Abstract:
An intrusion sensing device includes an intrusion detection sensor enclosed within a housing and operable to detect an intrusion into a container. A mounting detection mechanism contacts the surface of the container when the housing is mounted thereto and is operable to detect when the housing is not in contact with the surface of the container. An access detection mechanism is operably connected to an access panel of the housing and operable to detect removal of the access panel from the housing. A control module is operable in a setup mode and an active mode. The control module is adapted to receive an alarm message from the intrusion detection sensor and operable to initiate an alarm event during the setup mode which varies from an alarm event initiated during the active mode. A wireless transmitter is operable to transmit an alarm indication signal to a remote monitoring system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/626,757, filed on Nov. 11, 2005. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to intrusion detection sensors, and more particularly to wireless intrusion detection sensors that detect an intrusion of a container. 
     BACKGROUND OF THE INVENTION 
     Construction sites and other industrial job site locations are typically unsecured areas. Loss and theft of tools and other construction equipment is a common occurrence at such sites. For example, a job site may remain exposed to the threat of theft and/or vandalism at night. The tools and/or equipment at an industrial job site typically include very expensive power tools and construction materials. Theft of such items amounts to considerable losses and expenses. While contractors may utilize security guards or guard dogs to ensure the security of tools and other equipment at night, this is very expensive. Additionally, theft and/or vandalism may still occur during the day. 
     Contractors commonly utilize portable containers that house large numbers of tools and other equipment. For example, a contractor may utilize one or more metallic gang boxes. A contractor may attempt to prevent unauthorized access to the insides of containers to safeguard the tools and other equipment. For example, the contractor may utilize devices such as locks, chains, and/or straps to secure the containers. However, unauthorized individuals may still attempt to tamper with such devices during the day or night to gain access to the insides of the containers. Therefore, such devices do not guarantee the security of the containers. Additionally, a contractor may not be aware that attempted thefts have taken place. 
     In one method, a contractor utilizes sensors that detect when containers that house tools or other equipment are opened. One or more sensors may be wired together and communicate with an alarm system. However, since the sensors and the alarm system are wired, such systems are typically applicable only for indoor use. For example, multiple containers may be very far apart on a job site. In this case, long runs of wire are required to link all of the containers to the alarm system, which is very expensive. Additionally, the portable nature of the containers makes wired alarm systems difficult and time consuming to install. 
     SUMMARY OF THE INVENTION 
     An intrusion sensing device according to the present invention is adapted for use with a container and includes an intrusion detection sensor enclosed within a housing and operable to detect an intrusion into a container. The housing is configured to be mounted to a surface of the container. A mounting detection mechanism contacts the surface of the container when the housing is mounted thereto and is operable to detect when the housing is not in contact with the surface of the container. An access detection mechanism is operably connected to an access panel of the housing and operable to detect removal of the access panel from the housing. The access panel provides access to an enclosure the houses a power source for the intrusion sensing device. 
     In other features, a control module is operable in a setup mode and an active mode. The control module is adapted to receive an alarm message from the intrusion detection sensor and operable to initiate an alarm event during the setup mode which varies from an alarm event initiated during the active mode. The control module initiates the alarm event during the setup mode when the control module receives the alarm message from the intrusion detection sensor. The control module receives the alarm message from the intrusion detection sensor when the intrusion detection sensor detects an intrusion into the container. The control module is adapted to receive an alarm message from the mounting detection mechanism and an alarm message from the access detection mechanism. 
     In still other features of the invention, the control module initiates the alarm event during the active mode when the control module receives at least one of the alarm message from the intrusion detection sensor, the alarm message from the mounting detection mechanism, and/or the alarm message from the access detection mechanism. The control module receives the alarm message from the mounting detection mechanism when the housing is not in contact with the surface of the container and the alarm message from the access detection mechanism when the access panel is removed from the housing. A wireless transmitter communicates with the control module and is operable to transmit an alarm indication signal to a remote monitoring system. The wireless transmitter transmits the alarm indication signal to the remote monitoring system during the active mode when the control module receives at least one of the alarm message from the intrusion detection sensor, the alarm message from the mounting detection mechanism, and/or the alarm message from the access detection mechanism. 
     In yet other features, the intrusion detection sensor is a vibration sensor. The control module includes a timer. The control module resets the timer when the control module receives at least one of the alarm message from the intrusion detection sensor, the alarm message from the mounting detection mechanism, and/or the alarm message from the access detection mechanism. The control module does not initiate the alarm event during the setup mode or the alarm event during the active mode and the wireless transmitter does not transmit the alarm indication signal to the remote monitoring system unless the timer is expired. The timer has a first maximum value during the setup mode and a second maximum value during the active mode. The first maximum value is less than the second maximum value. 
     In still other features of the invention, the control module activates an audible indicator during at least one of the alarm event during the setup mode and/or the alarm event during the active mode. The control module sets the audible indicator at a first volume during the setup mode and at a second volume during the active mode. The first volume is less than the second volume. The control module activates a visible indicator during at least one of the alarm event during the setup mode and/or the alarm event during the active mode. The access panel provides access to a sensitivity adjustment mechanism that adjusts a sensitivity of the intrusion detection sensor. The access panel provides access to an actuator that switches the control module between the setup and active modes when the actuator is triggered. The control module automatically operates in the setup mode when the access panel is removed from the housing. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1A  is a top view of an exemplary wireless container intrusion sensor according to the present invention; 
         FIG. 1B  is a bottom view of the container intrusion sensor in  FIG. 1A ; 
         FIG. 1C  is a top view of the container intrusion sensor in  FIG. 1A  with an access panel removed; 
         FIG. 1D  is a side view of the container intrusion sensor in  FIG. 1A  with the access panel removed; 
         FIG. 2  is a functional block diagram of a wireless intrusion detection system according to the present invention; 
         FIG. 3  is a flowchart illustrating steps performed by the control module to activate an alarm indicator; 
         FIG. 4  is a functional block diagram and electrical schematic of an exemplary vibration sensor; 
         FIG. 5  is a flowchart illustrating steps performed by the control module to utilize a false trip filter before activating an alarm indicator; and 
         FIG. 6  illustrates communications between the container intrusion sensor and a remote monitoring system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module and/or device refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Referring to  FIGS. 1A-1D , an exemplary container intrusion sensor  10  detects a security breach of a container. For example, the container intrusion sensor  10  detects the intrusion of the container on which the container intrusion sensor  10  is mounted. In this case, an intrusion is detected when the container is opened and/or when objects are removed from the container. The container intrusion sensor  10  initiates an alarm event when an intrusion is detected. For example, the container intrusion sensor  10  may activate an alarm indicator during the alarm event. The container intrusion sensor  10  also wirelessly communicates with a remote monitoring system to indicate the intrusion. As shown in  FIG. 1A , the container intrusion sensor  10  includes holes  12  that pass through the housing of the container intrusion sensor  10 . The holes  12  allow the container intrusion sensor  10  to be fastened to a surface of a container. For example, screws or other fasteners may be utilized to fasten the container intrusion sensor  10  to a surface of a container. 
     Portions of the holes  12  are preferably recessed with respect to a top surface of the container intrusion sensor  10  so that the top surface remains flush. The container intrusion sensor  10  includes an access panel  14  that prevents unauthorized access to interior controls of the container intrusion sensor  10 . The access panel  14  rotates about a hinge  16  and snaps open and shut against the surface of the container intrusion sensor  10  with a finger latch  18 . A screw  20  also fastens the access panel  14  shut to deter unauthorized access to the interior controls of the container intrusion sensor  10 . 
     As shown in  FIG. 1B , a bottom surface of the container intrusion sensor  10  includes magnets  20  that allow the container intrusion sensor  10  to be removably fixed to a surface of a container that is metallic. For example, the magnets  20  may hold the container intrusion sensor  10  in place while screws are utilized to fasten the container intrusion sensor  10  to the container. The bottom surface of the container intrusion sensor  10  also includes a surface tamper device  22 . The surface tamper device  22  detects when the container intrusion sensor  10  is removed from a surface of a container. In an exemplary embodiment, the surface tamper device  22  includes a plunger  24  that is spring-loaded. Therefore, the plunger  24  extends past the bottom surface of the container intrusion sensor  10  when the container intrusion sensor  10  is not mounted on a surface of a container. The plunger  24  includes a magnet that closes a circuit of an internal control module when the container intrusion sensor  10  is mounted on a surface of a container. The circuit opens when the plunger  24  extends past the bottom surface of the container intrusion sensor  10 , which initiates an alarm event. 
     The bottom surface of the container intrusion sensor  10  includes a notch  26 . An audible indicator  28  is mounted in the notch  26  so that the bottom surface of the container intrusion sensor  10  remains flush. For example, the audible indicator  28  may be a speaker or another audible indicator. The audible indicator  28  is activated when the surface tamper device  22  detects that the bottom surface of the container intrusion sensor  10  no longer contacts a surface of a container. 
     As shown in  FIG. 1C , the access panel  14  is used to access an interior compartment of the container intrusion sensor  10 . A control panel  30  includes a sensitivity adjustment device  32 . The sensitivity adjustment device  32  adjusts a sensitivity of a vibration sensor that is housed inside the container intrusion sensor  10 . For example, the sensitivity adjustment device  32  may be a sliding control that adjusts a resistance of a rheostat in the vibration sensor. Alternatively, the sensitivity adjustment device  32  may include one or more buttons that communicate with a control module to increase/decrease the sensitivity of the vibration sensor when pressed. 
     The vibration sensor detects an intrusion of a container on which the container intrusion sensor  10  is mounted. The container intrusion sensor  10  activates the audible indicator  28  when the vibration sensor detects an intrusion. The container intrusion sensor  10  is capable of operating in a setup mode and a active mode, as will be described in further detail below. During the setup mode, the sensitivity of the internal vibration sensor may be adjusted so that the container intrusion sensor  10  functions as desired. The control panel  30  also includes an actuator  34 . For example, the actuator  34  may be a push-button, a toggle switch, or another actuator. The container intrusion sensor  10  switches between the setup and active modes when the actuator  34  is triggered. 
     The control panel  30  also includes a visible indicator  36 . The visible indicator  36  indicates when the vibration sensor detects an intrusion during the setup mode. For example, the visible indicator  36  may be a light-emitting diode (LED) or another visible indicator. In this case, it is not necessary for the container intrusion sensor  10  to activate the audible indicator  28  during the setup mode. Alternatively, the container intrusion sensor  10  may activate the audible indicator  28  at a lower volume during the setup mode than during the active mode. 
     The interior compartment also allows access to a battery compartment  38  that houses one or more batteries to power the container intrusion sensor  10 . The interior compartment also includes an access tamper device  40 . The access tamper device  40  detects when the access panel  14  is open. The access tamper device  40  includes a notch  42  that receives a magnet mounted on the access panel  14  when the access panel  14  is closed. The presence of the magnet in the notch  42  closes a circuit of an internal control module when the access panel  14  closed. The circuit opens when the access panel  14  is opened and the magnet is removed from the notch  42 , which initiates an alarm event. For example, the container intrusion sensor  10  activates the audible indicator  28  during the active mode when the access tamper device  40  detects that the access panel  14  is open. 
     In an exemplary embodiment, the container intrusion sensor  10  includes a housing comprising two sections  44 - 1  and  44 - 2 . The two sections  44 - 1  and  44 - 2  are preferably environmentally sealed to prevent water and/or dust from entering the inside of the container intrusion sensor  10 . For example, a gasket seal along the perimeter of the container intrusion sensor  10  between the two sections  44 - 1  and  44 - 2  provides an effective seal. Additionally, the container intrusion sensor  10  may include tamper-proof fasteners that prevent unauthorized separation of the two sections  44 - 1  and  44 - 2 . The housing of the container intrusion sensor  10  is preferably rugged, durable, and able to withstand a wide range of temperature variations. 
     Referring now to  FIG. 2 , the container intrusion sensor  10  includes an intrusion detection system  52  according to the present invention. The intrusion detection system  52  includes a control module  54  that communicates with a vibration sensor  56 . The vibration sensor  56  detects an intrusion of a container on which the container intrusion sensor  10  is mounted. The vibration sensor  56  transmits an alarm message to the control module  54  when an intrusion is detected. The sensitivity adjustment device  32  communicates with the vibration sensor  56  and adjusts a sensitivity of the vibration sensor  56 . For example, if the sensitivity of the vibration sensor  56  is increased, the vibration sensor  56  is more likely to detect an intrusion when less vibration is generated as compared to the original sensitivity setting. The sensitivity adjustment device  32  does not adjust the actual sensitivity of a sensing element included in the vibration sensor. Rather, the sensitivity adjustment device  32  adjusts the way a signal generated by the sensing element is processed in order to detect only vibrations that are greater than a desired magnitude, as will be described in further detail below. 
     The control module  54  communicates with the access tamper device  40 . The access tamper device  40  detects when the access panel  14  to the interior compartment of the container intrusion sensor  10  is open. If the access panel  14  is open, the access tamper device  40  transmits an alarm message to the control module  54 . The control module  54  also communicates with the surface tamper device  22 . The surface tamper device  22  detects when the container intrusion sensor  10  is removed from a surface of a container. When the container intrusion sensor  10  is removed from a surface of a container, the surface tamper device  22  transmits an alarm message to the control module  54 . 
     The control module  54  operates in setup and active modes. The actuator  34  on the control panel  30  switches the control module  54  between the setup and active modes when the actuator  34  is triggered. The control module  54  communicates with an alarm indicator  58  and a wireless transceiver  60 . For example, the wireless transceiver  60  may be a radio frequency (RF) transceiver. However, those skilled in the art can appreciate that the wireless transceiver  60  may communicate in any wireless communications frequency such as 900 MHz. Additionally, the wireless transceiver  60  may utilize one-way or two-way wireless communications. The alarm indicator  58  may include the visible indicator  36 , the audible indicator  28 , and/or another type of alarm indicator  58 . 
     The wireless transceiver  60  wirelessly communicates with a remote monitoring system. In an exemplary embodiment, the wireless transceiver  60  is manufactured by Inovonics Wireless Corporation and utilizes “EchoStream” multiple frequency technology. However, other wireless transceivers  60  may be used. The control module  54  activates the alarm indicator  58  during the setup mode when the vibration sensor  56  detects an intrusion. In an exemplary embodiment, the control module  54  does not activate the alarm indicator  58  during the setup mode when the access tamper device  40  detects that the access panel  14  is open or when the surface tamper device  22  detects that the container intrusion sensor  10  is removed from a surface of a container. This is because the access panel  14  is typically open and/or the container intrusion sensor  10  is not mounted on a surface of a container during testing of the container intrusion sensor  10 . 
     The control module  54  activates the alarm indicator  58  during the active mode when the vibration sensor  56  detects an intrusion, the access tamper device  40  detects that the access panel  14  is open, and/or the surface tamper device  22  detects that the container intrusion sensor  10  is not mounted on a surface of a container. In an exemplary embodiment and when the alarm indicator  58  is the audible indicator  28 , the control module  54  activates the audible indicator  28  at a first volume during the setup mode and at a second volume during the active mode. For example, the first volume may be less than the second volume. This is because it is not necessary for the audible indicator  28  to be very loud during testing of the container intrusion sensor  10 . 
     The wireless transceiver  60  transmits an intrusion indication signal to the remote monitoring system during the active mode when the vibration sensor  56  detects an intrusion, the access tamper device  40  detects that the access panel  14  is open, and/or the surface tamper device  22  detects that the container intrusion sensor  10  is removed from a surface of a container. In an exemplary embodiment, the wireless transceiver  60  does not transmit the intrusion indication signal to the remote monitoring system during the setup mode. This prevents unnecessary intrusion indication to the remote monitoring system during testing and conserves power. 
     The control module  54  includes a timer  62 . The timer  62  is reset when the control module  54  activates the alarm indicator  58 . The control module  54  does not activate the alarm indicator  58  unless the timer  62  is expired. Additionally, the wireless transceiver  60  does not transmit the intrusion indication signal to the remote monitoring system unless the timer  62  is expired. This prevents the control module  54  and the wireless transceiver  60  from redundantly indicating an intrusion of a container when the intrusion is continuously detected. 
     As long as an intrusion is detected while the timer  62  is running, the timer  62  is reset. After the timer  62  expires and another intrusion is detected, the control module  54  and/or the wireless transceiver  60  indicate an intrusion again. The maximum value of the timer  62  during the setup mode is preferably less than the maximum value of the timer  62  during the active mode. For example, the maximum value of the timer  62  may be 1 second during the setup mode and 10 minutes during the active mode. This expedites a procedure to test the container intrusion sensor  10 . 
     Referring now to  FIG. 3 , an intrusion detection algorithm begins in step  70 . In step  72 , the control module  54  initializes the value of the timer  62  so that the timer  62  is expired. In step  74 , the control module  54  checks for alarm messages from the vibration sensor  56 , the surface tamper device  22 , and the access tamper device  40 . In step  76 , the control module  54  determines whether a security breach has been detected. If the vibration sensor  56  does not detect a security breach, control returns to step  74 . If the vibration sensor  56  detects a security breach, the control module  54  determines whether the timer is expired in step  78 . If the timer  62  is not expired, the control module  54  resets the timer  62  in step  80  and control returns to step  74 . If the timer  62  is expired, control determines whether the control module  54  is operating in the setup mode in step  82 . 
     If the control module  54  is operating in the setup mode, control proceeds to step  84 . In step  84 , the control module  54  initiates an alarm event associated with the setup mode and loads the setup mode maximum timer  62  value. For example, the control module  54  may activate the visible indicator  36  and activate the audible indicator  28  at a first volume during the alarm event associated with the setup mode. If the control module  54  is operating in the active mode, control proceeds from step  82  to step  86 . 
     In step  86 , the control module  54  initiates an alarm event associated with the active mode and loads the active mode maximum timer  62  value. For example, the control module  54  may activate the audible indicator  28  at a second volume during the alarm event associated with the active mode. Alternatively or additionally, the wireless transceiver  60  may transmit an alarm indication signal to a remote monitoring system during the alarm event associated with the active mode. Control proceeds from both steps  84  and  86  to step  88 . In step  88 , the control module  54  resets the timer  62  and control returns to step  74 . 
     Referring now to  FIG. 4 , an exemplary vibration sensor  56  includes a sensing element  96 . The sensing element  96  generates a first vibration signal. A value of the first vibration signal is based on a level of vibration that the sensing element  96  senses. The sensing element  96  includes a vibration detection element  98 . For example, the vibration detection element  98  may be a piezoelectric device. A first terminal of the vibration detection element  98  connects to a ground potential. 
     A transimpedance amplifier  100  receives the first vibration signal, performs preliminary amplification, and generates a first amplified vibration signal. The transimpedance amplifier  100  includes a first operational amplifier (opamp)  102 , a first resistor  104  and a first capacitor  106 . A second terminal of the vibration detecting element  98  connects to a first input of the first opamp  102 , a first end of the first resistor  104 , and a first end of the first capacitor  106 . A first power terminal of the first opamp  102  connects to a supply potential. A second power terminal of the first opamp  102  and a second input of the first opamp  102  connect to a ground potential. 
     A gain amplifier  108  receives the first amplified vibration signal, performs adjustable amplification, and generates a second amplified vibration signal. The vibration sensor  56  optionally includes a filter between the transimpedance amplifier  100  and the gain amplifier  108  that filters the first amplified vibration signal. The sensitivity adjustment device  32  connects to the gain amplifier  108  and adjusts a gain of the gain amplifier  108  to adjust the sensitivity. 
     The gain amplifier  108  includes a second opamp  110  and a second resistor  112 . An output of the first opamp  102  connects to a second end of the first resistor  104 , a second end of the first capacitor  106 , and a first input of the second opamp  110 . The sensitivity adjustment device  32  includes an adjustable resistor  114 . For example, the adjustable resistor  114  may be a rheostat device. A first end of the second resistor  112  connects to a ground potential. A second end of the second resistor  112  connects to a second input of the second opamp  110  and a first end of the adjustable resistor  114 . 
     A threshold comparison module  116  receives the second amplified vibration signal and compares a value of the second amplified vibration signal to a threshold to determine when an intrusion occurs. The threshold comparison module  116  generates an intrusion detection signal. A value of the intrusion detection signal indicates whether the vibration sensor  56  detects an intrusion. The threshold comparison module  116  includes a Schmidt trigger device  118 . An output of the second opamp  110  connects to a second end of the adjustable resistor  114  and an input of the Schmidt trigger device  118 . A first bias terminal of the Schmidt trigger device connects to a supply potential. A second bias terminal of the Schmidt trigger device connects to a ground potential. The control module  54  detects the alarm message from the vibration sensor  56  based on the output of the Schmidt trigger. 
     Referring now to  FIG. 5 , there may be situations where the vibration sensor  56  is particularly susceptible to background noise and vibration. For example, thunder or a falling tree branch may generate sufficient vibration to produce a false security breach detection. Therefore, in an exemplary embodiment of the invention, the control module  54  initiates a waiting period after an initial detection of a security breach. For example, the waiting period may be set equal to ten seconds or another amount of time. During the waiting period, the control module  54  inhibits detection of a threshold trigger in the vibration sensor  56  for a predetermined period of time each time a security breach is detected. For example, the control module  54  may inhibit detection of a threshold trigger for 250 ms or another amount of time each time a security breach is detected. 
     After the control module  54  no longer inhibits detection of a threshold trigger, the control module  54  determines whether another security breach is detected. If the control module  54  detects a predetermined number of security breaches during the waiting period, the control module  54  proceeds to initiate an alarm event. For example, the control module  54  may detect 3 security breaches or another number of security breaches during the waiting period before initiating an alarm event. Otherwise, the original security breach is deemed a false alarm and the control module  54  initiates another full waiting period on a subsequent detection of a security breach. 
     A filtered intrusion detection algorithm begins in step  130 . In step  132 , the control module  54  checks for alarm messages from the vibration sensor  56 , the surface tamper device  22 , and the access tamper device  40 . In step  134 , the control module  54  determines whether a security breach has been detected. If the vibration sensor  56  does not detect a security breach, control returns to step  132 . If the vibration sensor  56  detects a security breach, the control module resets the timer and sets the term N equal to 1 in step  136 . For example, the timer may be reset to count down from ten seconds. In step  138 , the control module  54  inhibits detection of a threshold trigger in the vibration sensor  56  for a predetermined period of time. For example, the control module  54  may inhibit detection of the threshold trigger for 250 ms. 
     In step  140 , the control module  54  determines whether a security breach has been detected. If true, control proceeds to step  142 . If false, the control module determines whether the timer is expired in step  144 . If false, control returns to step  140 . If true, control returns to step  132 . In step  142 , the control module increments the value of N. In step  146 , the control module determines whether N is equal to 3. If false, control returns to step  138 . If true, control determines whether the control module  54  is operating in the setup mode in step  148 . If true, control proceeds to step  150 . If false, the control module  54  initiates an alarm event associated with the active mode in step  152  and control returns to step  132 . In step  150 , the control module  54  initiates an alarm event associated with the setup mode and control returns to step  132 . While the filtered intrusion detection algorithm illustrated in  FIG. 5  only includes a single timer, a second timer may be incorporated to ensure a minimum amount of time between alarm events as shown in  FIG. 3 . 
     Referring now to  FIG. 6 , a portable container  160  houses assets  162 . For example, the assets  162  may include tools or other construction materials on a job site. The container intrusion sensor  10  is mounted on an outer surface of the lid  164  on the portable container  160 . However, the container intrusion sensor  10  may be mounted in other locations. An antenna  166  of the wireless transceiver  60  in the container intrusion sensor  10  is diagrammatically shown communicating with an antenna  168  of a monitoring station  170 . The monitoring station  170  monitors a condition of the container intrusion sensor  10 . The monitoring station  170  detects an intrusion of the portable container  160  when the wireless transceiver  60  transmits an intrusion indication signal  172  to the monitoring station  170 . 
     A user of the monitoring station  170  may activate an alarm or contact law enforcement authorities or job site personnel upon receipt of the intrusion indication signal  172 . Alternatively or additionally, the monitoring station  170  may automatically activate an alarm or contact appropriate parties. For example, the monitoring station  170  may automatically e-mail, page, voice dial, and/or text message a job site supervisor. The monitoring station  170  may be programmed to only take responsive action during certain times of day. For example, the monitoring station  170  may be programmed to only take responsive action during the night since the portable container  160  might only be used during the day. In an exemplary embodiment, the monitoring station  170  simultaneously communicates with multiple container intrusion sensors  10  that are fixed to portable containers  160  to monitor a large number of assets  162  across a large distance. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.