Abstract: The invention relates to a polymer composition comprising pH-sensitive fluorescent dyes, to an ionic strength-independent optical sensor for pH value determination that contains the composition in the form of a membrane on a transparent support material, and to an optical process, according to the fluorescence method, that renders possible highly accurate pH value determination independently of the ionic strength of the test solution. The process is especially suitable for the determination of the pH value of physiological solutions, especially for the determination of the pH value of blood.

Abstract: A light emitting diode 1 and a condenser lens 2 are arranged in an optical axis direction. In the light emitting diode 1, a cover 4 having a tip end lens 5 is attached to one side of a main unit base 9, a light emitting chip 6 is supported by a bonding wire 8 drawn out from the body base 9 inside the cover 4, and a reflector 7 is placed behind the light emitting chip 6. With respect to a first light source of the light emitting chip 6, the position where light which is forward reflected by the reflector 7 impinges on the tip end lens 5 is set as a virtual second light source 10, and the focal point of the condenser lens 2 is set at the position of or in the vicinity of the position of the second light source 10.

Abstract: A method and apparatus is provided for detecting airborne particles in an electronic enclosure. The electronic enclosure may be used to house one or more electronic devices or components of an electronic system, such as a computer or data storage system. A particle detection system is provided to monitor the air within the enclosure and to generate an alarm signal in response to detection of a threshold level of airborne particles within the enclosure that is indicative of an operational anomaly associated with at least one of the electronic devices or components. In response to the alarm signal, the electronic devices housed within the enclosure may be automatically shut down to reduce potential damage to at least the devices housed within the enclosure. The detection system is particularly suited for detecting the presence of smoke within an electronic enclosure, such as may be generated during a combustion event by overheated or electrically shorted electronic components.

Abstract: A smoke alarm on the scattered radiation principle. Having a measuring field (5), accessible to smoke particles, in a measuring chamber, at which field the radiation direction of a radiation transmitter (6) is aimed, and scattered radiation occurring in the measuring field (5) can be received by a radiation receiver (7); the measuring chamber includes a portion of the hollow ellipsoid (3) which is mirror-coated on the inside; the measuring field (5) is disposed at the first focal point (1) of the hollow ellipsoid; the radiation receiver (7) is disposed at the second focal point (2) of the hollow ellipsoid (3).

Abstract: A smoke detector includes a housing defining a dark chamber admitting test atmosphere. A light receiver is disposed within the chamber. A scatter emitter is positioned within the chamber such that light strikes the receiver when reflected off particles suspended in the test atmosphere. An obscuration emitter is positioned within the chamber such that light emitted is directed to the receiver unless obstructed by particles suspended in the test atmosphere. A smoke detect signal is generated responsive to a measurement made responsive to the scatter emitter and/or the obscuration emitter.

Abstract: A detector includes a sensor of an ambient condition. Outputs from the sensor are sampled at a predetermined rate when the outputs do not represent an alarm condition. The outputs are analyzed using pattern recognition techniques to determine if a predetermined profile, which precedes the presence of an alarm condition, is present. In the event that the profile is detected, the sample rate is increased along with associated sample value processing. The detector includes a programmable processor coupled to the sensor. The processor includes pattern recognition instructions for detecting the presence of the predetermined profile. The processor also includes instructions for altering the sampling rate in response to the detected presence of the profile. A second sensor can be incorporated to provide sample rate altering signals.

Abstract: A scattered light fire detector and a method for evaluating scattering signals of a fire detector are disclosed. The microprocessor-based scattered light fire detector measures the scattering signals at two scattering angles and determines an alarm threshold. An alarm value is determined as a function of the ratio of the scattering signals and compared with the determined alarm threshold. The fire detector can be used with mixed fires without prior calibration. Fraudulent measurement values arising, for example, from water vapor can be stored in a memory.

Abstract: A smoking detection device comprising a smoke sensor for generating an electrical signal in response to the detection of smoke, and an optical sensor for generating an electrical signal in response to the detection of ultraviolet radiation in a prescribed range. The smoking detection device may further comprise an alarm unit which is electrically connected to the smoke and optical sensors for generating an alarm signal in response to any one of the electrical signals generated by the smoke and optical sensors. The optical sensor is configured to sense ultraviolet radiation in a spectral range of from about 185 nanometers to about 260 nanometers, and of an intensity in a range of about 1 picowatt per square centimeter to about 1 nanowatt per square centimeter.

Abstract: The fire detector for sensing a fire, comprises; a smoke chamber, a light emitting element, and a light detecting element for detecting a scattered light caused by scattering a light emitted by the light emitting element with a smoke which enters in the smoke chamber, wherein a wall part of the smoke chamber is formed in a shape based on a circle having a predetermined size, and comprises a projecting portion which projects from at least a part of the circle to an outside of the circle, the light emitting element is disposed on the projecting portion of the smoke chamber, and the light detecting element is arranged out of the smoke chamber and an optical axis thereof is approximately perpendicular to a plane including the circle.

Abstract: A smoke detector (2) which operates on the scattered light principle comprises a detector chamber (4) through which a light beam (10) passes. A series of collimator discs (24, 26, 28) with apertures of progressively increasing size are associated with the light source (6) to prevent glints of light from entering the zone of the chamber at which detection occurs as a result of the presence of scattered light induced by the presence of smoke particles. A light absorber (12) at the end of the detector chamber remote from the light source uses a target surface in the form of an asymmetric cone (42) onto which the beam is directed. The design of the collimator discs and light absorber reduce the occurrence of stray light, leading to increased sensitivity.

Abstract: An aspirated-type detector includes a housing with an internal ambient condition sensing region and a sensor carried therein. The housing is perforated with ambient atmosphere inflow ports. A fan or similar device lowers the pressure in the internal region thereby producing a positive inflow of adjacent, external ambient atmosphere into the sensing region. Alternatively, the fan can be operated to inject exterior ambient atmosphere into the sensing chamber under positive pressure. The fan can also be modularized. The detector can incorporate control circuitry for supervisory or signal processing purposes.

Abstract: An improved fire detector is obtained by combining a conventional smoke particle sensor with a fire radicals odor sensor; the latter being an electronic nose tuned to respond to the presence of a family of radicals, produced by most fires, that is responsible for the odor associated with a fire. The conventional smoke particle sensor is prevented from producing an alarm signal unless the tuned electronic nose senses that the fire-produced radicals are increasing at a rate that exceeds a preset threshold rate. In another aspect of the invention, the smoke particle sensor is provided with a second, lower, threshold connected to a timer so that an alarm will be produced if the lower threshold is exceeded, without interruption, for a preset time. The improved fire detector, using the combined sensors, has greater sensitivity and a lower false alarm rate.

Abstract: An alarm signaling device (10) that is operable to produce an alarm signal in a room when triggered by a fire alarm control panel. The signaling device includes a silencing circuit (24) that can be activated by a person in the room to temporarily extinguish the alarm signal. The silencing circuit includes a timing circuit (30) and a switch (32) consisting of a pair of touch contacts (38, 40) that are activated by body resistance.

Abstract: A fire and smoke detector utilizes a statistical analysis of the near infrared radiation incident on it. The spectral radiation intensities incident on the fire detector are continuously measured at two near-infrared wavelengths, and a time series of apparent source temperatures is obtained from these measurements. The power spectral density and the probability density function of the apparent source temperatures are sufficient to determine the presence of a fire in the vicinity of the detector. The detector can indicate the presence of a fire in an adjoining room from the radiation which is incident on it due to reflections from common building materials. The present invention relates to fire and/or smoke detection methodology and associated apparatus. The detector utilizes fiber optic as a viewing and absorption/scattering detection means.

Abstract: A fire detector is equipped with a smoke detector and electrical circuitry for declaring a fire alarm if a smoke concentration based fire detection criteria is satisfied. A CO.sub.2 detector is included in the fire detector for forming an a priori estimate of the probability of the existence of a fire. If the a priori probability rises above a predetermined level, the smoke concentration base fire detection criteria of the smoke detector are altered to allow the more rapid detection of a fire.

Abstract: A driving unit generates a driving current corresponding to a light generation control signal CTL supplied from a light generation controlling unit. The driving current is supplied to an LED. Light emitted from the LED impinges on a light receiving circuit through a space of a monitoring area. The received light level of the light receiving circuit is converted into a received light level signal RLV in an A/D. The received light level signal RLV is supplied to a smoke detecting unit and the light generation controlling unit. The received light level signal RLV is monitored in a short period by the smoke detecting unit. When the received light level signal RLV is equal to or lower than an alarm level, an alarm signal ALM is output. The light generation controlling unit compares the received light level signal RLV with a reference level in a long period.

Abstract: A wireless integrated smoke detector and temperature monitoring device. The device comprises a photoelectric sensor for determining the presence of smoke, thermistor for providing a temperature signal reflective of the temperature level, processing means for monitoring the smoke and temperature, and transmission means for transmitting messages to the alarm system controller. Rather than transmitting the actual temperature to the system controller, the transmitter transmits a status message which comprises status bits for low temperature trouble condition, smoke or heat alarm, and also low temperature trouble condition with smoke or heat alarm. To conserve battery power, the device alternates between a sleep mode and a wake mode. During the wake mode the trouble conditions are checked by the processor and if necessary, a status message is transmitted.

Abstract: A light source image, i.e., a near field pattern of the light-emitting face of a laser diode which emits laser light having the electric field component in a predetermined direction is formed by an imaging lens at an image forming position of a smoke detecting area through which a flow of sucked air passes. A light receiving device is disposed on an optical axis which passes through the image forming position of a light source image in the smoke detecting area and which is set in a plane that is substantially parallel to the direction of the electric field component of the laser light, and receives scattered light due to a smoke particle passing through the imaging position of the light source image and the vicinity of the imaging position.

Abstract: Smoke alarms that incorporate dust repelling screens exhibit improved performance with fewer false alarms. Effective screens include conductive strands combined with non-conductive elements.

Abstract: A smoke sensor includes a light receiving unit for temporally alternately receiving scattered light of two different wavelengths .lambda..sub.1 and .lambda..sub.2 ; a calculating unit for performing a calculation required for smoke detection, on a scattered light output y of the wavelength .lambda..sub.1 and a scattered light output g of the wavelength .lambda..sub.2 from the light receiving unit; and a smoke detection processing unit for performing a smoke detection process on the basis of a calculation result output from the calculating unit. The calculating unit estimates an output value of one of the scattered light output y of the wavelength .lambda..sub.1 and the scattered light output g of the wavelength .lambda..sub.2 at a sample timing of the other output, and obtains a ratio of the estimated output value of the one scattered light at the sample timing of the other output to an output value of the other scattered light, as a two-wavelength ratio.

Abstract: A light beam is directed from a light source through an air sample 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 air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. A light focusing lens in front of the light source is arranged to focus the unscattered part of the light beam onto the blocking device. Light transmitted through the blocking 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. The signal may be used to activate filtering or air conditioning devices.

Abstract: An ultraloud ambient condition detector incorporates a sensor in combination with a control circuit. An alarm indicating signal from the control circuit energizes a multi-frequency drive circuit which produces a band of output frequencies usable to drive a piezoelectric output element. The output element has one or more resonant frequencies which fall within the band of the drive frequencies. A feedback circuit is provided to maintain the unit in an alarm state, after it has switched into that state, even if the input ambient condition indicator signals a decline in the value of the sensed ambient condition or in the presence of noise perhaps generated by the audio output device. A high current, low duty cycle battery test current repetitively loads the battery consistent with current load when the detector is in an alarm state.

Abstract: An allergen particle detecting apparatus has a sample area through which environmental air is directed. A light beam is directed through the air sample 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 air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. Light transmitted through the blocking 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 fire detector capable of readily and accurately adjusting the sensitivity there of 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: An allergen particle detecting apparatus has a sample area through which environmental air is directed. A light beam is directed through the air sample 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 air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. Light transmitted through the blocking 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: An ambient condition detector includes a sensor for a first ambient condition and a second, sensor which is responsive to a second ambient condition not necessarily correlated to the first condition. Control circuitry, coupled to both sensors, processes an output from the first sensor to reduce transients and/or noise therein which are not correlated to the first ambient condition. Processing characteristics are altered in response to an output from the second sensor. The processing can take place at the detector or, in part, at the detector and, in part, at a displaced, common control element.

Abstract: A fire detector with a maximum average response time of less than 1.5 minutes is obtained by combining a smoke detector with a CO.sub.2 detector that uses NDIR sensor technology. The smoke detector is used to detect smoldering fires and to help prevent false alarms attributable to the CO.sub.2 detector. The CO.sub.2 detector is used to rapidly detect fires by measuring the rate of change of CO.sub.2 concentration. A signal processor generates an alarm signal when a smoldering fire is detected or alarm logic indicates that a fire has been detected.

Abstract: A surveillance device, e.g. a fire alarm or an intrusion detector, includes a mount having a connector block, and an insert having a sensor assembly, a printed circuit board with evaluation electronics, and an electrical contact to the connector block. The printed circuit board is a plug-in card with a contact strip. For insertion, with the mount disposed at a horizontal surface, for example, the insert is first moved vertically and then displaced horizontally. In the horizontal displacement, an electrical connection is established between the contact strip and the connector block.

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: An aspirated-type detector includes a housing with an internal ambient condition sensing region and a sensor carried therein. The housing is perforated with ambient atmosphere inflow ports. A fan or similar device lowers the pressure in the internal region thereby producing a positive inflow of adjacent, external ambient atmosphere into the sensing region. Alternatively, the fan can be operated to inject exterior ambient atmosphere into the sensing chamber under positive pressure. The fan can also be modularized. The detector can incorporate control circuitry for supervisory or signal processing purposes.

Abstract: The pulse width of a light reception pulse signal a from a light receiving device is detected, and the smoke density is detected based on a total pulse width of pulse widths per unit time period. Alternatively, the smoke density may be detected based on an integrated value of the light reception pulse signal a from the light receiving device per unit time period. Even if the flow rate of the sucked air is varied, the total light reception pulse width value per unit time period is not varied, so that the smoke density can be accurately detected.

Abstract: The smoke detecting apparatus of the present invention comprises a detection space (52) into which generated smoke is to be introduced; light-emitting means (2) for emitting a predetermined coded light pulse train into the detection space (52); light-detecting means (3) for detecting scattered light which is generated when the light emitted from the light-emitting means (2) is scattered by the smoke and generating an electric signal corresponding to the detected light; and control means (4) for generating a burst code signal composed of a pulse train coded with a reference pulse to the light-emitting means (2) and judging that the smoke exists in the detection space (52) when the pulse patterns of thus compared signals coincide with each other. According to this configuration, the apparatus can securely operate at the time of smoking and cannot detect when there is no smoke.

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: The device for detecting the presence of smoke includes a dark chamber which receives the smoke to be detected, a source suitable for emitting into said chamber a light pencil made up of short duration pulses spaced apart from one another by identical much longer periods, a detector suitable for generating response signals associated with the smoke reflecting part of the successive light pulses, and means for comparing said signals with a threshold and for triggering an alarm in the event of said threshold being exceeded by a plurality of said successive signals. The device further comprises means for automatically increasing the frequency at which said pulses are emitted from the first occasion on which a signal exceeding said threshold is detected, the alarm then possibly being triggered, as a function of the signals generated by the detector in response to a plurality of successive pulses emitted at the higher frequency.

Abstract: A device is disclosed for measuring light scatter by particles (3) suspended in a carrier medium with a view to ascertaining the density, size or size distribution of the particles. The device comprises: at least one light source (8) which directs light onto a light-scattering center (2) in the carrier medium with the suspended particles (3); a receiver (4) to pick up a portion of the scattered light from the light-scattering center; and an evaluating device connected downstream of the receiver (4). The invention provides for an elongated detection chamber bounded radially around its central axis by the wall of a housing (1) which also acts as a duct for the through-flowing carrier medium with the suspended particles (3). Each light source (8) is mounted on the wall of the housing (1) and points toward the central axis of the detection chamber.

Abstract: A fire detection system (10) includes a smoke detector (52) that measures smoke particle density indicative of smoldering fires and a CO.sub.2 detector (90) that measures CO.sub.2 concentration indicative of flaming fires. In a first operating current saving method, the smoke detector is operated at a normal PRF while the CO.sub.2 detector is operated at a very slow PRF. Smoke density measurements (14) produced by the smoke detector are compared with a set of tentative fire detection criteria (18, 20, 22, 14), and if met, the CO.sub.2 detector PRF is substantially increased to rapidly produce CO.sub.2 concentration measurements (26) that are compared to a set of conclusive fire detection criteria (30, 32, 36, 38). In a second operating current saving method, the CO.sub.2 detector is operated at a normal PRF while the smoke detector is operated at a zero PRF. CO.sub.2 concentration measurements produced by the CO.sub.

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 relative angle detecting system permitting a wider range of detectable angles and offering a small detection error by using polarization and a virtual reality providing system using the same are disclosed. The relative angle detecting system includes a light source having a given polarizing direction and a light reception unit in which a plurality of polarization filters having different polarizing directions other than 90 degree and a plurality of light-receiving devices for receiving light passing through the filters are incorporated, and a relative angle is calculated on the basis of a combination of strengths of output signals of the plurality of light-receiving devices.

Abstract: The invention provides a self-contained automatic fire detection, warning, and suppression life safety system having an extinguishant source and a fire detector coupled to an electronic processor. The processor has logic to interface with components for detecting and warning of a fire and releasing the extinguishant. Self-diagnosis logic checks the entire system's function, pressure, power level, and power source. Additional sensors are provided for detecting various hazards, and the processor has logic for proper response.

Abstract: A smoke detector (10) has internal self-adjustment and self-diagnostic capabilities. It includes a microprocessor-based alarm control circuit (24) that periodically checks the sensitivity of a smoke sensing element (20) to a smoke level in a spatial region (12). The alarm control circuit and the smoke sensor are mounted in a discrete housing (25) that operatively couples the smoke sensor to the region. The microprocessor (30) implements a routine (50) stored in memory (32) by periodically determining a floating adjustment (FLT.sub.-- ADJ) that is used to adjust the output (RAW.sub.-- DATA) of the smoke sensing element and of any sensor electronics (40) to produce an adjusted output (ADJ.sub.-- DATA) for comparison with an alarm threshold. The floating adjustment is not greater than a maximum value (ADJISENS) or less than a minimum value (ADJSENS). Except at power-up or reset, each floating adjustment is within a predetermined slew limit of the immediately preceding floating adjustment.

Abstract: A detector sensor system for sensing the presence of a toxic gas, such as carbon monoxide and/or smoke whereby a corresponding alarm is sounded. The presence of the gas is detected by passing light through a biomimetic sensing material in which the optical characteristics change in the presence of the target gas. This system includes a housing containing a light emitter, light detector and a mechanism for sounding an alarm. The sensing material is contained in a cell which, together with a battery to power the system, is mounted in a key insertable into the housing. The key may be readily inserted or withdrawn from the housing for replacement purposes. When fully inserted, the key positions the sensing cell means between the light emitter and detector means and brings the battery contacts carried therewith into connection with contacts associated with the system circuitry mounted within the housing.

Abstract: A smoke detector incorporates a porous plastic material which carries a hydrophilic agent alone or in combination with a surfactant which can be sprayed or deposited onto structural elements of the detector. The detector can include a molded removable plastic element that carries a hydrophilic agent. The element can be arranged to surround a light beam injected into a sensing region of a photoelectric detector.

Abstract: A fire detection system provides multiple levels of signal processing so as to minimize the effects of noise from various sources. In a first level of processing any DC bias in signals received from detectors is removed. In a second level of processing, signal values from current sample times for a given detector are compared to one or more prior sample values from that detector for purposes of removing large transient pulses due to dust particles and the like. In a third level of processing, high frequency noise, perhaps from electrical sources, is filtered from the representation of the signal. Finally, the fully processed signal value is compared to one or more threshold values so as to make a determination as to the presence or absence of a pre-alarm or a fire condition.

Abstract: A smoke detection unit has a detection chamber for sampling smoke from a surrounding environment. The detection chamber allows air circulation but is optically opaque. This configuration is typical of photoelectric smoke detectors, for example. A housing defines a window though which air from the environment circulates into and out of the detection chamber. The window's height is approximately the same as the chamber. A cage vane is positioned in the window and is configured as an inverted frustoconical member. An inner edge of the cage vane is spaced away from the chamber. The angled vane, along the other aspects of the unit's configuration, improves sensitivity by increasing smoke circulation through the chamber. This configuration guides the air currents typically created by fires at the ceiling so that the smoke flows easily into the detection chamber.

Abstract: A projected beam-type smoke detector and receiving unit includes in its light receiver data output unit 118 for outputting serially status information and status signal output units 85, 86 for sending the status information to the receiving unit, and in its receiving unit 30 data examining unit 113 for examining sequentially the status information. The light receiver 31 also includes a pulse generator unit 82 for generating pulses having different pulselengths according to the type of alarm information, and photoelectric converter units 83, 84 for sending to the receiving unit 120 the pulses of different pulselengths generated by the pulse generator unit 82. The receiving unit 120 includes a pulselength determining unit 108 for determining the type of alarm information from the pulselength of the pulse sent by the projected beam-type smoke detector and display units 110, 111 for displaying the alarm information type determined by the pulselength determining unit 108.

Abstract: A corrosive gas detecting sensor has a cartridge, a sensor body, and a connecting unit. The cartridge has a sensor element and a memory device. The sensor element changes its characteristic property when the sensor element contacts a corrosive gas, and the memory stores an initial value of the characteristic property of the sensor element. The sensor body has a control unit which detects a change of the characteristic property of the sensor element when the cartridge is connected to the body and outputs an indication of a fire when a rate of the change exceeding a preset reference value, the cartridge is detachably attached to the sensor body. The connecting unit electrically connects the cartridge with the sensor body when the cartridge is attached to the sensor body.

Abstract: A multiple sensor smoke detector includes at least an ionization and a photoelectric sensor. Outputs from the sensors are fed to circuitry for generating continuously variable coefficients. One coefficient corresponds to each sensor output. Respective coefficients and sensor outputs are multiplied in multiplier circuitry to produce processed outputs. The processed outputs are combined in a summing circuit to produce at least one output value indicative of a level of detected smoke. The coefficient generating circuitry, the multiplier circuitry and the combining circuitry could be implemented in a programmed microprocessor. The coefficient generating circuitry could be implemented using prestored membership functions indicative of various types of fires.

Abstract: The present invention provides for a smoke detection chamber and a photoelectric smoke detector containing the smoke detection chamber. The smoke detection chamber has side walls with openings provided therein for ingress and egress of smoke particles, a top and a bottom. A photoemitting diode is mounted in a mounting arrangement in the side wall of the smoke detection chamber to transmit a light beam across the smoke detection chamber without directly impinging upon either the top or the bottom surfaces. The bottom of the smoke detection chamber has an opening with a shielding arrangement thereabout open to the chamber located between the centerline of the smoke detection chamber and the mounting arrangement in the side wall of the chamber.

Abstract: Self-contained smoke detector systems each have internal self-diagnostic capabilities and function as components of an automatic fire alarm communication system implemented with a conventional two-wire alarm initiating circuit. Each system includes a microprocessor-based self-diagnostic circuit that periodically checks sensitivity of radiation sensor electronics 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 determines whether and provides a sensitivity fault condition signal indicating that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits.

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.