Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-02-26
2001-10-23
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S552000, C340S554000, C340S567000, C340S522000, C340S506000, C340S539230
Reexamination Certificate
active
06307475
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to alarm and warning systems, and is particularly concerned with a system and method for detecting and tracking movement within an enclosed space such as a building.
Conventional building alarm systems have the primary purpose of detecting an intruder and warning the owner or security agency of the presence of the intruder. These traditional systems simply look for an abnormal event and activate a warning device or transmit a warning signal to a remote station. The alarm system does not normally continue to check or monitor the space when already in the alarm state. These alarm systems are normally installed on the inside of buildings to protect the building or structure from intrusion.
One such conventional alarm system is described in U.S. Pat. No. 5,150,099 of Lineau, which describes a home security system for detecting stationary and moving objects within an area. The system transmits electromagnetic radiation into the monitored space, and senses the amplitude of radiation reflected or refracted off objects in the space. The information generated is compared with a pre-generated template, and the device produces an alarm condition if any variations are found. This system does not have any ability to track movement within a monitored space, but simply generates an alarm when a body not in the pre-generated template is detected.
U.S. Pat. No. 5,786,760 of Suzuki et al. describes an alarm system for both detecting the presence of an intruder, and for deterring the intruder by producing a variable, audible alarm or warning signal. The system utilizes plural transmitters of electromagnetic radiation located outside a building but within a fenced area. The radar system detects and monitors the position of an intruder within the outdoor fenced area, and outputs synthesized human or dog voice sounds at varying levels towards the intruder, so that it appears that the intruder is being approached. This system also does not provide any means for monitoring intruder position within an enclosed space.
U.S. Pat. No. 5,448,501 of Hablov et al. describes a detection system for building surveillance which uses a microwave transmitting/receiving device for radiating microwaves into an area and detecting and conditioning the reflected signal received as a result of individuals within the area. The system includes a method of identifying individuals within a building in order to distinguish authorized persons from unauthorized persons, but does not provide any means for tracking movements of intruders within a building.
Although current building alarm systems mounted within buildings can effectively detect a break-in or the like, they are of little or no help to law enforcement officers arriving on the scene where it is suspected that an intruder is still within the building. They are also of no help in situations where a gunman has barricaded himself within a building, with or without hostages. Therefore, there is a need for a system which would locate and monitor a living being from the exterior of a structure or building and track any movement of that being from region to region within the structure. This system would be particularly useful for police officers or SWAT teams in situations where a gunman has barricaded himself within a building, in some cases with hostages. Currently, officers are not able to determine the exact location of the suspect or suspects in the building, or monitor movement in the building. Internal surveillance cameras may not be present and, even if present, can be disabled by the suspect quite easily. An ability to locate the exact position of the or each suspect in such situations can considerably reduce the risk to both hostages and police officers when officers enter the building.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and improved method and system for detecting and tracking movement within a building or enclosed space.
According to one aspect of the present invention, a system for detecting and tracking movement within a building is provided, which comprises a plurality of portable electromagnetic radiation transmitter and detector units for deploying outside the walls of a building to be monitored, each unit having an transmitter for transmitting electromagnetic radiation through the building walls into a monitored area, a receiver for detecting radiation reflected back to the unit from the monitored area, and an output device for transmitting an alarm signal from the unit if a shift is detected in the reflected microwave energy, indicating movement within the area, and a receiver unit for receiving alarm signals from each of the transmitter/detector units and producing an output signal for each transmitter/detector unit currently detecting movement to provide the user with information on the location of any movement within the building.
In a preferred embodiment of the invention, the receiver unit has a plurality of alarm indicator lights such as LEDs on a front panel, each LED corresponding to a respective transmitter/detector unit. Law enforcement officers can deploy the transmitter/detector units around the building, and then monitor the receiver unit to detect which monitored space or room currently has movement, and can also monitor movement from room to room as LED lights go on and off.
The transmitter and detector in each transmitter/detector unit is preferably a Doppler microwave transmitter and detector placed in a housing which has all walls apart from a front window formed from a radar absorbing material to attenuate any microwave energy emanating out of or into the housing via the side and rear walls. This avoids any false indication of movement as a result of movement near the sides and rear of the unit, for example movement of officers deploying the unit outside the building. This arrangement allows the unit to be deployed in a hand-held mode, although transmitter/detector units may also be mounted on support stands or tripods for standing adjacent building walls.
This system takes advantage of the characteristic of microwave radiation to penetrate solid structures, and to reflect from objects back to its origin. If a frequency shift is detected in the microwave energy received at the detector, this indicates movement within the monitored area. In a preferred embodiment of the invention, at least two different types of transmitter/detector units are provided. A first, basic unit comprises a microwave transmitter and detector, and a relay unit or transmitter connected to the detector output. The second transmitter/detector unit has an encoder device and a radio transmitter, and is connected by hardwiring or radio to each of the first, basic units to receive the outputs from those units. The second type of transmitter/detector unit is set up to encode alarm signals from its own microwave receiver/detector, as well as alarm signals received from the first units to which it is connected on different channels, and provides an output data stream which is transmitted by the radio transmitter to the receiver unit, which decodes the data stream to determine which of the first and second units is currently detecting movement. This arrangement allows multiple detectors to send signals over a single radio frequency from a single transmitter. The number of first units which can be connected to a second transmitter/detector unit is dependent on the number of channels available on the encoder, minus one channel for the channel occupied by the detector unit of the second unit itself. If the second unit has an
8
channel encoder, eight different encoded signals can be transmitted over the same radio frequency, from up to seven attached basic units and the second or encoder unit itself.
According to another aspect of the present invention, a method of monitoring an enclosed space and tracking movement within the space is provided, which comprises the steps of:
placing a plurality of transmitter/detector units around the outside of the space to be
Brown Martin Haller & McClain LLP
Hofsass Jeffery
Nguyen Hung
LandOfFree
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