Patent Publication Number: US-2010127873-A1

Title: Alarm systems, wireless alarm devices, and article security methods

Description:
CLAIM FOR PRIORITY 
     This application is a continuation of U.S. patent application Ser. No. 11/788,235, filed Apr. 19, 2007; which application claims priority from U.S. Provisional Application Ser. No. 60/795,851, filed Apr. 28, 2006; the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to alarm systems, wireless alarm devices, and article security methods. 
     BACKGROUND 
     Theft detection electronic systems have been used in numerous applications including for example consumer retail applications to deter theft. Some theft detection electronic systems may operate in frequency bands susceptible to electromagnetic interference emitted from sources other than components of the systems. The interference may degrade the operations of the theft detection electronic systems resulting in unreliable operation including signaling of false alarms. Electromagnetic interference may result from different possible sources including for example cellular or cordless telephones or pagers. The impact of these interference sources may be significant in view of the increasing popularity and usage of these devices, including usage by individuals in areas which are secured. 
     The present disclosure describes apparatus and methods which provide improved communications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure are described below with reference to the following accompanying drawings. 
         FIG. 1  is an illustrative representation of an alarm system according to one embodiment. 
         FIG. 2  is a functional block diagram of a remote communication device according to one embodiment. 
         FIG. 3  is a functional block diagram of conditioning circuitry of a remote communication device according to one embodiment. 
         FIG. 4  is a schematic diagram of conditioning circuitry of a remote communication device according to one embodiment. 
         FIG. 5  is a map showing how  FIGS. 5   a  and  5   b  are to be assembled. Once assembled,  FIGS. 5   a  and  5   b  are a flow chart of a method performed by a remote communication device according to one embodiment. 
         FIG. 6  is a schematic diagram of monitoring circuitry of a remote communication device according to one embodiment. 
         FIG. 7  is a schematic diagram of conditioning circuitry of a remote communication device according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The reader is directed to other U.S. patent applications entitled “Alarm Systems, Wireless Alarm Devices, And Article Security Methods”, naming Ian R. Scott, Brian J. Green and Dennis D. Belden, Jr. as inventors, having attorney docket number 1796154US2AP, and filed the same day as the present application, and entitled “Alarm Systems, Remote Communication Devices, And Article Security Methods”, naming Ian R. Scott, Brian J. Green and Dennis D. Belden, Jr. as inventors, having attorney docket number 1796157US2AP, and filed the same day as the present application, and the teachings of both of which are incorporated by reference herein. 
     Referring to  FIG. 1 , an exemplary configuration of an alarm system according to one illustrative embodiment of the disclosure is shown with respect to reference  10 . Alarm system  10  includes a base communication device  12  and one or more remote communication devices  14  remotely located with respect to base communication device  12  (only one device  14  is shown in  FIG. 1 ). Remote communication devices  14  may be portable and moved with respect to base communication device  12  in one embodiment and may be referred to as wireless alarm units or devices in some configurations. Base and remote communication devices  12 ,  14  are configured to implement wireless communications including radio frequency communications with respect to one another in the described embodiment. 
     In one exemplary implementation, alarm system  10  may be used to secure a plurality of articles (not shown). In a more specific example, alarm system  10  may be implemented in a consumer retail application to secure a plurality of articles including consumer items offered for sale. In some applications, a plurality of remote communication devices  14  may be used to secure a plurality of respective articles. The remote communication devices  14  may be individually associated with an article, for example, by attaching the remote communication device  14  to the article to be secured in one embodiment. 
     In one embodiment, alarm system  10  may be implemented to secure the articles which are to be maintained in a given location until authorization is provided to remove the articles from the location. For example, the alarm system  10  may be associated with a room, such as a retail store, and it may be desired to maintain the articles within a defined area (e.g., within the inside of the store) and to generate an alarm if an unauthorized attempt to remove an article from the defined area is detected. One exemplary configuration of alarm system  10  used in a retail article monitoring implementation is Electronic Article Surveillance (EAS). Alarm system  10  may implement different types of EAS monitoring in different embodiments. Examples of different configurations of EAS include AM (Acousto-Magnetic), EM (electro-magnetic), and RF (Radio-Frequency). 
     Accordingly, in one embodiment, the base communication device  12  may be proximately located to an ingress and egress point  16  of a room. In the exemplary depicted embodiment, base communication device  12  includes a plurality of gates  18  located adjacent the ingress and egress point  16  (e.g., gates  18  may be positioned at opposing sides of a doorway of a retail store). In the described implementation, the gates  18  may emit wireless signals which define the secured area at the ingress and egress point  16  such that remote communication devices  14  pass through the secured area if they are brought into or removed from the defined area corresponding to the interior of the store (e.g., a defined area containing secured articles may be to the right of gates  18  in  FIG. 1  and the left side of the gates may be unsecured). In one embodiment, a plurality of base communication devices  12  may be used to secure a single room or area if a plurality of points of ingress/egress are provided for the room or area. 
     Alarm system  10  is configured to generate an alarm responsive to the presence of one of the remote communication devices  14  being detected within a secured area. As described further below, the secured area may correspond to a range of wireless communications of gates  18  of base communication device  12 , and in one example mentioned above, the gates  18  may be located adjacent an ingress and egress point  16  of a room containing secured articles. The base communication device  12  may emit wireless signals within and corresponding to the secured area and remote communication devices  14  brought into the secured area receive the wireless signals and may emit alarm signals in response to receiving the wireless signals. Accordingly, the secured area may be defined and used in one embodiment to generate alarms when remote communication devices  14  are adjacent to the ingress and egress point  16  in one configuration (i.e., generating an alarm to indicate a potential theft of an item by the bringing of the article having the remote communication device  14  attached thereto within the communications range of the base communication device  12  corresponding to the secured area). 
     Referring to  FIG. 2 , an exemplary configuration of a remote communication device  14  is shown according to one embodiment. In the illustrated configuration, remote communication device  14  includes a tag  20  coupled with an alarm device  22 . A housing, such as a plastic case (e.g., corresponding to the box labeled as reference  14  in  FIG. 2  in one embodiment), may be formed to house and protect one or both of tag  20  and alarm device  22  and the housing may be used to couple, attach, or otherwise associate the remote communication device  14  with an article to be secured. In exemplary embodiments, the housing may encase some or all of the components of device  14  while in other embodiments the housing may operate to support the components without encasing them. Any suitable housing to support components of device  14  may be used. Alarm device  22  includes conditioning circuitry  30 , processing circuitry  32 , storage circuitry  34 , alarm circuitry  36  and a power source  38  in the exemplary depicted embodiment. Power source  38  may be provided in the form of a battery and coupled to provide operational electrical energy to one or more of conditioning circuitry  30 , processing circuitry  32 , storage circuitry  34  and/or alarm circuitry  36  in exemplary embodiments. Additional alternative configurations of remote communication device  14  and alarm device  22  are possible including more, less and/or alternative components in other embodiments. 
     Tag  20  is configured to implement wireless communications with respect to base communication device  12  in the described embodiment. In one construction, tag  20  includes an antenna circuit in the form of a parallel LC resonant circuit configured to resonate responsive to electromagnetic energy emitted by base communication device  12  (e.g., the inductor and capacitor may be connected in parallel between the nodes of R 1  and ground in  FIG. 4  in one embodiment). In one configuration, the inductor of the antenna circuit is a solenoid wire wound inductor configured to resonate at frequencies of communication of base communication device  12 . In one embodiment, exemplary tags  20  may include electronic article surveillance (EAS) devices which are commercially available from numerous suppliers. As discussed further below, remote communication device  14  may generate a human perceptible alarm signal responsive to resonation of the antenna circuit. The alarm signal may indicate the presence of the remote communication device  14  (and associated article if provided) within a secured area, such as a doorway of a retail store. 
     Base communication device  12  is configured to emit electromagnetic energy for interaction with remote communication devices  14  to implement security operations. Base communication device  12  may omit the electromagnetic energy in the form of a wireless signal which has a different frequency at different moments in time. In one configuration, base communication device  12  emits a carrier frequency (e.g., less than 55 MHz) which may be frequency modulated wherein the carrier sweeps sinusoidally within a frequency range from a lower frequency to an upper frequency. For example, in one possible RF EAS implementation, base communication device  12  may emit a wireless signal in the form of a 8.2 MHz carrier which is FM modulated to sweep within a range between +1-500 kHz of 8.2 MHz at a rate of 60 Hz. In another embodiment, base communication device  12  may omit bursts of electromagnetic energy at different frequencies in the desired band of 8.2 MHz +1-500 kHz. Communications intermediate base and remote communication devices  12  and  14  may occur at other frequencies in other embodiments (e.g., AM EAS arrangements may communicate within a range of 55-58 kHz). 
     Remote communication devices  14  are individually configured to resonate at a range of frequencies within the modulated frequency range of the carrier signal emitted by the base communication device  12 . For example, the LC components of the tag  20  may be tuned to resonate when the tag  20  is located within the secured area (and accordingly receives the electromagnetic energy emitted by the base communication device  12 ) and the carrier signal corresponds to the resonant frequency of the tag  20 . In one embodiment, the resonation may be detected by the base communication device  12  and may trigger the base communication device  12  to generate a human perceptible alarm. 
     The resonation of tag  20  results in the generation of a reference signal which is communicated to alarm device  22  resident within the remote communication device  14  in one embodiment. The reference signal may include a signature (e.g., pattern of bursts) of alternating current energy corresponding to the carrier frequency of the signal communicated by base communication device  12  and at moments in time wherein the carrier frequency is equal to the resonant frequency of the tag  20 . The reference signal may be communicated to conditioning circuitry  30  which may generate a pattern of plural identifiable components (e.g., pulses) individually corresponding to one of the bursts of AC energy. The pulses are received by processing circuitry  32  which may analyze the pulses in an attempt to distinguish pulses corresponding to electromagnetic energy emitted from the base communication device  12  from pulses resulting from electromagnetic energy of other sources, for example, corresponding to noise or interference. Upon detection of the receipt by device  14  of electromagnetic energy from base communication device  12 , processing circuitry  32  may control alarm circuitry  36  to emit a human perceptible alarm. 
     In one embodiment, processing circuitry  32  is arranged to process data, control data access and storage, issue commands, and control other desired operations of remote communication device  14 . Processing circuitry  32  may monitor signals which correspond to communications of base communication device  12 . As discussed further below and according to one exemplary embodiment, processing circuitry  32  may analyze a pulse stream generated by conditioning circuitry  30  for pulse length and duty cycle. Processing circuitry  32  may use a discriminating window method which specifies a minimum number of pulses from a detected sequence to be within a set of parameters describing pulse on and off timing. Additional details of one exemplary analysis are described in detail below. Processing circuitry  32  may control the emission of an alarm signal by the remote communication device  14  if predefined parameters are met as discussed further below. 
     Processing circuitry  32  may comprise circuitry configured to implement desired programming provided by appropriate media in at least one embodiment. For example, the processing circuitry  32  may be implemented as one or more of a processor and/or other structure configured to execute executable instructions including, for example, software and/or firmware instructions, and/or hardware circuitry. Exemplary embodiments of processing circuitry  32  include hardware logic, PGA, FPGA, ASIC, state machines, and/or other structures alone or in combination with a processor. These examples of processing circuitry  32  are for illustration and other configurations are possible. 
     Storage circuitry  34  is configured to store programming such as executable code or instructions (e.g., software and/or firmware), electronic data, databases, or other digital information and may include processor-usable media. Processor-usable media may be embodied in any computer program product(s) or article of manufacture(s) which can contain, store, or maintain programming, data and/or digital information for use by or in connection with an instruction execution system including processing circuitry in the exemplary embodiment. For example, exemplary processor-usable media may include any one of physical media such as electronic, magnetic, optical, electromagnetic, infrared or semiconductor media. Some more specific examples of processor-usable media include, but are not limited to, a portable magnetic computer diskette, such as a floppy diskette, zip disk, hard drive, random access memory, read only memory, flash memory, cache memory, and/or other configurations capable of storing programming, data, or other digital information. 
     At least some embodiments or aspects described herein may be implemented using programming stored within appropriate storage circuitry  34  described above and/or communicated via a network or other transmission media and configured to control appropriate processing circuitry. For example, programming may be provided via appropriate media including, for example, embodied within articles of manufacture, embodied within a data signal (e.g., modulated carrier wave, data packets, digital representations, etc.) communicated via an appropriate transmission medium, such as a communication network (e.g., the Internet and/or a private network), wired electrical connection, optical connection and/or electromagnetic energy, for example, via a communications interface, or provided using other appropriate communication structure or medium. Exemplary programming including processor-usable code may be communicated as a data signal embodied in a carrier wave in but one example. 
     As mentioned above, alarm circuitry  36  may be configured to emit a human perceptible alarm signal (e.g., to notify interested parties of the fact that an article has been moved into a secured area). For example, alarm circuitry  36  may include an audible alarm and/or a visual alarm individually configured to emit human perceptible alarm signals. 
     Referring to  FIG. 3 , exemplary components of one embodiment of conditioning circuitry  30  intermediate tag  20  and processing circuitry  32  are shown. The illustrated conditioning circuitry  30  includes a detector  40 , amplifier  42 , and pulse shaper  44 . Detector  40  is configured to detect the presence of the wireless communications generated by base communication device  12 . In one embodiment, detector  40  is an RF detector configured to detect relatively low power signals (millivolt level). Detector  40  is configured to output second electrical signals corresponding to the received first electrical signals. As described below, the detector  40  may comprise a non-linear detector and the second electrical signals may have a non-linear relationship to the first electrical signals. 
     Amplifier  42  is configured to generate digital signals from the bursts of AC provided by the tag  20  and using the second electrical signals outputted by detector  40  in the illustrated embodiment. Pulse shaper  44  is configured to process the output of the amplifier  42  to assist processing circuitry  32  with detection of identifiable components (e.g., pulses) within the reference signal in the form of the second electrical signals. Additional details of the components of  FIG. 3  are discussed immediately below in one embodiment. 
     Referring to  FIG. 4 , an exemplary configuration of conditioning circuitry  30  is shown. In the illustrated embodiment of  FIG. 4 , exemplary implementations of detector  40 , amplifier  42  and pulse shaper  44  are shown. Detector  40  includes D 1 , L 1 , C 4 , amplifier  42  includes comparator U 1 , and pulse shaper includes D 2  in the depicted arrangement. The illustrated circuit provides sensitivity to signals from base communication device  12  in the milliVolt range while providing a detector  40  which is passive and consumes substantially no power from power source  38 . Other circuits are possible including more, less and/or alternative components. 
     During operation, output of tag  20  due to resonation with electromagnetic energy is detected by a non-linear device comprising diode D 1  in the depicted embodiment. More specifically, coupling capacitor C 2  connects signals generated by tag  20  to the detector  40  while allowing for a DC shift which becomes the output signal. Diode D 1  conducts in a forward biased direction when the RF signal received by tag  20  is negative thereby clamping the waveform to ground and is non-conducting when the RF signal is positive thereby developing a positive signal corresponding to the instantaneous value of the peak of the RF waveform (e.g., 8.2 MHz) generated by base communication device  12  for half of the wave cycle thereby providing a DC or slowly varying AC waveform that is proportional to the amplitude of the RF signal received by tag  20 . The inclusion of a non-linear element D 1  in the detector  40  improves the sensitivity of alarm device  22  of remote communication device  14 . In one embodiment, the described diode D 1  provides a non-linear relationship wherein current through diode D 1  is clamped to ground during the negative half cycle and allowed to swing positive during the positive half cycle of received voltage corresponding to input signals received from tag  20  and an output signal is provided to C 4  which is therefore proportional to the positive peak value of the received signal. The detected DC component signal is DC coupled and AC blocked by the inductor to C 4 . C 4  holds the value of the detected voltage. Accordingly, in one embodiment, C 4  of detector  40  is configured to generate an envelope of the signal and generally resemble a square wave following the macro trend of the RF envelope of signals received from base communication device  12 . 
     In the depicted embodiment, C 3  is coupled across the inductor L 1  and is selected to provide parallel resonance of the component combination at the band of frequencies that are transmitted by base communication device  12  thereby increasing the AC impedance of the circuit connected to tag  20 . The increased impedance reduces loading of tag  20  so that the voltage developed across it is higher thereby improving sensitivity and providing increased reflection by the antenna circuitry of tag  20  of signals to base communication device  12 . The provision of detector  40  comprising a non-linear detector through the use of diode D 1  generates pulses having an absolute value relation to the signal received by the antenna circuit and applies the pulses to comparator U 1  in one embodiment. Detector  40  has a non-linear transfer characteristic in the described embodiment where the input and output of the detector  40  have an absolute value or logarithmic relationship through the use of diode D 1  in one embodiment. 
     The detector  40  described according to one embodiment provides increased sensitivity to wireless communications of base communication device  12  without the use of amplifiers operating at RF frequencies which otherwise may consume significant current and significantly reduce battery life. 
     The reference signal outputted by detector  40  is converted to a logic level by comparator U 1  and associated components R 3 , R 4 , and R 5  of amplifier  42 . The logic level reference signal is provided to pulse shaper  44 . D 2  of pulse shaper  44  removes noise from the output of the comparator and provides relatively clean pulses for analysis by processing circuitry  32 . D 2  allows a fast fall time of the detected RF signal and a slower rise time of a prescribed rate as set by R 6  and C 5  which also operates to provide a degree of noise reduction. 
     A table of values of an exemplary configuration of conditioning circuitry  30  configured for use with tag  20  comprising a parallel LC resonant circuit having a solenoid wire wound inductor of 9.7 uH and a capacitor of 39 pF is provided as Table A. Other components may be used in other configurations and/or for use with other configurations of tags  20 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE A 
               
               
                   
                   
               
               
                   
                   
                 Part 
               
               
                   
                 Component 
                 Name/Value 
               
               
                   
                   
               
             
            
               
                   
                 R1 
                 3K 
               
               
                   
                 R2 
                 150 
               
               
                   
                 R3 
                 2.4K 
               
               
                   
                 R4 
                 5.6M 
               
               
                   
                 R5 
                 10M 
               
               
                   
                 R6 
                 470K 
               
               
                   
                 C2 
                 1 pF 
               
               
                   
                 C3 
                 2 pF 
               
               
                   
                 C4 
                 1 pF 
               
               
                   
                 C5 
                 1000 pF 
               
               
                   
                 C6 
                 0.5 pF 
               
               
                   
                 L1 
                 100 uH 
               
               
                   
                 D1 
                 SMS7621 
               
               
                   
                 D2 
                 BAS70 
               
               
                   
                 U1 
                 LPV7215 
               
               
                   
                   
               
            
           
         
       
     
     Processing circuitry  32  is configured to receive reference signals outputted from pulse shaper  44  and is configured to process the reference signals to discriminate signals having a pattern or cadence corresponding to wireless communications of base communication device  12  from other signals resulting from the reception of electromagnetic energy provided by other sources apart from device  12 . Processing circuitry  32  may control the alarm circuitry  36  to generate a human perceptible alarm responsive to the discrimination indicating reception of wireless communications corresponding to base communication device  12 . 
     Processing circuitry  32  may use criteria in an attempt to discriminate received electromagnetic energy. The criteria may be predefined wherein, for example, the criteria is specified prior to reception of the wireless signals to be processed by remote communication device  14 . In one possible discrimination embodiment, processing circuitry  32  is configured to monitor for the presence of a plurality of identifiable components within the reference signals outputted by conditioning circuitry  30  and corresponding to communications of the remote communication device  14  with respect to base communication device  12  (e.g., the remote communication device  14  generates the identifiable components responsive to reception of the wireless signal emitted by the base communication device  12 ). In one embodiment, the processing circuitry  32  is configured to monitor for the presence of the identifiable components in the form of pulses. As described further below, processing circuitry  32  may attempt to match pulses of the reference signal being processed with a predefined pattern of the pulses in one implementation to discriminate communications from the base communication device  12  from interference. The processing circuitry  32  may control the alarm circuitry  36  to emit an alarm if criteria are met, such as identification of a plurality of identifiable components (e.g., pulses) and/or identification of the identifiable components in the form of a predefined pattern. The processing circuitry  32  may have to specify the reception of the identifiable components and/or pattern within a predefined time period in order to provide a positive identification of communications from base communication device  12 . One, more or all of the above exemplary criteria may be used in exemplary embodiments to discriminate signals from base communication device  12  from spurious electromagnetic energy received by the remote communication devices  14 . 
     More specifically, in one arrangement, processing circuitry  32  may access values for a plurality of parameters corresponding to the given configuration of the alarm system  10  (e.g., RF, AM, EM discussed above). The processing circuitry  32  may utilize the values of the parameters during monitoring of reference signals received from conditioning circuitry  30  and which specify time-amplitude criteria to discriminate communications from base communication device  12  from interference. The values of the parameters may define characteristics of the identifiable components (e.g., pulses) of the signal and to be identified. In a specific example, the parameters may additionally define a pattern of the identifiable components to be identified to indicate whether the communications are from base communication device  12 . The values of the parameters for the different types of systems may be predefined (e.g., defined before the generation of the reference signals to be processed) in one embodiment. For example, the values for the different configurations may be preprogrammed into the remote communication devices  14  prior to use of the devices in the field and the appropriate set of values may be selected corresponding to the type of alarm system  10  being utilized. 
     Exemplary parameters for the identifiable components and/or patterns of identifiable components may include minimum and maximum pulse width parameters, minimum and maximum pulse gap parameters, maximum valid pulse gap, number of pulses, and success count. The pulse width parameters are used to define the widths of the pulses to be monitored. The pulse gap parameters define the minimum and maximum length of time intermediate adjacent pulses, and the maximum valid pulse gap corresponds to a length of time wherein a timeout occurs if no additional pulse is received after a previous pulse. In one embodiment, the processing circuitry  32  may perform a moving window analysis wherein a given number of correct pulses defined by the success count parameter are attempted to be located within a moving window of pulses defined by the number of pulses parameter. Additional details regarding monitoring of identifiable components in the form of pulses with respect to a predefined pattern of the pulses are described with respect to  FIG. 5   
     Referring to  FIG. 5 , an exemplary method of processing of reference signals is shown according to one embodiment. The method may be performed in an attempt to discriminate electromagnetic energy generated by base communication device  12  and received by remote communication device  14  from electromagnetic energy resulting from other sources and received by remote communication device  14 . In one example, processing circuitry  32  is configured to perform the method, for example, by executing ordered instructions. Other methods are possible, including more, less and/or alternative steps. 
     At a step S 10 , all counters are reset. Exemplary counters include a pulse_cnt counter corresponding to a number of pulses counted and a success_cnt counter corresponding to a number of pulses counted which meet respective values of the parameters. 
     At a step S 12 , a width of a first pulse from pulse shaper circuitry is detected and measured. 
     At a step S 14 , a pulse gap after the first pulse is measured. 
     At a step S 16 , it is determined whether the gap measured in step S 14  exceeds a max_valid_gap parameter. This parameter may correspond to a timeout. If the condition is affirmative, the process returns to step S 10  wherein the counters are reset. If the condition is negative, the process proceeds to step S 18 . 
     At step S 18 , pulse timing of a plurality of pulses outputted from the pulse shaper circuitry may be performed. The determined pulse timing may be used to select one of a plurality of sets of values for parameters to be monitored. For example, different sets of values may be predefined and used for different configurations of alarm system  10 . In one embodiment, once the pulse timing is determined, the pulse timing may be used to select a respective appropriate set of values. Furthermore, at step S 18 , the pulse_cnt counter may be incremented corresponding to the pulse detected at step S 12 . 
     At a step S 20 , the width of the pulse detected at step S 12  and the following gap are calculated and compared to the set of values for the respective pulse width and gap parameters. If the measurements are negative in view of the parameter values, the process proceeds to a step S 24 . If the measurements are positive (e.g., matching) in view of the parameter values, the process proceeds to a step S 22 . 
     At step S 22 , the success_cnt counter is incremented indicating detection of a pulse within the values of the parameters. 
     At a step S 24 , the subsequent pulse width and gap is measured and the pulse_cnt counter is incremented. 
     At a step S 26 , the pulse gap is again compared to the max_valid_gap parameter. If the condition of step S 26  is affirmative, the process returns to step S 10  indicating a timeout. If the condition of step S 26  is negative, the process proceeds to a step S 28 . 
     At step S 28 , the measured pulse width and gap are compared with the selected values of the parameters. If the measurements are negative in view of the parameter values, the process proceeds to a step S 32 . If the measurements are positive in view of the parameter values, the process proceeds to a step S 30 . 
     At step S 30 , the success_cnt counter is incremented indicating detection of a pulse within the values of the parameters. 
     At a step S 32 , it is determined whether a desired number of pulses have been detected. In one example, the process waits until ten pulses have been detected. If the condition of step S 32  is negative, the process returns to step S 24 . If the condition of step S 32  is affirmative, the process proceeds to step S 34 . 
     At step S 34 , it is determined whether a desired number of successful pulses have been detected. In the above-described example monitoring ten pulses, the process at step S 34  may monitor a condition for the presence of at least five of the ten pulses meeting the criteria specified by the selected values. Other criteria may be used for steps S 32  and  34  in other embodiments. If the condition of step S 34  is negative, the process returns to step S 10  and no alarm is generated by remote communication device  14 . If the condition of step S 34  is affirmative, the process proceeds to step S 36 . 
     At step S 36 , the process has discriminated electromagnetic energy received via the remote communication device  14  as having been emitted from base communication device  12  from electromagnetic energy resulting from other sources. The discrimination indicates the presence of the remote communication device  14  in a secured area and the processing circuitry  32  can control the emission of an alarm signal. 
     At least some of the above-described exemplary embodiments provide an advantage of discrimination using the remote communication device  14  of communications of base communication device  12  from other spurious electromagnetic energy which may be emitted from other sources. Further, at least one embodiment of remote communication device  14  provides relatively very low signal strength signal detection, negligible impact to performance of tag  20  with respect to communications with base communication device  12 , and relatively low power consumption. 
     Further, the alarm system  10  may have improved discrimination in the presence of cellular and cordless telephones and other sources of interference which may otherwise preclude reliable detection of signals form base communication device  12  for example in an electronic article surveillance system. Accordingly, the alarm system  10  according to one embodiment may have reduced susceptibility to false alarms caused by interference. 
     Referring to  FIG. 6 , one possible embodiment of monitoring circuitry  50  which may be included in remote communication device  14  is shown. Monitoring circuitry  50  may be coupled with processing circuitry  32  in one implementation. Monitoring circuitry  50  is configured to reduce false alarms in some configurations due to the presence of spurious electromagnetic energy (e.g., electromagnetic energy not emitted by system  10 ) in the environment where system  10  is implemented. In one arrangement described below, monitoring circuitry  50  is configured to monitor for the presence of spurious electromagnetic energy and generate an output which may be utilized to reduce the presence of false alarms. 
     In one embodiment, monitoring circuitry  50  reduces false alarms which may exist with certain kinds of spurious electromagnetic interference. The illustrated configuration of monitoring circuitry  50  is arranged to monitor for interference which may have a similar characteristic (e.g., time signature) to wireless communications generated by base communication device  12  (e.g., the signature used to identify communications of device  12 ) and which may cause a false alarm by remote communication device  14 . For example, GSM phones transmit at substantially different frequencies of approximately 850-1900 MHz compared with one embodiment of wireless communications of system  10  at 8.2 MHz. However, transmitted signals of GSM phones may be sufficient to induce currents by radiation that trigger an embodiment of remote communication device  14 . The triggering may be due to a similarity of the GSM interference with a possible signature of the wireless communications of base communication device  12 . 
     In exemplary embodiments, monitoring circuitry  50  is tuned to a frequency of spurious electromagnetic energy (e.g., GSM interference) and is not tuned to the frequency band of wireless communications of base communication device  12 . For example, in the depicted embodiment, monitoring circuitry  50  is tuned to receive and demodulate spurious electromagnetic energy (e.g., a GSM phone transmission or other high frequency interference signal for example) outside of the frequency band of communications of base communication device  12 . In one embodiment, an antenna  52  of monitoring circuitry  50  may be tuned to a frequency band such as 100 MHz-5 GHz in configurations of alarm system  10  which use communications within a band of approximately 8.2 MHz. 
     An output node  54  of monitoring circuitry  50  may be coupled with processing circuitry  32 . Processing circuitry  32  may process signals received from output node  54  with respect to respective signals received from conditioning circuitry  30 . Processing circuitry  32  may analyze respective signals from circuitry  30 ,  50  which correspond to one another in time to determine whether output of conditioning circuitry  30  having an appropriate signature is responsive to communications of base communication device  12  or spurious electromagnetic energy. The output of monitoring circuitry  50  permits processing circuitry  32  to discriminate electrical signals received from conditioning circuitry  30  which result from communications of base communication device  12  from those which result from spurious electromagnetic energy in the illustrated configuration. As described further below, the processing circuitry  32  may perform the discrimination analysis based upon the output of monitoring circuitry  50 . 
     The above described embodiment is configured such that monitoring circuitry  50  detects possible sources of spurious electromagnetic energy which may impact the operations of alarm system  10  yet rejects proper communications of base communication device  12 . In an example implementation of alarm system  10  where spurious electromagnetic energy is present which may impact proper operation of alarm system  10 , both receivers of conditioning circuitry  32  and monitoring circuitry  50  may indicate the presence of a signal which resembles communications of base communication device  12  (e.g., having a signature corresponding to communications of base communication device  12 ) but results from the spurious electromagnetic energy. However, during communications of base communication device  12  within a proper frequency band (e.g., 8.2 MHz), only conditioning circuitry  30  generating electrical signals which indicate the presence of the communications of base communication device  12  are generated and while monitoring circuitry  50  does not. 
     If the output electrical signals of the receivers of conditioning circuitry  30  and monitoring circuitry  50  are both active at a respective moment in time and with a respective time signature which resembles communications of base communication device  12 , then the presence of spurious electromagnetic energy is indicated and processing circuitry  32  ignores the potential false alarm condition and does not control the generation of an alarm signal by alarm circuitry  36 . If however, the output electrical signal from monitoring circuitry  50  is inactive yet the output electrical signal from conditioning circuitry  30  at the respective moment in time is active with a valid signature, then a potential alarm condition is due to a legitimate communication from base communication device  12  and processing circuitry  32  may control alarm circuitry  36  to emit an alarm signal. Furthermore, if an output electrical signal of the monitoring circuitry  50  is active and the respective output electrical signal of the conditioning circuitry  30  is not active, processing circuitry  32  does not control the emission of an alarm signal in the described embodiment. 
     Antenna  52  may be implemented as a separate dedicated piece of wire serving as a monopole antenna tuned to a frequency range of spurious electromagnetic energy to be monitored in one configuration. Also, in the depicted embodiment of  FIG. 6 , monitoring circuitry  50  operates similarly to conditioning circuitry  30  wherein a coupling capacitor C 1  couples RF energy to a nonlinear detector diode D 1  while allowing for a DC shift so that the comparatively slow varying signal (e.g., generated from the envelope of a GSM cell phone or other unintentional source of interference) is allowed to develop across the diode D 1 . Non-linear element diode D 1  develops an electrical signal that is proportional to the envelope of the spurious electromagnetic energy. This electrical signal is coupled to holding capacitor C 2  by inductor L 1  which is an electrical short at low frequencies and open at higher frequencies so as to minimize loading of the antenna signal. The value of C 2  may be optimized for an expected timing sequence of spurious electromagnetic energy (if known or predictable). The values of C 1 , C 2 , and L 1  may be chosen in one embodiment such that communications of base communication device  12  are greatly attenuated yet the comparatively high frequency of spurious electromagnetic energy is optimized and detected. In the described embodiment, monitoring circuitry  50  is active responsive to spurious electromagnetic energy and is inactive or rejects communications of base communication device  12 . Therefore, the output electrical signal of monitoring circuitry  50  is only a representation of the spurious electromagnetic energy. The remaining components of monitoring circuitry  50  operate similarly to corresponding respective components of conditioning circuitry  30  in the depicted exemplary embodiment. 
     Due to the nature of unintentional injection of relatively very high frequencies (e.g., &gt;100 MHz) in some implementations, it may be more straightforward to develop monitoring circuitry  50  that receives relatively very high frequencies yet rejects relatively strong levels of comparatively low 8.2 MHz signals. In some embodiments, it may be more difficult to design a receiver of conditioning circuitry  30  which receives relatively low frequency 8.2 MHz and is not susceptible to the relatively high levels of spurious electromagnetic energy which may be present (e.g., radio frequency energy of a GSM phone). 
     Referring to  FIG. 7 , another possible configuration of conditioning circuitry  30  is shown including an alternate detector circuit which is less frequency selective when connected to a tag antenna (compared with the embodiment of  FIG. 4 ) and is accordingly slightly more sensitive to lower level signals. 
     Detector  40  includes D 1 , R 2 , C 4 , amplifier  42  includes comparator U 1 , and pulse shaper includes D 2  in the depicted arrangement of  FIG. 7 . The illustrated circuit provides sensitivity to signals from base communication device  12  in the milliVolt range while providing a detector  40  which is passive and consumes substantially no power from power source  38 . Other circuits are possible including more, less and/or alternative components. 
     During operation, output of tag  20  due to resonation with electromagnetic energy is detected by a non-linear device comprising diode D 1  in the depicted embodiment. More specifically, coupling capacitor C 2  connects signals generated by tag  20  to the detector  40  while allowing for a DC shift which becomes the output signal. Diode D 1  conducts in a forward biased direction when the RF signal received by tag  20  is negative thereby clamping the waveform to ground and is non-conducting when the RF signal is positive thereby developing a positive signal corresponding to the instantaneous value of the peak of the RF waveform (e.g., 8.2 MHz) generated by base communication device  12  for half of the wave cycle thereby providing a DC or slowly varying AC waveform that is proportional to the amplitude of the RF signal received by tag  20 . The inclusion of a non-linear element D 1  in the detector  40  improves the sensitivity of alarm device  22  of remote communication device  14 . In one embodiment, the described diode D 1  provides a non-linear relationship wherein current through diode D 1  is clamped to ground during the negative half cycle and allowed to swing positive during the positive half cycle of received voltage corresponding to input signals received from tag  20  and an output signal is provided to C 4  which is therefore proportional to the positive peak value of the received signal. The detected DC component signal is coupled by R 2  and AC filtered by R 2  and C 4 . C 4  holds the value of the detected voltage. Accordingly, in one embodiment, C 4  of detector  40  is configured to generate an envelope of the signal and generally resemble a square wave following the macro trend of the RF envelope of signals received from base communication device  12 . 
     The provision of detector  40  comprising a non-linear detector through the use of diode D 1  generates pulses having an absolute value relation to the signal received by the antenna circuit and applies the pulses to comparator U 1  in one embodiment. Detector  40  has a non-linear transfer characteristic in the described embodiment where the input and output of the detector  40  have an absolute value or logarithmic relationship through the use of diode D 1  in one embodiment. 
     The detector  40  described according to one embodiment provides increased sensitivity to wireless communications of base communication device  12  without the use of amplifiers operating at RF frequencies which otherwise may consume significant current and significantly reduce battery life. 
     The reference signal outputted by detector  40  is converted to a logic level by comparator U 1  and associated components R 3 , R 4 , and R 5  of amplifier  42 . The logic level reference signal is provided to pulse shaper  44 . D 2  of pulse shaper  44  removes noise from the output of the comparator and provides relatively clean pulses for analysis by processing circuitry  32 . D 2  allows a fast fall time of the detected RF signal and a slower rise time of a prescribed rate as set by R 6  and C 5  which also operates to provide a degree of noise reduction. 
     A table of values of an exemplary configuration of conditioning circuitry  30  configured for use with tag  20  comprising a parallel LC resonant circuit having a solenoid wire wound inductor of 9.7 uH and a capacitor of 39 pF is provided as Table B. Other components may be used in other configurations and/or for use with other configurations of tags  20 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE B 
               
               
                   
                   
               
               
                   
                   
                 Part 
               
               
                   
                 Component 
                 Name/Value 
               
               
                   
                   
               
             
            
               
                   
                 R1 
                 3K 
               
               
                   
                 R2 
                 100K 
               
               
                   
                 R3 
                 2.4K 
               
               
                   
                 R4 
                 5.6M 
               
               
                   
                 R5 
                 10M 
               
               
                   
                 R6 
                 470K 
               
               
                   
                 C2 
                 1 pF 
               
               
                   
                 C4 
                 1 pF 
               
               
                   
                 C5 
                 1000 pF 
               
               
                   
                 C6 
                 0.5 pF 
               
               
                   
                 D1 
                 SMS7621 
               
               
                   
                 D2 
                 BAS70 
               
               
                   
                 U1 
                 LPV7215 
               
               
                   
                   
               
            
           
         
       
     
     In compliance with the statute, the disclosure has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the disclosure is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents. 
     Further, aspects herein have been presented for guidance in construction and/or operation of illustrative embodiments of the disclosure. Applicant(s) hereof consider these described illustrative embodiments to also include, disclose and describe further inventive aspects in addition to those explicitly disclosed. For example, the additional inventive aspects may include less, more and/or alternative features than those described in the illustrative embodiments. In more specific examples, Applicants consider the disclosure to include, disclose and describe methods which include less, more and/or alternative steps than those methods explicitly disclosed as well as apparatus which includes less, more and/or alternative structure than the explicitly disclosed apparatus.