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 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: Method and apparatus for the detecting hazardous conditions including the hazardous leakage of carbon dioxide gases by detecting spontaneously a plurality of the conditions which are encoded with a different response for each condition; for the detection of hazardous conditions associated with combustion or potential combustion, the detection is of a plurality of gaseous conditions having different chemical and thermal characteristics and the presence of each such condition is indicated; when the detection is of the leakage of fuel gases, a plurality of catalytic units is used, each having a platinum wire extending to a junction with a comparator and bridged by a detector provided with bridge balance and threshold adjustment; periodic heat cleansing is by a multi-terminal bistable oscillator; smoky carbon particles are detected by an ionization chamber connected to alarm circuitry.

Abstract: This invention is a method for determining when combustion cans or turbine blades are failing in gas turbine engines. It measures the specific ions emitted by hot spots of can and blade material when they have failed or are failing. The invention relies on the electromagnetic energy radiated by ions that are created as combustion gas erodes and ionizes the materials in these hot spots. Acceleration by the earth magnetic field and by acoustic and mechanical forces normally present in combustion machinery cause these charged particles to radiate identifiable electromagnetic emissions. The frequency of the radiation, being a function of the charge and mass of the particles, allows free ions in the exhaust stream to be identified. The device operates by measuring the electromagnetic spectrum and relating detected frequencies to the mass of the ions from can liner and blade materials. The device can be used in fixed installations such as power plants, ships and aircraft.

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 compensated ionization-type sensor includes spaced apart active and reference electrodes. A center electrode is disposed between the active reference electrodes. A compensating electrode is disposed adjacent to the center electrode and, capacitively coupled thereto. The compensating electrode is electrically coupled to the active electrode. A compensating screen with a selected potential applied thereto surrounds the electrodes to compensate for velocity of the ambient atmosphere.

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: 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: An ionization type smoke detector includes a smoke detecting section including an intermediate electrode and an outer electrode to confine an outer ionization chamber therebetween into which smoke to be detected is introduced, and a reference resistance section for forming a reference resistance with respect to the outer ionization chamber, and a sensor output section including a first transistor with its gate connected to the intermediate electrode, and a serial circuit connected to a source of the first transistor and consisting of a first fixed resistor and a first constant-current circuit having a first variable resistor for output adjustment, the sensor output section producing a sensor output from a junction between the first constant current circuit and the first fixed resistor; a fire discriminating section including a reference voltage generating circuit having a second variable resistor for reference voltage adjustment, the fire discriminating section producing a discrimination output when the senso

Abstract: The present invention relates to an improvement of an ionizing smoke sensor having one radiation source and a two chambered structure consisting of an internal ionization chamber housing an internal electrode having a radiation source and defined by an intermediate electrode, and an external chamber where smoke can flow in, defined by an external electrode and irradiated from the radiation source through an opening in the intermediate electrode. Hitherto, in an ionizing smoke sensor having one radiation source and a two chambered structure, there has been a problem in that the giving of misinformation and noinformation occur when a little amount of thread, moisture or dust invades or a current of air flows an internal ionization chamber through an opening and an external ionization chamber. In addition, the electric field in the internal ionization chamber loses its homogeneity because of the opening, hence V-I characteristics preferable for the internal ionization chamber can not be obtained.

Abstract: An ionization fire detector of the type including a measuring chamber and a reference chamber having a common electrode which is connected to the gate terminal of a field-effect transistor by a profile piece of conductive caoutchouc having one end contacting the gate terminal and another end contacting the common electrode.

Abstract: A method for testing smoke sensor is to set a predetermined level for alarm generation on the basis of information on a first output of a main light receiving element for a stray light caused by an emitted light from a main light emitting element, a second output of an auxiliary light receiving element for the emitted light directly received from the main light emitting element and a composite output of the first and second output whereby tests for confirming normal operation and the like of the smoke detector can be executed with high precision.

Abstract: A fire detector system including ionization smoke detectors (7) is provided with improved false-alarm protection. The system includes an ionization chamber (1) with a radioactive source (10), connected in series with a resistor (2) between power supply lines (8, 9), and circuitry (11, 28) for switching the operating voltage of the ionization chamber between a normal operating value (Ut) chosen for maximized detector sensitivity, and an elevated value (Uh) for operation at current saturation. Comparisons involving the ionization currents through the ionization chamber at the two operating voltages are used not only to recognize a condition of partial shielding of the radio-active source (due to condensation, for example), but also to detect smoke under such conditions.

Abstract: A fire alarm system having increased immunity to false alarms comprises control and indicating means (6) and a plurality of ionization smoke detectors (7) connected through signal lines (8, 9, 14) with the control and indicating means (6), each ionization smoke detector (7) comprising an ionization measurement chamber (1) for producing an electrical signal having a characteristic indicative of a monitored condition, a radioactive source (10) to ionize the air in the ionization measurement chamber (1), and an evaluation circuit comprising an amplifier element (3) to amplify the electrical signal from the ionization measurement chamber (1), threshold detection means (15, 16) for comparing the electrical signal characteristic to minimum and maximum limits and for producing an alarm or trouble signal, and electronic means (5, 11) by which the chamber voltage (UK) of the ionization measurement chamber (1) is increased as far as possible to the saturation range of the ionization chamber (1) if the ionization curren

Abstract: A method of the operation of an ionization smoke alarm which has a measuring chamber open to the ambient air and ionizable by a radioactive source. A measuring chamber includes a first electrode to which a supply d.c. voltage is applied and a measuring electrode the potential of which changes in response to the smoke density if smoke enters the measuring chamber. This potential is measured for producing a smoke alarm signal if it reaches a predetermined value. The potential of the measuring electrode is measured for at least one further electric field strength that is compared with at least a second potential which occurs at the second field strength according to the law of the agglomeration of small ions if smoke aerosols are present in the measuring chamber.

Abstract: An ionization-type smoke sensor having a 2-chamber 1-radiation source structure including an inner electrode having a radiation source, an intermediate electrode having an opening through which radiation from the radiation source passes, an outer electrode through which smoke may flow inside from outside, and an insulator supporting and insulating the inner electrode, the intermediate electrode and the outer electrode. In the sensor, a fence portion made of an insulating material is formed on and projecting from a surface of the insulator which faces the outer electrode, the fence portion surrounding the periphery of the opening of the intermediate electrode. By virtue of this arrangement, even when the sensor is subjected to flow of air heading from outside toward the opening of the intermediate electrode, the fence serves to reduce the flow of air heading toward the opening, thereby enabling the characteristics of the sensor chambers to remain stable against flow of air.

Abstract: A fire detector having a first sensor for emitting a first output signal in response to a fire phenomenon, a second sensor for detecting a source of false alarm conditions generated by man and/or machinery and an evaluating circuit. The evaluating circuit has a mechanism for activating an alarm signal when the value of the output of the first sensor exceeds a threshold value. The threshold value is set by the second sensor in response to the detection of signals generated during normal use of the premises to be protected.

Abstract: A system for testing a remotely located sensing unit includes a photosensor located within the sensing unit. A control beam of incident electromagnetic energy can be provided from a remotely located portable source such as a flashlight. Directing the beam of radiant energy from the flashlight against the sensor in the unit causes the unit to initiate a test sequence. The unit can be equipped with a photo-detector to terminate an alarm generated in response to a sensed condition. The unit can include a sonic detector. Control circuitry in the unit can decode a sensed encoded incident beam to minimize false tests or to provide multiple remotely initiated functions.

Abstract: An ionization smoke and fire detector comprises a molded plastic housing that includes a nodal ring for supporting a vibrating plate that is part of an alarm. The alarm may be driven by piezoelectricity or by an electromechanical device. If the detector is battery powered, a portion of the housing is cut out to permit removal and insertion of a battery holder that makes contact automatically upon insertion to supply electric power to the electronic circuit of the smoke detector. One electrode of a reference chamber for the smoke detector is formed by wave-soldering an open metallized area on the printed-circuit board. Contact with the movable element of the alarm and with a high-impedance input in an integrated circuit are made through springs that are not soldered or welded.

Abstract: A smoke and liquid level detector particularly useful for detecting sump pump failure. The detector comprises a sensor head containing two exposed electrodes in electrical contact with two leads which are connected to either side of the ionization chamber of a conventional, ionization-type smoke detector. The sensor head is disposed immediately above the normal water level within the sump well of a sump pump. In case of sump pump failure, the rising water level will immerse the sensor head, causing the electrical contact to be made between the two electrodes, thereby completing a circuit and causing an alarm signal to be sounded.

Abstract: A system for testing a remotely located sensing unit includes a photosensor located within the sensing unit. A control beam of incident electromagnetic energy can be provided from a remotely located portable source such as a flashlight. Directing the beam of radiant energy from the flashlight against the sensor in the unit causes the unit to initiate a test sequence. The unit can be equipped with a photo-detector to terminate an alarm generated in response to a sensed condition. The unit can include a sonic detector. Control circuitry in the unit can decode a sensed encoded incident beam to minimize false tests or to provide multiple remotely initiated functions.

Abstract: An apparatus for indicating an emergency exit in case of fire in a building, includes a smoke alarm apparatus adapted to relay an electrical activating signal causing a luminous exit indicating flag to be projected outwardly from a wall adjacent an emergency exit and near the floor, for indicating exit locations to persons evacuating a smoke filled building.

Abstract: A smoke detector having variable sensitivity to smoke levels and using one button both to test the smoke detector and actuate a mode of diminished sensitivity to smoke levels. The smoke detector is operable in a normal sensitivity mode and a diminished sensitivity mode with rapid switching between the modes. The sensitivity to smoke levels is substantially constant when in either the normal or diminished sensitivity mode.

Abstract: A modular smoke detector is adapted for mounting in an electrical equipment cabinet. The smoke detector module is of a standard size and configuration, thereby facilitating mounting anywhere in the cabinet. A mounting location near the bottom of the equipment cabinet is preferred to better detect the heavier than air combustion products of smoldering or burning insulation. The modular smoke detector includes a commercial ionization type detector and a fan. The fan induces air from the interior of the equipment cabinet into the module. The fan is positioned such that it does not discharge directly onto the ionization detector to prevent excessive speed of the air through the ionization detector.

Abstract: An environmental abnormality detection apparatus includes a detector for detecting environmental changes by monitoring physical changes in the environment and generating an output signal upon the detection of such an abnormality, a signal processor which generates an environmental abnormality signal based on the output of the detector, and a switching circuit connected between a pair of power source/signal lines. The apparatus further includes an oscillator and a control circuit which generates a signal for controlling the switching circuit obtained by the product of an output from the oscillator and the output of the signal processor. A power source is charged from the power source/signal lines, and supplies power to the detector, the signal processor and the oscillator.

Abstract: There is disclosed a smoke and/or heat detection apparatus including smoke and/or fire detectors, wire conductors embedded in a coextensive body of thermoplastic material and signal and actuating means.

Abstract: An alarm and control system for semiconductor factories or the like includes, at locations where poisonous and inflammable gases such as silane gas are used as in the manufacturing process of semiconductors, gas detectors to detect the leakage of the treatment gases and fire detectors to detect products of combustion of the treatment gases, and these detectors are adapted to cause, upon any changes in the output state of either of them, an alarm to issue and a protection device such as a fire distinguishing device as well as the manufacturing process to be controlled.

Abstract: Ionization of a medium being monitored is caused by an electric arc between a first pair of electrodes, while the conductivity of the medium between two measuring electrodes controls at least one feedback circuit which indicates relative rates of decay of the ions, as a function of variations in the number and mobility of ionized particles in the ambient medium.

Abstract: A smoke alarm mounted atop a Christmas tree, where an early indication of an impending fire may be generated. The alarm has built-in ionization chamber for smoke detection, control circuits for operating the ionization chamber and circuitry for processing and interpreting the output signals from the ionization chamber. In case of smoke detection, the control circuit operates a loudspeaker to generate a loud audible signal. The smoke alarm also has provisions for mounting atop a door. In an expanded version, the smoke alarm incorporates an intrusion alarm that is connected with a vibration detector with control circuits that operates the loudspeaker to produce a loud audible signal in case of tampering with the door. The alarm has provisions for self-checking the status of the built-in batteries and a light indicator shows if the batteries need replacement. A manual push button provides means for testing the smoke.

Abstract: This invention is a smoke or fire detector that first utilizes a signal that is indicative of a detected smoke or fire condition to operate an air moving device to purge the detectors photocell or ionization chamber and to thereafter allow an additional signal indicative of a detected smoke or fire condition within a predetermined time frame to provide an alarm signal. The smoke or fire detector avoids many false alarm situations by placing a cyclic purge switching control system between the smoke or fire detector and the alarm signal device. The cyclic purge switching control system sequentially connects the signal indicative of a detected smoke or fire condition between the air moving device such as a fan and the alarm signal device.

Abstract: A compact case houses a battery powered smoke detector, and an alarm clock is detachably mounted to the case. A mechanism is provided for releasably securing the case to the upper edge of a door, picture frame, or the like, so that the smoke detector is positioned close to the ceiling of a room where it more effectively detects fire. The detachable clock is removed and placed at a more convenient location apart from the smoke detector, for example, on a table in the room. A three-position switch is provided. In one position, the switch cuts off power to the smoke detector to prevent unwanted alarms. In another position, the switch causes an emergency light to turn on while the smoke detector is simultaneously deenergized. In the third position, the switch couples the light to the smoke detector circuit and engages this latter circuit such that the light automatically turns on when the smoke detector alarm sounds.

Abstract: A self test circuit for a combustion products detector automatically periodically tests whether the sensitivity of the sensor is in a predetermined range between minimum and maximum sensitivities. Transistor switches selectively connect different test impedances across the sensor for respectively simulating two amounts of combustion products, one of which is slightly less than the amount corresponding to the maximum sensitivity level and the other of which is slightly greater than the amount corresponding to the minimum sensitivity level. If the sensor either produces a smoke output signal in response to the first test or fails to produce an output signal in response to the second test, then the smoke alarm is actuated after the tests are completed to produce a unique fault signal, the alarm annunciator being inhibited during the test.

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

Abstract: A smoke alarm for responding to alarm conditions using electrical circuitry having a horn coil placed in series with rectifier circuitry. The series connection of the horn coil with the rectifier circuitry enables suppression of line transients and also eliminates the need for additional transient suppression circuits. An alarm condition causes generation of a short circuit which activates the horn and causes current to pass through the horn; but the high impedance of the horn coil in the rectifier circuit limits the amount of current drawn to low levels for more efficient and safe operation of the smoke alarm. Further, the current flow in the horn will be substantially AC as a result of the series connection of the horn and rectifier circuitry, thereby eliminating the need for an alternate reset current path.

Abstract: A central smoke detection system for a building having multiple rooms utilizes low cost commercial smoke detectors in each room. Each detector includes a steady high current alarm mode, a low current idle mode and a high pulse current test mode. A central power source supplies power to the detectors via one common lead and a separate power lead to each detector. A resistor in each power lead at the central location provides for monitoring of the mode of each smoke detector. A central monitor operates a visual smoke alarm responsive to the steady high current mode which indicates the room in which a detector is in the alarm mode and a visual fault alarm responsive to the absence of the high test pulse current indicating the room in which a detector is inoperative. A common central smoke and fault alarm, both audible and visual is also provided.

Abstract: A portable, battery powered smoke detector in which the operative components are compactly and efficiently arranged in such a manner that they may be housed in a pocket-sized casing approximating the shape and size of a cigarette package. A further embodiment shows an efficiently organized arrangement of the smoke detector components in a telephone set.

Abstract: An ionization detector of the type having a housing with electrodes and a radiation source for causing ion current flow between the electrodes, collector means for detecting, by a change in voltage, a drop in ion current flow, and means responsive to a predetermined change in collector voltage to provide an output signal, in which a test electrode is provided in the housing and means is provided for applying to the test electrode a predetermined voltage of a value that causes said predetermined change in voltage at the collector, whereby said output signal is provided when said predetermined voltage is applied to the test electrode if said detector is operating satisfactorily.

Abstract: An ionization type smoke detector (10) includes a chamber having a measuring electrode (12), the voltage on the measuring electrode being a function of the concentration of smoke in the chamber, and further includes a comparison device (A3) for comparing the voltage measured on electrode (12) at two different times, and an output device (K) for producing an output signal if the voltages differ by a predetermined value.

Abstract: A mounting bracket having multiple bayonet coupling elements which interengage with the bayonet coupling elements located on the body of an electrical instrument to be attached to a junction box. Additionally and in combination with the bayonet coupling elements, on the bracket and instrument body respectively, are included a pawl and ratchet arrangement for providing fine rotational adjustment while a toothed spring finger attached to the bracket engages a notched annular wall on the instrument body so as to latch and further secure the bracket to the body. It is anticipated that the mounting bracket will have to be attached to any one of several types of junction box thereby necessitating a multidirectional coupling arrangement for properly attaching the subject instrument to the particular junction box encountered.

Abstract: A single chamber ionization-type fire detector. The ionization current is directly amplified to provide a usable analogue signal by means of an operational amplifier which has a minimal effect in the ionization current. The operational amplifier is simultaneously employed to maintain a constant potential difference in the chamber so that the ionization current is not subjected to a fluctuating voltage. The amplified analogue signal drives a recorder and through analysis of the recorder output genuine fire alarm conditions can be distinguished from false alarm conditions.

Abstract: A self-calibrating obscuration smoke detector is provided along with a method for the operation thereof. A light source and a photodetector are mounted in spaced relation to one another with the output of the photodetector being a function of the amount of light sensed by the detector from the light source. The photodetector analog output is converted into digital signals by an A/D converter and digital signals are then delivered to a digital processor adapted to periodically calibrate the detector and to perform sampling operations between calibrations. Other sensing devices may be connected to the system with automatic self-calibrating capabilities with respect thereto including a temperature responsive element the output of which may be used to compensate for changes in ambient temperature.

Abstract: A fire alarm installation possessing increased intelligence which enables differentiating between smoldering fires and fires having open or licking flames. This capability is obtained in that the fire alarm installation possesses two sensor elements working according to different functional principles and an evaluation circuit contains circuit elements which form the quotient of the signals received from both sensor elements. The different sensor elements can be united in a single fire alarm housing which simultaneously contains the evaluation circuit.

Abstract: A smoke detector is incorporated into hand luggage for the traveler who must occupy high rise structures which may not have effective smoke detection equipment. Alternative power supplies minimize operating costs while insuring operation under all conditions.

Abstract: An ionization smoke detector device including means for insuring that adjustment can be made in the triggering potential for the alarm device so that should circumstances change, an operator can make a simple adjustment to take into account the changed circumstances. This means comprises a programmable Zener diode which is connected to a voltage dividing resistance network at the output of a field effect transistor, the other end of the Zener diode being connected to the input of a silicon controlled rectifier device which functions to trigger the alarm.Another primary feature of the present invention is the provision of a means for testing the operation of the system in such a way that all of the elements of the system will be tested rather than merely some of them.

Abstract: A combination optical and ionization detector for providing a more complete range of detection including detection of larger particles of combustion and smaller sub-micron particulates. Each detection channel (optical and ionization) may be independently calibrated and each has means such as an indicator light to identify which channel has alarmed. Each channel has detection circuitry for establishing both a pre-alarm condition and a full alarm condition. Differing alarm states are determined by the generation of audibly or visually distinguishable signals. For example a short signal may indicate a pre-alarm condition while a long, coded or modulated signal may indicate a full alarm condition. A further distinctive signal may indicate activation of two or more detectors. A supervisory channel may also be provided to detect, for example, circuit component failure.

Abstract: In a fire detection system having at least one fire sensor, a receiver including a power source connected to the fire sensor for supplying a power source voltage to the fire sensor and a receiving relay for receiving a fire detection signal from the fire sensor, and at least one power/signal line for coupling the fire sensor to the receiver, the receiver comprises a timer for producing a clock signal over the time of day and command means for providing predetermined detection sensitivity change commands of the fire sensor which are programmed according to the time of day in response to the clock signal from the timer, and the fire sensor comprises sensitivity change control means for changing the detection sensitivity of the fire sensor in response to the detection sensitivity change command from the command means. The fire detection sensitivity of the fire sensor is varied in accordance with predictive fire damage conditions predetermined in view of the activities of people during the time of day.

Abstract: The detector comprises a first electrode defined by a bolt mounted on an annular insulator which in turn is mounted on a printed circuit board and a second electrode defined by a cup shaped member which is aligned with the bolt and positioned with the interior thereof facing and being spaced from the bolt. A source of radiation is mounted on the head of the bolt and a third electrode is spaced outwardly from and laterally to one side of the head of the bolt. A box-shaped electrostatic shield is fixed to the printed circuit board and has an opening in which is positioned the cup shaped member. The shield serves to enclose the space between the rim of the cup shaped member and the printed circuit board. An annular insulator is mounted on and about the bolt.

Abstract: In an alarm installation containing a central evaluation unit and alarm devices arranged remotely therefrom, the transmission of energy from a radiation source and the reporting back of the signal occurs exclusively according to optical principles by means of radiation conducting elements, so-called light guides or conductors, by means of which the alarm devices are connected with the evaluation device. The alarm devices contain a preferably high-ohm sensor element, for instance a smoke-sensitive ionization chamber, whose operating voltage is infed by means of a solar cell which is irradiated by a light guide and whose output signal is fed back to the evaluation device by means of a high-ohm electrical transducer and a light guide. Such type alarm installation preferably is used for fire detection purposes, for gas, smoke temperature detection or intrusion protection, and is particularly suitable for use in an explosion-endangered environment or one subjected to electrical disturbances.

Abstract: A smoke detector having variable sensitivity to smoke levels and using one button both to test the smoke detector and actuate a mode of diminished sensitivity to smoke levels. The smoke detector is operable in a normal sensitivity mode and a diminished sensitivity mode with rapid switching between the modes. The sensitivity to smoke levels is substantially constant when in either the normal or diminished sensitivity mode.