Abstract: A plastic cover covers a surface-mounted junction box which delivers wires to an alarm unit or emergency light or the like which is mounted to the cover. The cover is connected to the junction box by screws which engage threaded holes provided by the junction box. The cover can be mounted to either a single wide junction box or a double wide junction box and provides corresponding holes for connection to either box. The alarm devices can be connected to the cover directly by screws or by a combination of a single screw and a tab which is received into a slot on the cover. The cover and alarm unit together form an architecturally attractive cover for an otherwise industrial appearing junction box. When the cover is attached to the junction box, the box no longer can be seen. The covers can be color coded for a particular alarm service, such as fire, weather warnings, or other emergency conditions.

Abstract: Circuits for supervising message generators and audio output cables include memory for binary storage of messages previously recorded in a message generator. As the generator is cycled to produce an audio output, that analog output is sampled and compared to the previously stored binary representation. A match indicates a successful generation of the message. The cables can be supervised by applying a DC bias thereto and detecting the voltage present on the respective cable. Line integrity is indicated where the cable DC voltage falls in an expected range.

Abstract: A detector tamper/trouble delay circuit incorporates a sensor which senses the presence or absence of a cover for the detector. When the cover is removed, the sensor triggers a delay element preset for predetermined time interval. If the cover is replaced during the time interval, no trouble or fault indicator is generated. If the cover remains off the detector for the entire time interval, a trouble or fault indicator will be generated. The indicator can be used by an alarm system control element or a stand alone trouble or fault indicator for producing a humanly perceptible representation of the existence of the fault or trouble condition.

Abstract: A very low profile ionization chamber provides increased operating current by using alpha particle emitting isotopes having low emission energies as an ionization source. The chamber includes a cylindrically shaped housing having height generally equal to a radius thereof. A conically shaped sensing electrode is carried within the housing. The housing is closed at one end by a main field electrode and at the other end by an insulating closure panel. A second field electrode is carried on the closure panel. The second field electrode also carries the ionization source. The conically shaped sensing electrode has an open central region which permits alpha particles to travel therethrough toward the first field electrode. The first field electrode could either exhibit a conical cross-section or could be planar. A chamber height on the order of 1.5 to 2 centimeters and a diameter in a range of 3-4 centimeters with a Gd148 source produces operating currents on the order of 10 pA.

Abstract: A pulse detection circuit to be used in combination with a generator of a train of synchronizing pulses. The detection circuitry remains in a first, inactive state in the presence of an ongoing sequence of synchronization pulses. In the event of a detected absence of synchronizing pulses for a predetermined period of time, the detection circuitry changes state and generates an electrical output signal indicative of one or more missing synchronizing pulses. The detection circuitry can incorporate either digital or analog timing circuitry.

Abstract: An adjustable sampling tube construction for a duct-mounted smoke detector includes telescopic tube sections which can be fixed in overall length by a screw extending through an outer tube to fix an inner tube with respect to the outer tube. The inner tube includes air sampling holes spaced apart along its length and the outer tube includes a plurality of spaced apart through holes having a same spacing to register with the sampling holes of the inner tube. The inner tube is telescopically positionable within the outer tube to register the sampling holes with the through holes to provide air sampling locations throughout a length of the combined inner and outer tube assembly.

Abstract: An AC load switching system predicts when a zero voltage cross-over condition will exist for purposes of switching an AC load to minimize inrush currents. Prediction is carried out by characterizing the switching devices, which preferably are electromechanical in nature, and determining closure and bounce delays associated with each type of switching device. The system includes a processor, which could be a programmed microprocessor. The processor stores characterization parameters for the load switching elements including closure delay time as well as bounce time intervals. The processor energizes a switching element to close same at a time during the AC line cycle such that when the delay interval has passed and one half of the bounce interval has passed, the line voltage will be at a cross-over or zero voltage condition thereby resulting in minimal inrush current when the contacts have completely closed.

Abstract: A system and a method for dynamically adjusting a level of filtering or smoothing applied to data received from fire detectors produces shortened response times for detection of a fire condition while at the same time minimizing the effects of uncorrelated noise in the absence of any fire condition. An increasing probability of a fire results in less filtering. Increasing values of the input signal from a respective detector, indicative of an increasing selected ambient condition such as combustion or temperature, provide a control input for reducing or bypassing the level of filtering of the respective input signal thereby reducing system response time. Where the unfiltered input data from a respective detector indicates a combustion or temperature profile moving toward clear air, the filtering or smoothing level can also be dynamically decreased thereby enabling the filtered signal values to return to their respective clear air values faster than would otherwise be the case.

Abstract: A self-testing data communications system suitable for use with an alarm system, the communications system being capable of modifying an operational parameter such as the input signal sensitivity of a receiver located at a monitoring station during receipt of a supervision signal from a remote alarm device, in order to ensure that a non-supervision alarm signal will be properly received when the operational parameter is again returned to its normal state.

Abstract: A unique wireless transmission signal structure has a preamble at a first data rate and a data portion including the base band signal at a second, higher data rate. The signal is generated in a manner which ensures that the transmitted signal is "on" no more than one half the entire transmission time. A unique wireless transmitter generates the inventive transmission signal. A crystal oscillator drives both a signal generation circuit and a frequency generator. This provides accurate timing and allows the transmission signal to be not self-clocked. A unique wireless transmission receiver has adjustable pre-detection and post-detection filters. When the receiver is scanning for an incoming transmission signal, the pre-detection filter has a wide bandwidth to receive incoming transmission signals within a predictable range of variations due to inaccuracies in the transmitter and receiver. At this time, the post-detection filter has a narrow bandwidth to pass the low bit rate preamble data and reject noise.

Abstract: A self testing wireless data communications system suitable for use with an alarm system, the receiving element of the communications system is capable of measuring the signal strength (RSSI) of the received message signal and comparing it, if it is a supervision message, to a predetermined threshold value. When the supervision RSSI signal is above the threshold, the received message is passed to the control as being validly received; when the supervision RSSI signal is not above the threshold, then the message is ignored.

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 self testing wireless data communications system suitable for use with an alarm system, the receiving element of the communications system is capable of receiving the message simultaneously at two different sensitivity levels, and during a supervision message, the lower sensitivity path is used in order to ensure that non-supervision alarm messages are received with an adequate signal margin.

Abstract: An apparatus and a method can be used to pre-process an output signal from an ambient condition sensor. The preprocessing removes noise pulses which are not correlated with an ambient condition being sensed. Preprocessing can be carried out by comparing the present output value to a prior output value and selecting a minimum value there between. The apparatus and method can incorporate storage for two prior values and the present output value can be compared to two prior values and a minimum or a maximum of the three values selected. Additional processing can be carried out by comparing the present output value to a nominal expected clear air output value. If the present value exceeds the nominal expected output value, a minimum is selected among the present output value and one or more prior values. If the present output value is less than the nominally expected value, a maximum is selected from among the present output value and one or more prior output values.

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: Outputs from a smoke detector and non-fire sensors such as temperature and humidity can be combined to produce a delay in a signal from the smoke sensor indicative of a potential fire condition. The signals can be combined locally and all of the sensors can be carried in a single housing. Alternately, the sensors can be carried in separate housings and combined at a remote control panel. The value output from the humidity and temperature sensor can be used in determining whether or not to produce a delay. Alternately, the rate of change of either or both parameters can be used to determine whether a delay is necessary.