Abstract:
An object that can be sensed by a motion detector is equipped with a small, battery powered transponder. A motion detector has (either internally or externally) a transceiver adapted to provide a query signal. If the object is within range of the query signal, the transponder responds with a transponder signal. The transceiver is responsive to receipt of the transponder signal to prevent the detection of motion from causing an alarm.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to security systems and particularly to motion detectors for security systems, such as passive infrared (IR) detectors. 
     BACKGROUND OF THE INVENTION 
     Motion detectors for security systems are well known. The most common type of motion detector is a passive IR detector that detects motion from animate, moving objects that that emit IR, such as humans and animals. (The term “objects” as used herein includes animals and humans.) 
     Animals, and especially cats, pose special problems for environments employing security systems with motion detectors because they are usually free to roam spaces in which motion detectors are employed (“protected space”) and hence, when the security system has been armed, they can set off an alarm when they enter the protected space. Although the protected spaces are usually zoned and specific zones can usually be bypassed, this defeats the purpose of installing the motion detector in the protected space in the first instance. 
     Humans also pose a problem because they might forget that the protected space has been armed with a motion detector and wonder into it. Again, though protected spaces can usually be bypassed, bypassing defeats the purpose of the alarm system, and also humans can forget to bypass the protected zones when they arm the system. 
     It is desirable to provide a means by which protected spaces can remain armed and protected by motion detectors, but which allows authorized objects to roam within those spaces without setting off the alarm. The present invention achieves this goal. 
     SUMMARY OF THE INVENTION 
     An object that can be sensed by a motion detector is equipped with a small, battery powered transponder. A motion detector has (either internally or externally) a transceiver adapted to provide a query signal. If the object is within range of the query signal, the transponder responds with a transponder signal. The transceiver is responsive to receipt of the transponder signal to prevent the detection of motion from causing an alarm. 
    
    
     DETAILED DESCRIPTION OF THE FIGURES 
     FIG. 1 is a block diagram illustrating a motion detector according to one embodiment of the present invention. 
     FIG. 2 is a block diagram illustrating a motion detector and an adapter therefore according to another embodiment of the present invention. 
     FIG. 3 is a block diagram illustrating a wireless motion detector according to one embodiment of the present invention. 
     FIG. 4 is a block diagram illustrating a wireless motion detector and an adapter therefore according to another embodiment of the present invention. 
     FIG. 5 is a flow diagram illustrating the operation of the devices of FIGS. 1-4 according to one method of the invention. 
     FIG. 6 is a flow diagram illustrating the operation of the devices of FIGS. 1-4 according to another method of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is described herein in the context of the presently preferred embodiments, but is not limited thereto except as set forth in the appended claims. 
     Referring to FIG. 1, there is shown a motion detector  10  having a motion sensor circuit  12  therein in well known fashion. Motion detector  10  may be a commercially available passive IR motion detector, such as the model DS774Ti (www.detectionsys.com) or DS820I manufactured by Detection Systems Inc., Fairport, N.Y. As is well known, many motion detectors  10  operate using 4 wires, two of which deliver DC power to the device, and the other two of which report status to an alarm panel (e.g., relay contact closure upon detection of motion). Wireless passive IR detectors are also known, and an embodiment of the present invention is described herein in connection with such wireless devices. As is known, the motion detector communicates with an alarm panel that sounds an alarm if motion detector  10  reports a breach indication (motion) over the status lines  22  (or wirelessly). 
     Motion detector  10  is equipped with a transceiver  14  that cooperates with a compact, battery powered transponder  16 . Examples of such transceivers  14  and transponders  16 , and systems suitable for the present invention, are described in U.S. Pat. Nos. 5,351,052; 5,453,747 and 5,053,774, and also in U.S. Pat. Nos. 6,236,314; 6,026,868 and 5,605,182, all of which are incorporated herein by reference. Commercial implementations of such devices can be found in so-called “Easy Pass” traffic/toll systems and in the Mobil Speed Pass system promoted by Mobil Oil Corporation (www.speedpass.com). As is well known in such systems, transponder  16  transmits on a unique frequency and/or using a unique code (“transponder signal”) in response to a query signal from transceiver  14 . Motion detector  10  is also equipped with logic circuitry  18 , such as digital or analog logic circuitry. According to the invention, a transponder  16  is placed or worn on an object  20  that may enter the protected space. According to one embodiment of the invention, transceiver  14  transmits a query signal only in response to an indication of motion from the motion sensor circuitry  12  (shown on line  21 ). If the transponder replies with a transponder signal, then logic circuitry  18  prevents the breach indication, that would normally cause the alarm panel to generate an alarm, from doing so, e.g., by preventing the breach indication from being sent to the alarm panel over status lines  22 . See FIG.  5 . Otherwise, the breach indication is provided to the alarm panel. It may be desirable to adjust the transceiver  14  and transponder  16  so that their effective transmission/reception reception ranges are no greater than the detection range of motion detector  10  and/or of the area of the protected space. 
     In alternative embodiments, transceiver  14  transmits query signals at periodic intervals, or transmits query signals constantly, rather than in response to an indication of motion. See FIG.  6 . 
     FIG. 2 illustrates an embodiment of the invention which does not require modification of a commercially available motion detector  10 ′. In this embodiment, the invention is provided as an adapter or retrofit device  15  that can be externally connected to the motion detector  10 ′. Particularly, the transceiver  14 ′ and logic circuitry  18 ′ receive the status lines  22  (and DC power) externally to the motion detector  10 ′. This can be accomplished by a simple plug and receptacle arrangement, shown by the circles  24 . The transceiver  14 ′ and logic circuitry  18 ′ may be contained in the same or separate housings. The operation is as described above. 
     FIG. 3 illustrates a commercially available wireless motion detector  10 ″ that, instead of employing status lines  22 , has a built in (or external) radio transmitter  26  that is tuned to transmit a breach indication at frequency f 1  in response to the detection of motion. Receiver  28  at the alarm panel  30  is likewise tuned to receive at frequency f 1 . If receiver  28  receives a transmitted breach indication, the alarm panel  30  sounds an alarm. (As is known, the transmitted breach indications may be coded for indication of the zone in which the breach occurred.) As in the embodiment of FIG. 1, the motion detector  10 ′ is modified to incorporate a transceiver  14 ″ for communicating with a transponder  16 , and logic circuitry  18 ″. Logic circuitry  18 ″ prevents the transmitter  26  from transmitting a breach indication to the receiver  28  if, as indicated in FIGS. 5 and 6, a transponder signal is received in response to a query signal. Otherwise, the breach indication is transmitted. 
     The embodiment of FIG. 4 illustrates the use of an external adapter  15 ′ for a wireless motion detector  10 ′″ that may not require modification of the circuitry of commercially available motion detector  10 ′″. The adapter  15 ′ contains a transceiver  14 ′″, logic circuitry  18 ′″ and another transceiver  32 . In this embodiment, the transmitter  26  is tuned to transmit a different frequency, f 2 , than the frequency f 1  that the receiver  28  at alarm panel  30  is tuned to receive. Transceiver  32  is tuned to receive at f 2  and transmit at f 1 . The adapter receives the transmitted breach indication (transmitted at f 2 ) and retransmits the breach indication at f 1  only if no transponder signal is received by transceiver  14 ′″ in response to a query signal. 
     An example of a wireless motion detector  10 ″ that may be modified as above described, or that may be employed with an adapter  15 ′ as above described, is the Dimango® model RC2070 motion detector available from Lord Henry Enterprises, 5903 Port Andarko Trail, Hermitage, Tenn. 37076 (www.dimango.com). As shown, the wireless motion detectors  10 ″ and  10 ′″ may be battery powered. 
     In alternative embodiments, the breach indication is always permitted to be transmitted in response to motion detection, but the transmitted signals are coded with a first code if a transponder signal was received and with a second code if a transponder signal was not received. The alarm panel is programmed to cause an alarm only if the second code is received. This permits the alarm panel to track movements of transponder equipped objects in protected spaces. 
     Other embodiments are possible and are within the scope of the invention. Accordingly, resort should be had to the following claims, rather than the foregoing description, to ascertain the scope of the invention.