Abstract: In a glass break detector, noise is removed by averaging the signal before it is analyzed for the characteristics that typically accompany glass breaking events. Low frequency signals, associated with glass flexing before it shatters, are isolated from repetitive or symmetrical noise in the same frequency range to increase the signal-to-noise ratio of the detector, improving sensitivity to valid glass breaking events and reducing false alarms.

Abstract: A personal security system includes signaling transmitters and receivers for detecting the transmitted signals. The receivers provide an output representing the received signal strength, which is used in combination with the position of the receiver for locating the point of transmission. All of the transmitters are substantially identical, at least in their transmission characteristics and transmitted signal strength, but include a first portable set of transmitters intended to be carried by subscribers, and a second fixed set of transmitters associated with the receivers. The fixed transmitters are actuated one after another and the receivers are polled to record received signal strength after each transmission from each receiver. The results permit comparisons with expected values, between receivers and over time.

Abstract: A smoke detector includes a dark chamber surrounded by a peripheral wall structure having a plurality of nested vanes. The second element of each vane is shorter than the first, and intersects the first element intermediate its ends at an acute angle. Adjacent vanes define a tortuous path that requires a minimum of three, and in most cases four, reflections for light to reach the inside of the chamber. Adjacent vanes define twisted channels leading from outside the chamber into the chamber for blocking light without substantially restricting the flow of air. The channels each include an outer section that extends in a direction toward the center of said chamber to define a channel entrance that admits airborne smoke with approximately equal resistance from opposite directions. The channels also define second and third sections that bend inwardly from the entrance toward said chamber, first in one direction and then sharply in another direction.

Abstract: A passive infrared motion detection system is provided with means for detecting increases and/or decreases in the sensor or system sensitivity by a predetermined amount vis-a-vis a nominal level. Various schemes are disclosed for implementing this concept.

Abstract: A multi-sensor security/fire alarm system comprises a master control unit which repeatedly interrogates, e.g., by a multiplexing scheme, the respective inputs and/or operating status of a plurality of remote sensor units (e.g., intrusion and fire sensors). In response to an alarm or other off-normal condition detected by any of the remote sensors, the master control notifies an alarm-monitoring service which either responds itself to the detected condition, or notifies the local police or fire department. To prevent one alarm-monitoring service from taking over, without authorization, the alarm-monitoring accounts of another service which may have expended considerable time and expense in installing the system, the master control unit is mated with its associated sensors by a unique code. According to a preferred embodiment, each sensor comprises an EEPROM which stores a unique portion (e.g.

Abstract: A security/fire alarm system includes a plurality of event-sensors, e.g. intrusion and smoke sensors, each being identifiable by a unique digital address defined by a multibit binary address code. A central control unit operates to repeatedly address the sensors to determine their respective alarm and/or operating status. To minimize the cycle time required to sequentially interrogate all sensors, the central control unit operates to address groups of sensors simultaneously, each of the groups consisting of a sub-plurality of all the sensors. In response to being addressed, each sensor in an addressed group of sensors transmits a different binary bit or digit of a multibit digital response code which is defined collectively by the transmitted bits. The logical state of each of such binary bits indicates the general status (i.e. normal/abnormal) of the event-sensing unit that transmitted the bit.

Abstract: A security apparatus having two control and communications units adapted to monitor a system and to establish communications over a connected telephone line and to transmit an alarm upon the occurance of a predetermined event in the system. The first control and communications unit produces a characteristic signal when it is operational; and the second control and communications unit is adapted to monitor the characteristic signal produced by the first control and communications unit and to establish communications over the connected telephone line and transmit an alarm upon interruption of the characteristic signal. The characteristic signal is preferably a tone of predetermined frequency.

Abstract: A microwave oscillator includes a metal housing which defines a cavity in which microwave radiation is produced by an internally mounted Gunn diode or the like. A tuning member projects into the microwave cavity through a hole formed in a wall of the oscillator housing. Depending on the length of its projection into the cavity, the tuning member controls the frequency of the microwave energy produced by the oscillator. The tuning member is supported on the cavity housing by a mounting member made from a material having a relatively high coefficient of thermal expansion. Particularly preferred materials include polymers such as polyethylene and polypropylene. Preferably, a microwave filter or choke is provided to reduce the leakage of microwave energy from the cavity through the hole in the oscillator housing. Such a choke comprises a pair of capacitors separated by an inductor.

Abstract: A personal security system includes at least one movable transmitter adapted to produce an emergency signal transmission when activated and a plurality of transceivers adapted to receive emergency signal transmissions from the movable transmitter. The received strength of an emergency signal received by one of the transceivers is compared with the received signal strength of an emergency signal received by other of the transceivers, and an alarm signal is produced by a transceiver in response to receipt of a transmission whose signal strength is stronger than any other transmission signal strength to which it has been compared. The alarm signal may include a code identifying both the activated movable transmitter and the transceiver producing the alarm signal.

Abstract: A personal security system includes at least one movable transmitter adapted to produce an emergency signal transmission when activated and a plurality of transceivers adapted to receive emergency signal transmissions from the movable transmitter. False alarms are avoided by inhibiting multiple transmissions by a movable transmitter within a predetermined time period.

Abstract: An intruder detection system includes a self-supervision feature which, on the basis of detecting authorized pedestrian traffic within a region under surveillance, alerts the system user of potentially faulty system components. Such system comprises a programmable timer which is repeatedly reset to a programmed maximum time interval by each occurence of an alarm-producing event, such as a disturbance of standing microwaves and/or a slight increase in ambient temperature in a region under surveillance. During "disarm" periods when the system alarm is intentionally deactivated to enable use of the protected region without the production of any alarm signals, each occurence of an alarm input to the system alarm (as produced by authorized traffic within the protected region) is used to repeatedly reset the timer to its preselected time interval (e.g., 1,4,8 or 16 days).

Abstract: A dual-tech intruder detection system includes a pair of intruder-detecting subsystems, each functioning to detect intrusion by a technology different from the other, and apparatus for activating an alarm in response to both subsystems detecting intrusion within a predetermined time interval. A supervisory circuit serves to detect a malfunction in one of the subsystems. Default apparatus, responsive to the output of the supervisory circuit, causes the alarm activating apparatus to activate an alarm in response to the still-functioning subsystem's detection of intrusion. To reduce false alarms from the still-functioning subsystem, circuit apparatus are provided for reducing the sensitivity of such subsystem in response to the output of the supervisory circuit.

Abstract: A multizone intruder detection system comprises a supervisory circuit for verifying, from normal traffic or activity in each of the zones of protection while the system is disarmed, that each of the intrusion sensors is, indeed, functional. In the event one or more sensors does not trip (i.e., sense activity) during the disarm period, the supervisory circuitry inhibits re-arming of the system until the non-tripped senso(s) is "walk-tested" to verify that it is still functional. According to the invention, a programmable timer enables re=arming of the system for a predetermined (preferably brief) time interval immediately following disarmig of the system. This feature offers the edvantage of allowing the user to re-enter the protected premises "after hours" for a brief period of time without having to walk-test all zones of protection before re-arming the system.

Abstract: An autodyne microwave motion-detection system includes a supervisory circuit for monitoring the operating status of the microwave energy-producing component of the system. According to a preferred embodiment, the supervisory circuit of the invention comprises a relatively low-cost, "general purpose UHF" diode, i.e. a multipurpose diode commonly used in circuits designed to accommodate UHF frequencies of up to only about 3 Gigahertz. The supervisory diode is positioned within, or in close proximity to, the resonant cavity of the microwave energy-producing element, the latter being designed to produce microwave energy at a substantially higher frequency (e.g., 10.5 Gigahertz). Due to its close proximity to the microwave energy-producing element (e.g. a Gunn diode) and its presence within the energy field produced thereby, the supervisory diode develops a small, but readily detectable, voltage whenever such element is radiating microwave energy.

Abstract: A dual channel intrusion detection system comprising first and second radiation sensors. Each sensor has a pair of elements viewing adjacent zones of the protected area, the zones being slightly offset from each other in the direction of expected intruder movement. Sequence detection is provided for producing an intruder-present signal in response to simultaneous actuation of one element of each sensor when preceded by actuation of the other element of one of the sensors. Additional immunity from false triggering is obtainable if this sequence must be followed by actuation of the other element of the second sensor.