Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2002-09-04
2004-10-19
Wu, Daniel J. (Department: 2636)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S552000, C340S555000, C340S556000, C340S557000, C340S564000, C250S221000
Reexamination Certificate
active
06806811
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
SEQUENCE LISTING
Not Applicable
BACKGROUND
1. Field of Invention
This invention relates to alarm systems, and more particularly to a perimeter monitoring system which uses infrared links to create a boundary through which intrusion is detected.
Still more particularly, the infrared links of the perimeter monitoring system may optionally be synchronized so that the infrared transmitter for one link will not falsely be received by the receiver of another link and, optionally, breach information can be transmitted to a base location.
2. Description of Prior Art
Personal and property security has long been a concern and continues to be as evidenced by increased utilization of automobile and house alarms systems. The most prevalent type of alarm is that of intrusion detection, where incursion into some defined area is sensed and indicated with either an overt broadcast alarm, or a covert alert, e.g., an automatic telephone call to the police. A example of this is a simple automobile alarm which is triggered by the opening of doors (the existing door button that activates the internal dome light is often used). In this case access to the protected area, the internal space of the car, is generally made at specific locations, i.e., the car doors, and only these are sensed. (Of course, more sophisticated car alarms may include motion sensors so that window entry is also detected). Another example of existing intrusion detection systems are the many house alarm systems available. Here the detection methods can be separated into two general categories: 1) internal presence detection, and 2) perimeter violation. Examples of the former are proximity motion and heat sensors. In the latter case, as in the car alarm, advantage is taken of the fact that entry is generally made via specific locations, e.g., windows and doors, and sensors are thus placed at those points. Internal presence detection via proximity detectors can be very effective but have two drawbacks: they can be tripped unwontedly by pets, and by their very nature only alarm after premises entry has already been made. A perimeter security system consisting of a series of door and window sensors, on the other hand, although often times more difficult to install, can provide secure protection along with free internal movement. Of course, many home protection systems include both categories for optimum security.
Another example of perimeter violation protection, and one that encompasses a larger area, is estate property that is bordered by an entry-resistant wall. Here, again like the car alarm and the house perimeter sensors, entry is limited to specific locations, in this case the driveway, and an intrusion sensor is placed only there. Unlike the perimeter sensors used in a house system that need only detect, for example, that a window or door contact has been broken, however, the sensor method used here must detect an intrusion through a span of open area, e.g., the driveway opening in the wall. A point-to-point infrared transmitter/receiver pair can serve this purpose and U.S. Pat. No. 3,370,285 describes one such system. Here, an infrared beam is established between a transmitter and receiver placed at either end of the span to be protected. Cessation of the beam reception by the receiver caused by, for example, an intruder constitutes an area violation.
The Tandy Corp., via their Radio Shack line of stores, offers a similar system, however here the transmitter and receiver are contained in a single unit which could be placed at one side of the protected span, while an infrared reflector is placed at the other end, so that the beam travels twice across the span before being detected by the receiver. The operational effect is the same as U.S. Pat. No. 3,370,285, however, the Tandy system has the advantage in that all of the electronics, and thus the powering requirements, are contained in a single unit.
Another point-to-point light beam alarm application is described in U.S. Pat. No. 4,998,093. Here a light beam emitter and separate photoelectric detector are used to protect road workers by detecting when errant vehicles have crossed into the road work area. When the light beam is broken circuitry associated with the photoelectric detector transmits radio frequency warnings to radio receivers worn by each worker in order to communicate a potential danger alert.
A more difficult alarm protection situation occurs when an open area needs to be secured. In the estate example above, for example, if no effective deterrent wall exists, then the single point-to-point detection scheme is inadequate since instead of a short open span to protect, now an entire perimeter must be secured. Other examples of open areas that would be desirable to protect would be for campers in remote areas, or small children in play areas (here the need would be to contain the children within the area, rather than alarm against intrusion from without). A common approach is to use a series of proximity sensors to create a detectable perimeter. U.S. Pat. No. 6,118,375, for example, describes a portable proximity sensing apparatus that could be used as a component in such a system. Here multiple of these devices are placed so as to create a perimeter around the protected area whereby each can sense motion within a circle in its proximity, and the devices are placed so that the series of resulting protected circles overlap and create a complete secure perimeter. Motion above some threshold causes the detecting device to generate a warning by audible alarm, flashing lights, or a combination of the two. The great disadvantages of this type of system are three-fold: firstly, in open areas outdoors proximity sensors are easily susceptible to false triggering due to wild or tame animals, or due to wind causing movement of buses and tree branches; secondly, the very nature of proximity sensing reduces the perimeter usable area since the zone of detection is defined by the inner limit of each detectors range (and additionally disadvantageous since it is difficult for the users to know precisely where this boundary is); and thirdly, the alarm method—audible or visual warnings—would serve to warn an intruder as effectively as the user.
More precisely defined perimeter protection methods have been proposed using wires. U.S. Pat. No. 4,091,367 describes the use of parallel-placed leaky coaxial cables to detect movement of human-sized objects past them via perturbations of RF signals continuously propagated around the cables. Alarming is provided at a base location where RF transmission and reception occur, and can take various forms, including methods that would be undetected by an intruder. Although this scheme solves the proximity detection problems of an ill-defined perimeter and warnings made to the intruder as well as to the user, since it is based on threshold detection of RF energies it remains to some degree susceptible to either false triggering on one hand, or undetected intrusions at the other. Additionally, this scheme could be cumbersome to deploy in remote, temporary situations, such as a camp area.
Another method of precisely defining a secure perimeter involves using a series of point-to-point light beam span protections. U.S. Pat. No. 4,978,942 describes one such system using infrared transmitters and receivers that are enclosed in containers camouflaged to appear as ordinary industrial storage drums. The patent disclosure describes that these units could be placed in series, presumably such that the transmitter of each is associated with the receiver of the next device in the perimeter. Warnings of intrusion are sent via radio frequencies to some base location for alarming. Although this scheme also solves both the problems of the ill-defined perimeter and warnings made to the intruder, it includes the undesirable complexity of radio links which themselves can be prone to unreliability due to natural and manmade interference.
Finally, U.S. Pat. No. 4,998,093 mentioned earlier describes the use of a r
Pham Lam
Wu Daniel J.
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