Abstract:
An electronic monitoring system is disclosed for detecting the open and closed conditions of containers or cabinets containing confidential or classified information. The electronic monitoring system includes a current sensor that detects the presence of a locking bar secured to the containers. A current sensor located on each cabinet operatively cooperates with the transmitter that transmits a signal to a central location, which provides an indicator of the secured or non-secured condition of the container.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
   BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention relates to an electronic monitoring system, and more specifically, to a system for monitoring the removal and attachment of a fastener, such as a locking bar, associated with a security container or cabinet, wherein a signal which is unique for each particular cabinet is sent to a centralized monitoring station which keeps track of the fastener status of all cabinets that are being used no matter where they are located. 
   (2) Description of the Prior Art 
   Containers and cabinets housing confidential, classified or even highly classified material commonly employ safety mechanisms that guard against unwanted exposure of the material being housed to adverse contingencies. A common safety mechanism is a fastener, which may be a locking bar, that is arranged with a locking device so that when the bar is attached to the cabinet the drawers being lodged in the cabinets are prevented from moving outward, thereby, making safe to unwanted exposure of the materials therein. 
   The locking bars serve well their intended purpose, but the actual use thereof suffers practical drawbacks. More particularly, sometimes the locking bar is removed to allow the drawers to be opened and the contents thereof revealed to an authorized person, but sometimes the authorized persons forget to reattach the locking bar to the cabinet, thereby exposing the contents of the cabinet to adverse contingencies. Further, the cabinets are sometimes placed at remote locations preventing them from being viewed during conduct of normal activities, thereby, leaving the contents of cabinets susceptible to uncontrolled viewing. Normally, monitoring these remote locations undesirably involves time-consuming tasks of individuals that sometimes suffer from human error drawbacks. It is desired that a monitoring system be provided to determine whether the safety mechanism is in place so as to secure the container or cabinet no matter where the container or cabinet is located. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide for a system for monitoring the status of containers or cabinets housing confidential, classified or highly classified materials. 
   It is a further object of the present invention to provide an electrical status monitoring system that determines the presence or absence of the security mechanism that ensures the security of a container or cabinet, even if the container or cabinet is located at a remote location. 
   It is a further object of the present invention to display the security status information of a secured container or cabinet at a central location. 
   It is a further object of the present invention to provide for an electronic system for monitoring a large number of containers or cabinets containing proprietary or classified documentation located at remote facilities utilized for military or commercial applications. 
   It is a further object of the present invention to provide for a system for monitoring the secured condition of containers or cabinets containing secured information and which does not suffer high labor intensity cost, and human error drawbacks of prior art systems. 
   In accordance with one aspect, an electronic monitor is provided for detecting the presence and absence of a fastener that secures a cabinet with the presence thereof preventing the opening of one or more drawers being housed in the cabinet. The electronic monitor comprises; (a) a first electrode fixed at a predetermined location of the fastener; and (b) a current sensing network having second and third electrodes located in the cabinet in a predetermined manner so that the first electrode contacts both the second and third electrodes when the fastener secures the cabinet. The current sensing network generates current flow and an output signal when the first, second and third electrodes are in contact and which is representative that the fastener is secured. The electronic monitor further comprises a (c) transmitter connected to the output of the current sensing network and generates a predetermined signal of a selected communication system upon detection of a change in current flow. 
   In accordance with another aspect, an electronic monitoring system is provided for detecting and displaying at a central location the presence and absence of one or more fasteners that respectively secure one or more cabinets with the presence thereof preventing the opening of one or more drawers being housed in each of the one or more cabinets. The electronic monitoring system comprises; (a) a first electrode fixed at a predetermined location on each of the respective fasteners; and (b) a current sensing network for each of the one or more cabinets and having second and third electrodes located on a respective cabinet in a predetermined manner so that the first electrode of a respective fastener contacts both the second and third electrodes of its respective cabinet when the respective fastener secures the respective cabinet. The current sensing network generates current flow and an output signal when the first, second and third electrodes are in contact and which is representative that the respective fastener is secured. The electronic monitoring system further comprises a (c) transmitter located on each of the cabinets and connected to the output of a respective current sensing network and generating predetermined signals of a communication link upon detection of a change in said current flow. Each of the transmitters generates predetermined signals which are different from each other. The electronic monitoring system further comprises a (d) receiver located at the central location and accepting and recognizing all of the different predetermined signals of all of the transmitters and generating respective output signals representative of the presence and absence of respective fasteners attached to respective cabinets. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The appended claims particularly point out and distinctly claim the subject matter of this invention. The various objects, advantages and novel features of this invention will be more fully apparent from a reading of the following detailed description in conjunction with the accompanying drawings in which like reference numbers refer to like parts and in which: 
       FIG. 1  is a block diagram of the electronic status monitoring system of the present invention; 
       FIG. 2  illustrates a cabinet having a locking bar attached thereto; 
       FIG. 3  illustrates a schematic of the electronics housed on a cabinet associated with the present invention; and 
       FIG. 4  is a block diagram of the receiver of the electronic status monitoring system of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to the drawings,  FIG. 1  illustrates an electronic monitoring system  10  for detecting and displaying at a central location  12  the presence and absence of fastener devices including bars, locks and clamps located at a remote location  14  and respectively secured to one or more cabinets  16   1 ,  16   2  . . .  16   n , with the presence thereof preventing the opening of one or more drawers being housed in each of the one or more cabinets  16   1 ,  16   2 ,  16   N . 
   More particularly, each of the cabinets  16   1 ,  16   2  . . .  16   N  has a fastener  18 , which in one form may be a locking bar, that secures the contents of a respective cabinet  16  from adverse contingencies and electronics  20  that respectively generate output signals  22   1 ,  22   1  . . .  22   N  which represent the presence and absence of a respective fastener  18  securing a respective cabinet  16 . 
   Each of the output signals  22   1 ,  22   1  . . .  22   N  is accepted and recognized by a receiver  24  at the central location  12 . The receiver  24  generates respective output signals of the received signals which are representative of the presence and absence of the respective fastener  18  securing the respective cabinet  16  and which are displayed, via signal path  26  to respective indicators  28   1 ,  28   2  . . .  28   N  to be further discussed hereinafter with reference to FIG.  4 . 
   The purpose of the electronic monitoring system  10  is to determine whether the fastener, such as a vertical locking bar  18  for a security container or cabinet  16  is attached or unattached with the attachment thereof preventing the contents of cabinets  16  from being viewed. The status of the attached/unattached locking bar  18  is sent back to a central monitor, more particularly, to receiver  24 , which displays the status information. This configuration shown in  FIG. 1  may be used in a military or commercial building to monitor the status of a large number of cabinets  16  containing proprietary or classified documentation no matter where the cabinets  16  are located. In the military where classified information is stored in security containers, such as cabinets  16   1  . . .  16   N  or in the commercial environment where proprietary information may be guarded, as well as secured, there is a need for a centralized monitoring system, such as the electronic monitoring system  10  of the present invention. Further details of the cabinets  16   1 ,  16   2  . . .  16   N  and fasteners  18   1 ,  18   2  . . .  18   N  may be further described with reference to FIG.  2 . 
     FIG. 2  shows one type of cabinet  16  often used for storing classified material having a locking bar  18 , which is secured by passing the locking bar  18  through metal brackets  16 A and  16 B with  16 A being below each drawer  32 ,  34 , and  36  and dimensioned to accept and hold the lower portion of the locking bar  18 . The top of the bar  18  is inserted through bracket  16 B that allows a combination lock  30  to be used to capture and lock the locking bar  18 . The interaction of the locking bar  18  with the electronics  20  may be further described with reference to  FIG. 3 , which illustrates the details of the electronics  20  contained in cabinet  16 , as well as one embodiment of a guidance assembly assisting the mating of the locking bar  18  to the cabinet  16  and comprising magnets  40 A and  40 B. 
   In general, the magnet  40 A is placed on the cabinet  16  with  42  and  44  electrodes attached to the magnet  40 A as shown in FIG.  3 . The other magnet  40 B preferably rests on the surface of the locking bar  18  and has an embedded electrode  46  that makes contact with the other  42  and  44  electrodes when the magnets  40 A and  40 B meet. If desired, the magnet  40 B may be embedded in the locking bar  18 . The magnet  40 B is positioned adjacent and preferably in contact with the electrode  46  and, similarly, the magnet  40 A is positioned adjacent and preferably in contact with the electrodes  42  and  44 . When the locking bar  18  is put in place, an electrical connection is made between the  42  and  44  electrodes in the cabinet  16  and the electrode  46  in the locking bar  18 , and current flows through the circuit included in the electronics  20 , as shown by directional arrows  48  and  50 . When the locking bar  18  is removed, the electrical connection between the first, second and third ( 46 ,  42  and  44 ) is broken and the current becomes 0. The presence of current flow, and more particularly the change in current flow, causes the electronics.  20  to generate signal  22  and which is representative that the locking bar  18  has either been attached (presence) or unattached (absence) to the cabinet  6 . 
   More particularly, with reference to  FIG. 3 , the first electrode  46  is fixed at a predetermined location on the fastener  18  and the second and third electrodes  42  and  44 , respectively are located on the cabinet  16  in a predetermined manner, so that when the locking bar  18  is inserted into the brackets  16 A and  16 B, the first electrode  46  contacts both the second and third electrodes  42  and  44  providing electrical connection therebetween. Conversely, when the locking bar  18  is removed from the cabinet  16  the electrical connection is broken. 
   Although the magnet  40 A, and the bar magnet  40 B perform well in assisting the electrical mating of the electrodes  42 ,  44  and  46 , other devices may be used. For example, the desired mating may be accomplished by mechanical means, such as extensions from the locking bar  18  mating with cutouts in the cabinet  16 . The primary function is to ensure that the first electrode  46  electrically mates with the electrodes  42  and  44  of the current sensing network  52  shown in  FIG. 3  when the locking bar  18  is in place. 
   The current sensing network  52  comprises a source of electrical energy that may be selected from the group consisting of a DC battery  54  and AC excitation  56 , each of which have first and second ends  58  and  60  respectively. The current sensing network  52  further comprises a current sensor  62 , as well as the second and third electrodes  42  and  44  that are spaced apart from each other, with the second electrode  42  connected to the first end  58  of the source of electrical excitation. The third electrode  44  is connected to a second end  64  of the current sensor  62 , which has its first end  66  connected to second end  60  of the source of electrical energy. The current sensor  62  has an output  68  connected to the input of a transmitter  70 . 
   The current sensor  62  operates in a manner known in the art and upon detection of a change in current flow, generates output signal on signal path  68 . The output signal on signal path  68  may also activate a status light  72 . The electronics  20  may further comprise test  74 , which is connected across the electrodes  42  and  44 , as shown in FIG.  3 . The test switch  74 , when depressed, causes current flow which is sensed by current sensor  62  which, in turn, generates an output signal on signal path  68  which, in turn, causes the transmitter  70  to generate the output signal  22 . 
   The transmitter  70  generates a predetermined signal of a selected communication link upon the detection of current flow. The predetermined signal is preferably a radio frequency (RF) signal and the communication link may be selected from the group consisting of a frequency shift key (FSK) technique and an amplitude shift key (ASK) technique. 
   In one embodiment, an FSK sequence of pulses is transmitted by transmitter  70  whenever the current sensor  62  senses a change in the magnitude of the current, such as DC current going from 0 to a positive (+) quantity, or conversely when the DC current goes from a positive (+) quantity to 0. When the current sensor  62  detects a change in the current&#39;s magnitude, the RF transmitter  70  is activated and the FSK pulse stream commences. A short sequence of pulses (10 pulses per sequence), each having a duration of 10 milliseconds in one embodiment, provides a high degree of reliability in the receiver  24  detection capability, to be further described hereinafter with reference to FIG.  4 . An alerting device  88  of  FIG. 4  (also to be further described with reference to  FIG. 4 ) at the centralized status monitor receiver  24  associated with each cabinet  16   1  . . .  16   N  is initialized at installation to the OFF state when the locking bar  18  is put in place for the first time at its respective cabinet  16 . After installation, the alerting device  88  will remain OFF until a sequence of pulses is received, indicating that the cabinet  16   1  . . .  16   N  has been opened; then, the alerting device  88  will be activated to the ON state. Thereafter, the alerting device  88  state will change each time a pulse sequence, in the form of signal  22 , is transmitted by transmitter  70  and received by receiver  24 . 
   A FSK pulse sequence will be transmitted when the locking bar  18  is either removed or put in place and the electrical connection between electrodes  42 ,  44  and  46  is either broken or established. A bit switch device, which may be part of each transmitter  70 , enables one to set the cabinet identification number (e g., 001). More particularly, the transmitter  70  installed in cabinet  16   1 , may be enabled to transmit the binary code 001, whereas the transmitter  70  installed in cabinet  16   8  may be enabled to transmit the binary code 111. The receiver  24 , as well as the alerting device  88 , may be further described with reference to FIG.  4 . 
   The receiver  24  is shown in  FIG. 4 , which illustrates an arrangement for handling cabinets  16   1  . . .  16   8  where each respective transmitter  70  transmits an output signal  22   1 ,  22   2  . . .  22   8 . The receiver  24  comprises an antenna  80 , which receives all the different signals from all the transmitters and provides a respective output thereof. The receiver  24  further comprises a band pass filter  82  that is selected to receive and pass all of the predetermined signals  22   1  . . .  22   8  that are within the selected band of frequencies of interest. The band pass filter  82  provides a respective output for each of its received signals. 
   The receiver  24  further comprises matched filters  84   1 ,  84   2 ,  84   3 ,  84   4 ,  84   5 ,  84   6 ,  84   7 , and  84   8 . Each of the filters  84   1  . . .  84   8  is connected to the output of the band pass filter  82  and each is separately selected to receive and pass a particular wave form comprising an output signal and corresponding to a respective transmitter. For example, matched filter  84   1  is selected to pass the waveform that is particular to the transmitter  70  contained in the electronics  20  of cabinet  16   1 . Each output of the match filter  84   1  . . .  84   8  is routed to a signal processor  86 , which provides respective output signals representative of the presence and absence of the fastener  18  being secured to its respective cabinet  16 . More particularly, for example, if the signal processor  86  receives a signal from the matched filter  84   1  that received signal represents a current change has been sensed by the current sensor  62  in cabinet  16   1 , which, in turn, represents that the locking bar  18   1 , has either been removed (absence) from cabinet  16   1 , or installed (presence) on cabinet  16   1 . The receiver  24  further comprises the cabinet status devices  28   1  . . .  28   8 , previously discussed with reference to FIG.  1  and each of which comprise an alerting device  88  and a cabinet identification (ID)  90 , each having a switch  92  and wherein the cabinet ID  90  displays the associated binary code, e g., 000 for cabinet  16   1 . Each of the cabinets  16   1  . . .  16   8  further preferably are respectively provided with a storage device  94   1  . . .  94   8 , which tracks the number of pulses received. 
   The arrangement shown in  FIG. 4  is associated with a conventional matched filter detector  84   1  . . .  84   8  for eight (8) possible FSK signals (1 per cabinet), a storage device  94  , which tracks and records the number of detection&#39;s in response to the signal processor  86 , and an alerting device  88  showing the status of each cabinet  16  locking bar  18 . 
   In this embodiment, the storage device  94  changes state when 5 out of 10 pulses are detected. At installation, the unique container identifier and FSK frequency sequence is set by using the digital bit set mechanism shown in  FIG. 4 , that is, if the locking bar  18  is in place the associated switch  92  is closed. More particularly, for example, if locking bar  18   1  is in place, then switch  92   1  is closed and the cabinet ID  90   1  is energized indicated by binary code (000). This mechanism sets the specific FSK frequency sequence unique to that cabinet. In one configuration, the code is as follows: f 1  represents 0 and f 2  represents 1. Cabinet  16   1 , more particularly its transmitter  70 , identified as 000 would generate an FSK sequence f 1 , f 1 , f 1 ; cabinet  16   2 , more particularly its transmitter  70 , identified as 001 would generate an FSK sequence f 1 , f 1 , f 2 ; and cabinet  16   8 , more particularly its transmitter  70 , identified as 111 would generate an FSK sequence f 2 , f 2 , f 2 . 
   In another embodiment, the FSK RF signal is replaced by an ASK (amplitude shift key) signal. The number of FSK pulses or ASK pulse per sequence may vary. The detection scheme, which was 5 out of 10 in our example, may be redefined all done in a manner known in the art. 
   It should now be appreciated that the practice of the present invention provides for an electronic monitoring system that allows a fastener, such as a locking bar  18  to be used in an arrangement comprising of a large number of cabinets. The monitoring system  10  enables the security person to obtain information about the status of each cabinet  16 . The electronic monitoring system  10  of the present invention can be implemented at one location using a computer to display the status of each container which, yields the benefits of saving time and effort commonly expended by security persons in a military or commercial complex. 
   It will be understood that various changes and details, steps and arrangement of parts and method steps, which have been described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.