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: 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 moisture detector for detecting the presence of moisture between two electrodes includes an AC sensing network coupled to an indicator circuit by an opto-isolator to isolate impedances between the two circuits. The battery life of the detector is extending by a unique pulsing technique that creates current drain in the sensing circuit for only brief intervals of time. The pulsing technique enables the indicator circuit to keep an electronic switch in a closed-loop security system in an on state.

Abstract: Apparatus and method for communication by use of a single FM radio frequency, from a plurality of transmitters to a central receiver in a security alarm system or similar system. A transmitter's radio frequency signal is modulated in wide frequency swings to transmit digitally encoded address, subaddress, and sensor status information in a very brief format. The receiver automatically tracks the rapidly varying frequency of the transmitted signal. A transmission is provided periodically from each transmitter, but a very low duty cycle is used to avoid interference among the transmitters. Address and subaddress data identify each transmission and a maintenance warning is provided by the receiver-decoder unit to identify any transmitter which fails to report within a predetermined time. Each significant sensor change initiates a transmission from the related transmitter. Low duty cycle and low transmitter power requirements provide long transmitter battery life.

Abstract: Apparatus and method for communication by use of a single FM radio frequency, from a plurality of transmitters to a central receiver in a security alarm system or similar system. A transmitter's radio frequency signal is modulated in wide frequency swings to transmit digitally encoded address, subaddress, and sensor status information in a very brief format. A transmission is provided periodically from each transmitter, but a very low duty cycle is used to avoid interference among the transmitters. A transmitter frequency sweep provides the receiver an opportunity to lock onto a transmission before data is transmitted. Thereafter the receiver automatically tracks the rapidly varying frequency of the transmitted signal. Address and subaddress data identify each transmission and a maintenance warning ir provided by the receiver-decoder unit to identify any transmitter which fails to report within a predetermined time. Each significant sensor status change initiates a transmission from the related transmitter.

Abstract: A housing for an elongate electronic circuit board, including longitudinally extending support rails and opposing pins within the housing to support the margins of a portion of the electronic circuit board which is not deformation-sensitive. A recess is provided on the exterior of the housing to hold electrical power cells therein, thus separating them from the circuit board. An opening to the interior portion of the housing provides access to a portion of the circuit board.

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.