Abstract: A wireless alarm system (10) employs two-way transceivers (32, 60) in a network of smoke detectors (16), a base station (12), and other sensors. A keypad (14) is not needed because the system is reset by pressing a Test/Silence button (66) built into every detector or sensor. A siren is also eliminated because a sounder (64) in every detector sounds an alarm when any sensor is triggered. This is possible because every detector includes a transceiver that can receive alarm messages from any other detector. AC power wiring is also eliminated because the base station and sensors are battery powered. Only a telephone connection (48) is needed if the system is to be monitored. In apartments or dormitory installations, smoke detectors in one apartment relay alarm messages to the next apartment, and onto the next, and so on, to a centralized base station for the entire facility.

Abstract: An electric power line communication system operates with an electric power distribution system to provide through premises power distribution lines highly reliable communication links among receiving devices electrically coupled or located in proximity to the premises power distribution lines. A power line transceiver is designed to transmit and receive through the premises power distribution lines modulated carrier signals conveying information over the communication links. The power line transceiver operates in a transmitter mode as an intentional radiator to emit modulated carrier signals by transmitting them at a frequency band and a power level sufficient to form by electrical conduction a communication link with a modulated carrier signal receiving device.

Abstract: An electric power line communication system operates with an electric power distribution system to provide through premises power distribution lines highly reliable communication links among receiving devices electrically coupled or located in proximity to the premises power distribution lines. A power line transceiver is designed to transmit and receive through the premises power distribution lines modulated carrier signals conveying information over the communication links. The power line transceiver operates in a transmitter mode as an intentional radiator to emit modulated carrier signals by transmitting them at a frequency band and a power level sufficient to form by electrical conduction a communication link with a modulated carrier signal receiving device.

Abstract: A fire detection system combines a CO.sub.2 gas detector with a smoke detector. Logic circuitry combines the outputs of both detectors to minimize false alarms and provide a rapid response time. In a preferred embodiment the need for periodic cleaning is reduced. In a further preferred embodiment, two alarms indicative of two different types of fires, for example flaming fires and nonflaming fires are available. A map of flaming fire and smoke may be assembled by the system to guide the firefighters. In a yet another preferred embodiment, a tentative fire alarm indication disables a local air conditioning system thereby helping to isolate and control any existing fire.

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: An intelligent switching mechanism for the backup batteries of an alarm system is disclosed. When AC input power has failed but no alarm has been declared, the batteries are switched into a parallel configuration, which is sufficient to supply the control panel, so that the batteries are drained in tandem. When AC input power has failed and an alarm has been declared, the batteries are switched into a series configuration to supply power at the higher voltage required by the alarm annunciators.

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: 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: An improved environmental alarm system has centralized control of local sensor display capabilities displays, on the sensor itself, a variety of sensor data including sensor address, and detected levels of one or more environmental conditions. Alphanumeric characters are displayed at individual sensors in response to commands from a master microprocessor directing local sensor display content and timing. A local microcontroller within each sensor interprets the detected signal and prepares a resulting data signal that is available for downloading into the alphanumeric display in compliance with a coded message from the master microprocessor.

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: Fresnel lens elements in a lens grouping and mounted in a fixed relationship to a detector, to define a 360.degree. field of view for use in a sensor for passive detection of infrared radiation. Lens elements of the lens grouping can be selected by masking other lens elements, to leave a lens array defining a particular pattern of detection for a desired application. By masking certain of the lenses of the lens grouping, wide angle three-dimensional or fan-like planar curtain patterns of detection are obtained for use of the sensor in either a wall-mounted or ceiling-mounted installation, and vertical curtains of coverage can be obtained using ceiling-mounted installation. Lens elements of different sizes and focal lengths are arranged to gather ample radiation for detection of distant intruders in certain directions.

Abstract: Apparatus and a method for previewing the field of coverage of an infrared sensor and, accordingly, adjusting its position for use in an intrusion detection alarm system. A mirror can be mounted in place of the infrared sensor and has indicia corresponding to beams of sensitivity of the infrared sensor to provide an indication of the beams of sensitivity superimposed on an image reflected by the mirror to aid in adjusting the position of the infrared sensor. Alternatively, or as verification of the sensor position, a photograph can be prepared by use of a camera located in a proposed infrared sensor position. Directional beams of sensitivity of the infrared sensor are plotted on the photograph by the use of a prepared transparent overlay showing the correspondence between areas of the photograph and respective elements of the lens of the infrared sensor. Portions of the sensor lens are masked to block reception of infrared radiation from known sources along beams of sensitivity of the infrared sensor.

Abstract: A glass break defection system includes a unidirectional acoustic transducer directed toward an area of glass to be monitored. The transducer is narrowband and has a sharp frequency response peak in the 4 to 8 kHz range. An electronic audio discriminator connected to the transducer output is responsive to signals within this frequency range having a predetermined amplitude thereby eliminating ambient or environmental sounds not characteristic of breaking glass. The transducer is mounted in a rectangular enclosure which is pointed at the area to be monitored and comprises a flat circular metallic disk affixed to the enclosure with a piezo electric element affixed to the rear of the metallic disk. The enclosure is tuned to resonate at a frequency characteristic of the sound of breaking glass.

Abstract: A self-powered sensor for a closed-loop security system includes a self-powered sensor network which provides a switch-actuating signal upon the detection of a physical condition. An electronic switch, which is in a normally closed position, is connected between the positive and negative poles of a closed-loop security system and opens the loop upon receipt of the switch-actuating signal thereby triggering an alarm. The self-powered sensor network may include a voltage doubler for converting the AC output of a transducer to a DC voltage of an amplitude sufficient to open the switch. When the switch is opened, voltage from the closed-loop security system becomes available to power a visible or audible alarm identifying the sensor that opened the loop.

Abstract: A self-powered sensor for a closed-loop security system includes a self-powered sensor network which provides a switch-actuating signal upon the detection of a physical condition. An electronic switch, which is in a normally closed position, is connected between the positive and negative poles of a closed-loop security system and opens the loop upon receipt of the switch-actuating signal thereby triggering an alarm. The self-powered sensor network may include a voltage doubler for converting the AC output of a transducer to a DC voltage of an amplitude sufficient to open the switch. When the switch is opened, voltage from the closed-loop security system becomes available to power a visible or audible alarm identifying the sensor that opened the loop.