the chimney above the flue entrance thereto. The rod is adapted to transmit light travelling down the chimney to a viewing station outside the chimney wall to provide valuable visual information concerning the condition of the chimney and the burning efficiency of the fire.

Abstract: Smoke density measuring apparatus comprising a duct (1) through which the smoke passes, a light source (4) and a photodetector (6) located on opposite sides of the duct adjacent openings (2,3) in the side walls of the duct so that the source (4) directs a beam of light across the duct through the openings to the photodetector (6), a gas supply (10) associated with the openings (2,3) in the side walls of the duct so that gas flows through each opening into the duct, gas flow control valve (13) for varying the rate of flow of gas through said openings, sensor (17) for monitoring the rate of flow of smoke through the duct, and a control circuit (FIG. 4) for controlling the gas flow control valve (13) in a manner dependent on operation of the sensor (17) so that the rate of flow of gas through the openings is reduced when the rate of flow of smoke falls below a predetermined value. The control circuit (FIG.

Abstract: A transmissometer includes electronic shutters for interrupting the transmitted and reference light beams at selected locations and at selected time intervals for establishing the various modes of operation of the transmissometer. The electronic shutters take the form of liquid crystal displays that are selectively energizable to either a clear or an opaque condition. The transmissometer also includes an electronic stepwise light attenuator located in the path of the light beams. The attenuator includes a body and multiple liquid crystal display segments uniformly distributed throughout the body, with the segments being independently energizable to provide stepwise opacity.

Abstract: A system for detection of smoke by measuring changes in the contrast of a multi-contrast target disposed remotely from a photoelectric sensor. The obscuration of the detection path causes a reduction in the contrast of the sensed target, and a change of predetermined magnitude is employed to trigger an alarm. The target has one or more relatively darker and one or more relatively lighter areas which are viewed by the sensor. The sensor can be composed of a plurality of photosensors each viewing a respective area of the target. Or, the sensor can be a single scanning sensor such as a video camera. Only a single line or segment of a line of the video frame pattern need be employed to monitor the target. The video camera can be employed on a shared basis for providing smoke monitoring and detection, together with other functions, such as intrusion detection, access control, or visual surveillance of an area.

Abstract: A gas measuring device has a source capable of emitting a beam of radiation aligned to impinge a detector. A housing means encloses the beam. The housing means has a plurality of apertures permitting the gas to enter the housing means, to intercept the beam, and to exit from the housing means. The device further comprises means to control the amount of thermal radiation reaching the detector.

Abstract: Vacuum cleaner for use in industry and household comprising a housing and an electric motor driving the blower generating the working vacuum, and optional maneuvering means for moving a suction nozzle over the material to be cleaned. There is provided in the area of the channel passed by the dust and dirt particles drawn in, an optical sensor comprising a light transmitter and a coacting light receiver so that the quantity of the dust and dirt particles drawn in at any time is detected. After comparison of the value so determined with a given threshold value, either a visual and/or an acoustic signal are obtained and/or a power variation of the electric motor driving the blower is effected.

Abstract: An alarm system for serving notice of abnormalities such as fire, burglary or other malfunctions has extinction-type separated smoke detectors which detect smoke by exploiting the phenomenon that the intensity of a light beam emitted by a light transmitter toward a light receiver remote from the light transmitter undergoes attenuation due to the occurrence of smoke. The alarm system utilizes the light beam as a carrier for transmitting a signal indicative of an abnormality, thereby reducing the number of line conductors required for signal transmission in this kind of alarm system while signal transmission is rendered less susceptible to the influence of electromagnetic interference. The light transmitter is provided with a signal input circuit composed of an encoder and a serial-to-parallel conversion circuit for receiving the signal to be transmitted and a modulating circuit for modulating a current for driving the light transmitter with the output signal of the signal input circuit.

Abstract: A filter cleaning system for an opacity monitor which has a light source and a light sensor on opposite sides of a first optical path through a gas whose opacity is to be measured, comprises a mechanism for calibrating the opacity monitor during a calibration period and a purging air arrangement for supplying purging air to pipes in the first optical path to keep the interior of the pipes clean. A primary filter is connected to the blower for filtering the purging air. Three-way valves are connected to the input and the output of the blower so that a secondary filter can be utilized to supply clean air in a reverse flow through the primary filter to clean the primary filter. The primary filter is cleaned during this blow-down period at the same time that calibration is taking place for the opacity monitor. In this way, no measuring time is wasted and still the life of the primary filter is extended.

Abstract: Protective device for dust collecting devices, in particular vacuum cleaners such as wheel-mounted or hand vacuum cleaners, whereby the presence of any dust behind the dust collecting vessel, due to a damage to the dust collecting vessel, is detected by means of an electric sensor comprising a light receiver and a light transmitter, and supplied in the form of an electric signal to an associated evaluation circuit. The design of the evaluation circuit is such that when a given threshold value is exceeded it will respond and activate an associated blocking and braking arrangement for interrupting the operation of the vacuum cleaner abruptly. This prevents the collected dust, the quantities of which may be quite considerable, to be blown back within a few seconds into the environment by the continued operation of the dust collecting device in case the dust bag should for example break.

Abstract: A beam divider which is particularly intended for use in smoke measuring apparatus comprises a transparent beam dividing plate (11) which is obliquely arranged in the beam path and is partially silvered at its lower side (11'). Two protective plates (13, 14) which form a closed internal space (12) leave the upper side of the beam dividing plate (11) above and below the optically active region. At least the protective plate (13) which crosses the beam path is transparent and the arrangement is closed in a dust-tight manner at the end faces.

Abstract: A smoke detector contains two radiation transmitters and two radiation receivers. Each of the radiation transmitters emits in a different spectral region, for instance, one emits above and the other one below 600 nm. One part of the radiation of both radiation transmitters is conducted via a measuring path, which is accessible to smoke, to one of the receivers constituting a measuring radiation receiver, and another part of such radiation is conducted via a comparison path, which is not accessible to smoke, to the other of the receivers constituting a comparison radiation receiver.

Abstract: An aerosol detector, for instance a transmission measurement path in a measurement chamber, is provided for the detection of a foreign component in a gas, for instance of incendiary aerosols or smoke in air, and communicates with a reference chamber containing aerosol-free reference gas. The gas in the measurement chamber is periodically exchanged for uncontaminated gas from the reference chamber by a periodical volume alteration of the reference chamber so that, in the presence of aerosols, the aerosol concentration in the measurement chamber and the output signal of the aerosol detector are modulated. The modulation, i.e. the variable portion of the output signal, is an indication of the aerosol concentration or the smoke density. A particularly suitable application is smoke detection in air for the purpose of fire or incendiary reporting or for monitoring air pollution.

Abstract: Apparatus for controllably admitting a sample volume of engine exhaust into a bifurcated, closed-loop opacity chamber and wherein the exhaust sample is controllably directed away from the internal optics via symmetric flow inducing air guides. A pulsed light source is controllably directed through the opacity chamber and exhaust sample and the detected light is compared to a reference level so as to determine a relative measure of the sample's opacity. Attendant control circuitry permits the selected display of corresponding sample opacity and density values.

Abstract: A measuring system for the detection of particles in a gas flow utilizes a light source, a light detector for receiving light from the light source, and an evaluating circuit connected to the light detector. A hollow body having a longitudinal portion and a side portion which branches off from the longitudinal portion at an angle is provided. One end of the longitudinal portion is open for entry of the gas flow and an end of the side portion is open for exiting of the gas flow. The other end of the longitudinal portion is closed with a cover in which the light source and light detector means are arranged. Particles which might be present in the gas are deposited on inner walls of a bore hole in the cover so as to change detected intensity of the light from the light source which passes through soiled areas at the inner wall of the bore hole.

Abstract: A light transmitter transmits a beam of light along a measurement path to a light receiver which receives the light beam either directly or via a retro-reflector. The light receiver forms electrical signals representative of the transmission or absorption along the measurement path. In an arrangement with separate light transmitter and receiver units these units are arranged in respective housings at each end of the measurement path. In an alternative arrangement in which the light transmitter and receiver are in a single unit a retro-reflector is positioned at the other end of the measurement path. In this alternative arrangement the light transmitter/receiver unit is embodied in one housing and the retro-reflector in a second housing. In either arrangement both housings are sealingly closed by at least one and preferably two windows which can be moved cyclically into and out of the light beam.

Abstract: A gas analyzer capable of measuring select properties of gas includes a source for emitting a beam of radiation and a detector for receiving the radiation, with the beam aligned to impinge the detector. A housing for enclosing the beam has two apertures permitting the gas to enter the housing through one of the apertures to intercept the beam, and to exit from the housing through the other aperture. Nozzles capable of generating fluid curtains are positioned to intercept the beam and are positioned to define a zone in the housing within which zone the gas is confined.

Abstract: Installation to measure the limit of visibility in a fog, comprising a motor of a control device effecting the setting of the variable focus of the optical apparatus (1) and simultaneously driving one or several moving assemblies (8) displaceable with respect to one or several stationary assemblies (9). In each combination of a moving assembly (8) and the corresponding stationary assembly (9), one of the two assemblies comprises at least one detector (11) or sensor (12) of numerical and/or analog information consigned to the other assembly and having as its object the light of the series of lights upon which the variable focus is set.

Abstract: The environment within an area is monitored through use of tomographic reconstruction techniques. Signals for use in the tomographic reconstruction are generated optically by a laser which transmits signals to reflectors positioned about the area and then to detectors around or within the area. Several embodiments illustrate the method whereby the signals are generated by sequential illumination of detectors or by simultaneous illumination of detectors.

Abstract: In a photoelectric detector having a light transmitting section and a light receiving section disposed remote from each other, intermittent illumination of a light source of the light transmitting section is detected and processed by the light receiving section in synchronism with the intermittent illumination by way of power lines interconnecting the light transmitting and light receiving sections. To this end, a circuit for intermittently supplying a power source to the light transmitting section is provided in the light transmitting section or the light receiving section and the intermittent power supply is utilized as a synchronizing signal to intermittently illuminate the light source and to allow the light receiving section to transmit and process a received light signal or a signal based thereon in synchronism with the intermittent illumination.

Abstract: In the smoke opacity monitor disclosed herein, a measurement of opacity is obtained by measuring the proportion of polarized light from the background sky which is detectable through the smoke plume. Compensation and normalization is provided to minimize errors generated by illumination of the plume itself and for the overall intensity of the background sky light.

Abstract: In a photoelectric smoke sensor which produces a fire alarm signal when an amount of attenuation of received light exceeds a predetermined level due to smoke flowing into a space between light emitting and light receiving devices, the level of a receiving light signal from the light receiving device is converted by a converting level control signal. An initial value of the receiving light signal is converted into a digital quantity which is stored in a memory circuit. The digital content of the memory circuit is then converted into an analog quantity. The analog quantity is then compared with the level-converted receiving signal to produce a fire alarm signal. The analog quantity and the level-converted receiving signal are compared with each other at a predetermined period to correct the converting level control signal when there is a difference between the analog quantity and the level-converted receiving signal as a result of the comparison.

Abstract: A circuit for reducing or eliminating the sensitivity of alarm circuitry to false alarms caused by noise occurring synchronously with a 60 Hz line voltage. The 60 Hz line signal is applied to a variable-threshold circuit which produces a 60 Hz clock signal. The clock signal produced by the variable-threshold circuit may be selected to occur at different points during a cycle of the 60 Hz line signal. In response to successive alarm signals, the clock signal produced by the variable-threshold circuit occurs with different phasing relationships to the 60 Hz line signal. Before an alarm indication is made, an alarm signal must be provided by the smoke sensor in response to a plurality of successive samples.

Abstract: An apparatus and a method for standardizing a gas measuring device has a source capable of emitting a beam of radiation aligned to impinge a detector and gas particles. A hollow, open-ended tube is used as a standardization means and is placed adjacent to the beam. The tube can be moved to enclose the beam, to prevent the gas from intercepting the beam, and to transmit substantially all of the radiation from the source to the detector.

Abstract: A sample chamber for a gas analyzer for use in a duct containing gases to be analyzed is disclosed and includes a flow directing apparatus formed by a pair of spaced members which form a passage therebetween in the form of a converging diverging throat and an outer housing at least partially surrounding the flow directing apparatus. This outer housing has at least a pair of apertures and is movable by a suitable apparatus between one position in which the outer housing apertures are generally aligned with the flow directing passage and another position in which the outer housing apertures are spaced from the passage with non-apertured portions of the outer housing positioned across the ends of that passage.

Abstract: In a duct having a gas of predetermined density and viscosity flowing therethrough at a predetermined velocity, a sample chamber for a gas analyzer for use in such a duct is disclosed and includes an inner chamber having a passage therethrough and an outer chamber at least partially surrounding the inner chamber and having a pair of apertures, with the outer housing being movable by suitable apparatus between one position in which the outer housing apertures are generally aligned with the inner chamber passage and another position in which the outer housing apertures are spaced from the inner chamber passage, the outer housing and inner chamber being configured and dimensioned such that the Reynolds number for the flow of duct gases over the outer housing and inner chamber is sub-critical when the outer housing is in its other position with its apertures spaced from the inner chamber passage.

Abstract: A photo-electric smoke detector operating on the reflected light principle which has a rate detector for detecting the rate of increase of smoke concentration. When the rate exceeds a predetermined value, the rate detector causes the intensity of the smoke detector light source to increase, thereby increasing the sensitivity of the detector. In one embodiment of the invention, after the intensity of the light has been increased by the rate detector, it is maintained at the higher intensity for a predetermined time, even if the rate of increase of smoke concentration falls below the predetermined value.

Abstract: Disclosed is a method and apparatus for calibrating and recalibrating a photometric measurement instrument which supervises the presence of dust in a particular location as produced by a process during which dust is developed on an irregular basis. The method is characterized in that the calibration is initiated upon the detection of a condition in which dust concentration is expected to be low. In a steel-making process, such a condition occurs upon termination of the blowing phase of a converter. In the case of smoke in a flue, such a condition occurs when there is an absence of gas flow in the flue.

Abstract: Miniaturized smoke detectors, which operate on a light obscuration principle and may be either AC or battery operated, are both optically and electrically balanced whereby an unbalance resulting from the presence of smoke will trigger an alarm. The smoke detectors are characterized by a smoke chamber in which a light emitting diode and a pair of light detectors are installed in a manner which precludes relative movement therebetween. A splitter plate is also installed in the smoke chamber whereby both detectors are caused to see the same light flux density and one of the detectors, positioned in close physical proximity to the light source, acts as a reference signal source.

Abstract: A smoke detector system utilizing remote detectors of the photo-electric type connected to a central control panel. In one embodiment means is provided for monitoring both the signal lead and power lead, and in another embodiment, means is also provided for monitoring the condition of the detector light source. A normally illuminated compensating cell is provided in series with the smoke detection cell, with the bottom of the compensating cell being maintained a predetermined voltage above ground to provide a monitor voltage at the junction of the cells. The output signal lead is connected to the junction of the compensating cell and the smoke cell, and feeds a high impedence input amplifier, the output of which goes to the control panel. Means is provided at the panel for responding to the presence of an alarm signal on the signal lead or the absence of the monitor voltage which might be caused by a break in the signal lead, or the power lead.

Abstract: A light scattering type smoke detector having an improved labyrinth high in shielding effects for interior detecting means from the exterior light and other obstacles such as dusts, insects or the like than smoke particles is provided. The labyrinth comprises a plurality of outer peripheral shielding elements spaced from one another defining peripheral apertures therebetween, a plurality of inner shielding elements spaced from the outer elements and from one another defining therebetween inner apertures, said inner shielding elements opposing respectively to each peripheral aperture and said inner apertures to each outer shielding element, and a filtering means made of thin plate material perforated to have many small holes and disposed behind the respective outer elements to close the inner apertures while allowing substantially the smoke particles only to pass therethrough.

Abstract: This invention relates to a calibrated oil burner filter paper on which is imprinted or otherwise processed a pre-selected geometrically shaped standard gray smoke scale and its integral use with an oil burner smoke tester and dispenser to provide a paper record for a quick and accurate visual analysis of the smoke density of a test smoke spot of the flue gases from burning distillate fuels, and also in the subsequent determination of the "Smoke Spot Number" of the flue gases by visually matching the shade of the test smoke spot lying in juxtaposition with the most like shade of a sector of the said imprint of a pre-selected shaped standard smoke test scale. .Iadd.