Patent Publication Number: US-7222712-B2

Title: Document validator with locking cassette

Description:
BACKGROUND OF THE INVENTION 
   This application is a continuation of provisional patent application No. 60/457,153 filed on Mar. 24, 2003. 

   FIELD OF THE INVENTION 
   The field of the invention relates to document recognition and more particularly to currency validators. 
   Currency validators are generally known. Such devices are typically used on such devices as vending machines or slot machines to accept a limited scope or type of bill of a particular currency or coupons or bar codes. 
   Currency validators typically function by measuring an amplitude of light reflection at one or more positions of the bill and comparing the measured color with a predetermined value. If the measured value falls within a range of the predetermined value, then the bill is accepted as genuine. If the measured value exceeds the predetermined value, then the bill is rejected. 
   Other currency validators rely upon fluorescence. Currency validators of this type are typically hand-operated devices that detect the use of specially formulated fluorescent inks used by some countries in the printing of their currency. 
   In the case of currency validation based upon fluorescence, an ultraviolet light is directed at the bill and a level of fluorescence is measured. If the level of fluorescence is below a predetermined value then the bill is accepted. 
   Other currency validators may rely upon a combination of color measurement and fluorescence. While such systems are relatively effective, they lack the flexibility to cope with currency that has been defaced or is in poor condition. Accordingly, a need exists for a currency validator that is able to recognize and reliably accept a wide variety of currencies and currency conditions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1   a–b  are top and side views of a document validator in accordance with an illustrated embodiment of the invention; 
       FIG. 2  is a cut-away view of the validator of  FIG. 1 ; 
       FIG. 3  is a plan view of the sensor arrays of the validator of  FIG. 1 ; 
       FIG. 4  depicts optical transmission paths of the sensor arrays of  FIG. 3 ; 
       FIG. 5  depicts optical profiles provided by the arrays of  FIG. 3 ; 
       FIG. 6  depicts a control system that may be used by the system of  FIG. 1 ; 
       FIG. 7  shows a simplified cut-away view of  FIG. 2 ; 
       FIG. 8  shows a section view of  FIG. 7 ; 
       FIG. 9  depicts a document stacking mechanism that may be used by the validator of  FIG. 1 ; 
       FIG. 10  depicts a locking assembly that may be used with the validator of  FIG. 1 ; and 
       FIG. 11  is a flow chart of the method steps that may be used by the validator of  FIG. 1 . 
   

   SUMMARY  
   A method and apparatus are provided for authenticating a document. The apparatus includes a profile processor adapted to collect a plurality of data profiles from a suspect document, a comparator adapted to compare the plurality of data profiles with a set of envelopes of a library document and to determine that the document is authentic when the plurality of profiles conforms with the plurality of envelopes and a push-in lock that locks a cassette that holds authenticated documents to a body of the apparatus for authenticating the document. 
   As used herein, measuring a metric of a suspect document means measuring a characteristic of the medium of the document. It does not mean measuring a width or thickness of the document. Further, measuring a characteristic of the medium of the document means measuring a characteristic of the substrate of the document or any substance printed thereon or any stamp, window or sticker permanently attached to the document. 
   Under one illustrated embodiment, the measured metric may be the reflected and transmissive qualities of the medium of the suspect document in response to an impinging infrared (IR), super red or blue optical signal. Under another illustrated embodiment of the invention, the measured metric may be the fluorescent signal emitted by the medium in response to an impinging ultraviolet (UV) signal. Under still another illustrated embodiment of the invention, the measured metric may be a magnetic level of the medium. 
   The measured metrics may be arranged into data profiles and compared with a corresponding set of envelopes of a library document to determine whether the suspect document is authentic. The envelopes may define upper and lower limits for the measured metrics of the suspect document. The determination of authenticity (also sometimes referred to herein as validating the document) may be based upon a comparison of the data profiles with a set of envelopes that define the library document and upon conformance of the data profiles with the set of envelopes. Conformance, in this case, means that the data profiles substantially lie between the upper and lower limits of the envelopes that define the library document. 
   The arrangement of the measured metrics into the data profiles may be based upon any method by which the distinctive features of a document may be captured. For example, under one embodiment the data profiles may be formed from data collected by signal format (e.g., magnetism of the medium, fluorescence of the medium, optical signal color and whether it is a reflected signal or a signal transmitted through the suspect document, etc.) and by position along a predetermined path across the document. 
   DETAILED DESCRIPTION OF AN ILLUSTRATED EMBODIMENT 
   The validator can be described as a system that identifies valid documents (e.g., currency) and functions to authorize some activity based upon the validation. For example, the validator may be used in a vending machine to accept currency and authorize the dispensing of food from the vending machine. As used herein, validation means determining that a document is authentic. 
     FIG. 1  depicts top and side views of a validator  10 , shown generally in accordance with an illustrated embodiment of the invention. The validator  10  includes a sensor section  12 , a transport system section  14  and a document cassette  16 . Documents may be fed into an entrance slot  18  where it is detected by a set of IR sensors  78   a,b . Detection by the IR sensors  78   a,b  activates the transport system. 
     FIG. 11  is a flow chart that depicts steps that may be followed by the validator  10  in determining the authenticity of a document. Reference may be made to  FIG. 6  as appropriate to an understanding of the invention. 
     FIG. 2  shows a cut-away side view of the validator  10 . The transport section  14  contains a drive system  20  that moves a document through the validator. The drive system  20  generally includes a drive motor  30  that is directly coupled to a gear train  32 . An output of the gear train  32  is directly coupled to a pair of head-end drive pulleys  34  mounted on a common shaft  36 . A pair of continuous belts  38 , equidistant from a centerline of a path of travel  50  of the document  46  and separated by a distance of at least 34 mm, pass over the head-end pulleys  34  and a set of tail-end pulleys  40 . A secondary pair of belts  42 , driven by the tail-end pulleys  40  drives a pair of initial drive capstans  44 . The drive system functions to transport a document  46  inserted into the slot  18  through the validator  10  along the note path  50 . 
   The transport system  20  moves the document  46  past a number of arrays of sensors within the sensor section  12 . The sensors function to detect  100  the presence of a document  46  as well as provide information sufficient to identify a type of document and to establish whether the document is authentic. Once the type of document has been identified and accepted as authentic, the transport system moves the document to an area adjacent a cassette  16 . A stacking system  48  functions to stack the document into the cassette. 
   The arrays of sensors may include a set of profiling sensor arrays, anti-stringing sensors, an ultraviolet (UV) sensor and a timing and position sensor. The profiling sensors include a magnetic sensor  54  that is centrally located adjacent a flat side of the document path  50  and a set of spaced-apart IR/blue sensor arrays  52  located on either side of the magnetic sensor  54  (one sensor array  52  shown in phantom in  FIG. 2 ). Following the IR/blue sensors  52  is a centrally-located super red/blue sensor array  56 . (As used herein, a super red optical signal is a visible optical signal adjacent the infrared spectrum). As each document passes through the profiling section of the validator  10 , a profile of the document  46  is collected  202  along the length of the document  46  based upon position by each sensor array. A profile of the document is a succession of readings of the same signal type along some predetermined path across a portion of the document. 
     FIG. 3  shows a plan view of the sensor  52 ,  54 ,  56 .  FIG. 4  shows a functional view of a IR/LED sensor array  52  in terms of optical transmission and detection. 
     FIG. 7  shows a simplified cut-away view of a left portion of the validator  10  of  FIG. 2 .  FIG. 8  shows a section view of the sensor section  12  of the validator  10  along lines  8 — 8 . 
   Each IR/blue sensor array  52  includes an IR light emitting diode (LED)  58  and a blue LED  60  ( FIG. 3 ). The array  52  also includes a first photodetector  62  on the same side of the document path as the IR LED  58  and blue LED  60  and located between the IR and blue LEDs  58 ,  60 . A second photodetector  64  is located on an opposing side of the document path opposite the first photosensor  62 . 
   A profile processing unit  108  of a control system  100  (shown in  FIG. 6 ) of the validator  10  alternately activates the IR LED  58  to generate an IR optical signal  66  and then the blue LED  60  to generate a blue optical signal  70 , each for a predetermined time period. During the time that the IR LED is activated, the processor  108  measures the IR signal detected by the first and second photodetectors  62 ,  64 . The first photodetector  62  measures a reflected IR signal  68 . The second photodetector  64  measures the transmitted signal  74  that passes through the document  46 . 
   After measuring the IR signal, the processor  108  deactivates the IR LED  58  and activates the blue LED  60  and repeats the measurements. As above, the first photodetector  62  measures a reflected blue signal  72 . The second photodetector  64  measures the attenuated signal  76  that passes through the document  46 . 
   Similarly, the processor  108  alternately activates the super red LED and blue LED of the super red/blue array  56 . The array  56  may have the same configuration and operate in substantially the same way as described with respect to  FIG. 4 . During the time that the super red LED is active, the processor  108  measures the reflected and transmitted super red energy on a first and second side of the document path. During the time that the blue LED is active, the processor  108  measures the reflected and transmitted blue energy on a first and second side of the document path. 
   As the transport system  20  moves the document  46  past the IR/blue sensor arrays  52  and the super red/blue sensor arrays  56 , the processor  108  collects data  202  as described above. The processor  108  also collects data from the magnetic sensor  54 . As the document moves past the arrays, a tachometer  104  measures a speed of the document past the arrays of sensors. By detecting the instant of entry of the document  46  into the validator  10  and knowing the speed of the document, the processor  102  may correlate each array and magnetic sensor reading to a position on the document. The data samples collected from each sensor may be concatenated together based upon the position on the document where it was collected to form the profile from that sensor and sensor array. 
     FIGS. 5   a–e  shows examples of data profiles that may be collected by the detectors  62 ,  64  of the IR/blue arrays  52  and super red/blue arrays  56 .  FIG. 5   a  shows an example of a profile of the reflected IR or super red energy measured by the detector  62  while  FIG. 5   c  shows an example of a profile of the transmitted IR or super red energy measured by the detector  64 .  FIG. 5   b  shows an example of a profile of the reflected blue energy measured by the detector  62  and  FIG. 5   d  shows an example a profile of the transmitted energy measured by the detector  64 . 
     FIG. 5   e  shows an example of a difference profile that may be generated by the processor  108 . The difference profile of  FIG. 5   e  may be generated by subtracting the measured blue energy at each point from the IR or super red energy of an adjacent point on the document  46 . 
   The profiles from the magnetic sensor  54 , IR/blue sensor arrays  52  and super red sensor array  56  together form a set of profiles that may be used to validate the document. The set of profiles obtained from each document is compared  204  with a set of respective profile envelopes for a valid document to determine the authenticity of the document. 
   For example, if a number of U.S. dollar bills were to be passed through the validator, the set of profiles for each dollar bill would be very similar, but not identical. The variations among the dollar bills at identical points defines a range of valid readings at that point. The range of valid readings along the length of the dollar bill can be concatenated to form an envelope for a valid dollar bill for each sensor type. The envelopes formed by each sensor for the dollar bill together form a library document defined by a set of envelopes that can be used to validate suspect dollar bills. 
   In addition, a library document can be created to validate a dollar bill no matter which way it is inserted into the validator. One set of envelopes may be created with Washington&#39;s image on the upper side facing to the right and another set of envelopes may be created with Washington facing the left (i.e., the bill turned end-for-end). A third and fourth set of envelopes may be created for the dollar bill with Washington&#39;s image facing downwards and inserted into the validator first one way and then turned end-for-end. 
   Further, a similar set of envelopes may be created for U.S. five dollar bills, ten dollar bills, fifties and one-hundreds. Similar sets of envelopes may also be created for foreign currencies or even coupons or redemption tickets. 
   Included within the validator may be a library of sets  110  of envelopes for valid documents (e.g., currency). Under one embodiment, the validator may contain a library for eleven different currency types in four different directions thereby providing a library of 44 library documents, each defined by a different sets of envelopes. 
   Included with each set of envelopes may be a commonly-used identifier of the associated library document (e.g., a U.S. one-dollar bill, eurodollar, etc.) As the validator reads and processes each document, a processor within the validator matches the set of profiles of each suspect document with sets of envelopes of the valid library documents within memory. Matching a profile with a corresponding envelope means determining that the measured metric falls within the upper and lower limits of the envelope. Where a match is found, the suspect document may be accepted as a validated member of the set of documents identified by the commonly-used identifier (e.g., a U.S. one dollar bill). 
   The matching of the set of profiles of the suspect document may be accomplished under a number of different methods. Under one method, one or two pilot profiles of the set of profiles may be selected and compared with respective envelopes within the library documents to give a first estimate of the best matches. The pilot profile(s) may be selected based upon experience in providing a first good indication of identity. 
   Once the best matches have been identified, a more rigorous comparison may be made between the remaining profiles of the suspect document and the remaining set of envelopes of the matched library documents. By using the pilot profile as a first level of matching, the processing time for validation can be considerably reduced. 
   Under another embodiment, each positional value of each profile may be successively compared with corresponding positional values of the sets of envelopes of the library documents. If the values of each profile of the suspect document falls within the ranges of each envelope of the set of envelopes of one particular library document, then the match is strong evidence that the suspect document is a valid member of that particular library document. 
   Alternatively, a percentage value may be formed for each of the profiles of the suspect document with corresponding envelopes of the library documents. The use of percentage values may be useful in the case of defaced currency or currency with foreign materials (e.g., mending tape, ink marks, etc.) disposed on the currency. 
   In this case, each value at each position of a profile may be compared with the range of values of a respective position and respective envelope of the valid documents and a percentage of matching points may be calculated within the processor  102 . The percentage match among the envelopes of the set of envelopes may be averaged to form an average percentage of match with each library document of the library. The library document with the greatest average percentage match to the suspect document may be selected as the set within which the suspect document most likely falls, subject to some minimum threshold value. 
   Alternatively, a curve matching routine may be used to match each profile of the suspect document with respective envelopes of the library documents. In this case, some mathematical or statistical formula (e.g., based upon standard deviation) may be used as evidence of a match. 
   As further evidence of authenticity, the UV sensor  26  may be used. In this case, it has been found that fluorescence of the document may be a counter indicator of authenticity. More to the point, prior art validators have relied upon a measurement of a level of fluorescence as an indicator of validity. The fluorescence may be provided by fluorescent inks that are used on some government-issued currencies. 
   However, it has been found that counterfeit documents often use paper that also provides a high level of fluorescence when subjected to UV. What has not been noted in the prior art is that valid documents fluoresce in a very narrow frequency range whereas counterfeit documents fluoresce over a relatively broad frequency range. To overcome this deficiency and provide an improvement over prior art methods, the validator described herein may use a bandpass filter  86  to suppress the fluorescence within the narrow range (in the yellow to green region) produced by valid documents. A threshold detector  106  may then by used by the processor  102  to detect fluorescence that exceeds a threshold value outside that range as a means of identifying invalid documents. 
   The validation of a suspect document may be based on a combination of profile processing and UV sensing. UV sensing may involve the use of an absolute threshold or a variable threshold that depends upon a position of a reading on the document or in a fluorescent profile. The final determination of authenticity may be based on a set of threshold values in the profiles processed and also upon a set of weights assigned by a weighting processor  112 . For example, the threshold for at least some of the profiles processed may be set such that the profiles of the suspect document must fall within the respective envelope of the set of envelopes of a library document and be given a higher weighting factor. Alternatively, the threshold for other profiles processed may be set at some lower value to accommodate some level of defacing of the document and be given a lower weighting factor. Similarly, the UV threshold may be set at some constant level or adjusted upwards or downwards to accommodate environmental factors (e.g., sunlight entering the slot  18 ). In any case, once the suspect document has been found to be within the thresholds and the sum of the weights exceed some weighting threshold, the suspect document  46  may be accepted as having been validated. 
   Once a document has been validated, the environment of the document between arrays  52  and  56  may be examined to verify that there are no strings attached. As is known, prior art bill validators may be defeated by attaching strings to bills and using the string to pull the bill out of the validator once the bill has been accepted. 
   In this case, an adjustable IR transmitter  28   a  and receiver  28   b  may be used to detect the presence of tape or strings. The transmitter and receiver  28  may be arranged to operate parallel with a predominant plane of the document and to transmit the detection signal through the path  50  of the document  46 . A threshold value may be used to avoid false readings due to environmental factors (e.g., sunlight). Acception or rejection may occur based upon the above criteria and upon the processor  102  detecting a signal from the receiver  28   b  (indicated that there are no strings attached) after the document  46  has reached the cassette. 
   Once the document  46  has been authenticated and it has been determined that no strings are attached, then the validator  10  may transmit notification of receipt and acceptance of the document using the commonly accepted terminology of the matching library document. Notification of validation may be sent by operation of the interface module  22  (discussed in more detail below). The validator  10  may also then insert (i.e., stack) the document into the cassette  16 . 
   To determine a timing of the stacking cycle, an IR transmitter  27   a  and receiver  27   b , located on a first side of the document path may be used in conjunction with a light pipe  25  disposed on an opposite side of the document path. The transmitter and receiver transceive an optical signal perpendicular to a predominant plane of the document  46 . 
   The difficulty in the prior art of determining document position above the cassette  16  has been the presence of transparent windows in some foreign currencies (e.g., Australian). The transmitter  27   a  solves this problem by transmitting an optical signal through one portion of the document path  50  and the detector  27   b  detects the signal transmitted through a different portion of the document path  50 . A light pipe on an opposite side of the document path transfers light from the transmitter  27   a  location laterally to the receiver  27   b  location. 
   Further, the light pipe is embedded in the cassette. Embedding the light pipe in the cassette allows the light pipe to also function as a detector for the presence of the cassette. 
   The document path of the validator is designed for documents up to 72 mm wide and approximately 160 mm long. However, many documents are much narrower than 72 mm. In order to transport documents from an entrance of the validator to the cassette, the pairs of rollers  44  and belts  38  are provided that are placed approximately 16–18 mm from the edges. 
   Upon insertion of a document, the pair of roller  44  initially engage and transport the document past the magnetic, IR/blue and super red/blue sensors. After the document passes the super red/blue sensor, the document engages the pair of belts  38  where it is transported past the UV sensor and to the area above the cassette and below the stacking plate  49 . 
   As the document  46  reaches the area above the cassette, the position detector  29  sends a signal to the processor  102 . The processor  102 , in turn, activates the stacking motor and gear box  31  that, through the use of an drive pin  80  and scissors assembly  80  cause the stacking plate  49  to extend and retract. 
   By operation of the stacking motor  31  and scissors assembly  80 , the stacking plate  49  pushes the document into the cassette through an aperture  86  on the upper surface of the cassette. Within the cassette, a carrier plate  82  and spring  84  function to receive the document  46  and via operation of the spring  84  cause the accumulated documents to assume a stacked format. 
   The stacking plate  49  occupies the area above the path  50  between the belts and is, therefore, much narrower than the document. As used herein, pushing or plunging the document into the cassette means pushing the document (perpendicular to the predominant plane of the document) through the aperture in an upper surface of the cassette where the aperture has a peripheral distance that is less than that of the document. As used herein, the predominant plane of the suspect document means that plane of the document defined by the thickness of the document or, stated differently, the predominant plane of the document lies parallel to and within the thickness of the document. 
   For example, the cassette may have an aperture that is approximately 160 mm long and a width of approximately 45 mm. As such, the peripheral distance of the aperture is approximately 410 mm. 
   In order to ensure the perpendicular translation of the predominant plane of the document from the document transport path into the cassette without lateral movement, the stacking plate may be provided with an anti-slip surface. Under one embodiment, the anti-slip surface may be obtained by disposing an area of silicone-rubber on opposing ends of the stacking plate. Under one embodiment, the area of silicon-rubber may be provided in the form of a number of silicon-rubber bumps disposed within a series of apertures (e.g., 5) proximate each end of the stacking plate. The silicon-rubber bumps may be provided by injecting the silicone-rubber into the apertures in such a way that the silicone-rubber extends above an active surface of the stacking plate by an appropriate distance (e.g., 1 mm). 
   Under one embodiment, the cassette has sufficient depth to accept up to 250 documents. Under other embodiments, the cassette may have sufficient depth to accept 600 or 1,000 documents. 
   The cassette may be provided with a pair of outwardly extending support pins on each side of the cassette. The validator may be provided with a complementary set of locking channels to accept the cassette. Locking of the cassette to the validator body may occur by lateral movement of the cassette parallel to the document path that lies immediately above the cassette. 
   The cassette may also be provided with an optional push lock  88  ( FIG. 10 ) secured by a set of screws inserted from inside the validator stacking chamber to prevent removal of the cassette from the validator. The push lock may be of value in allowing a progressive level of security provided within a device relying upon the validator. For example, in vending machines, one level of personnel is allowed access to the interior of the vending machine for filling and servicing the machine while another level of personnel is allowed access for emptying the cassette. Because of the trusted level of any personnel allowed within the device, the push lock does not need the mechanical strength that would be otherwise required of an external lock. More specifically, the purpose of the push lock is not to provide mechanical resistance to force, but to provide a locking mechanism that cannot be easily defeated without leaving physical evidence of tampering. 
   The push lock differs from the prior art in that the push lock is not related to the standard cam lock of the prior art. In contrast, the push lock of the validator simply mounts to the validator body and is provided with an movable cylinder that may be pushed in the direction of key insertion to a locking position. The pushing of the cylinder advances a connected peg into the locking channel behind the pins of the cassette to prevent removal of the cassette from the validator. 
   In order to accommodate a variety of interface requirements of the environments where the validator is used, a replaceable interface module  22  ( FIG. 2 ) may be provided for the validator. The interface module  22  may be mounted inside the validator  10  behind an easily removable face plate  24 . The interface module may be used to accommodate a variety of voltages from external sources that supply power to the validator and also a variety of interface data formats that may be required by systems that rely upon the document validator. For example, the validator may be used in gaming machines (e.g., slot machines), vending machines or entry control devices (e.g., ticket validating devices for a concert or movie). In the case of a slot machine or entry control devices, a power supply voltage may be 12 volts, while for a vending machine, the supply voltage may be 24–42 volts. Further, a slot machine may require a data interface in the form of a USB connection while a vending machine may require a multi-drop bus (MDB) interface. 
   To accommodate the interface environment, the interface module may be provided as a printed circuit board (PCB) with a five pin receptacle on one end and a six pin receptacle on an opposing end. An opposing male portion of the five and six pin connectors may be provided on a main circuit board of the validator. The opposing male portions provide structural support for the interface module and provide a mechanism for easily replacing the module with another module adapted to accommodate a new operating environment. 
   Signal and power connections may be intermixed within the five and six pin connectors. Alternatively, the five pin connector may be used for supplying power to the validator while the six pin connector may be used to provide a data interface requirements. An external sixteen-pin male connector  33  may be provided on an external surface of the validator to receive power from the external source and provide data to connected devices. Predefined pins on the external connector and five and/or six pin connector may be dedicated to supplying power to the validator. Similarly, predefined pins on the external connector and five and/or six pin connector may be dedicated to the data interface format required for external devices to communicate with the validator. 
   In the case where the validator is to be installed in a vending machine with a 24–42 volt power supply and an MDB data exchange format, at least a first portion of the interface module would be dedicated to a power supply that would accept the 24–42 volts as an input and to reduce the 24–42 volts to a voltage useable by the validator (e.g., using a switching power supply). Similarly, a second portion of the interface module would be devoted to a set of drivers that allow the external device to communicate with the validator using the MDB format. 
   Alternatively, where the validator is to be installed into a local area network (LAN), then the first portion of the interface modules dedicated to supplying power to the validator may be much simpler and, in fact, may simply be a set of connecting links if the external source provides power at the same voltage as that required by the validator. The second portion of interface module, however, may be somewhat more complicated. 
   Alternatively, the validator may be interconnected with external devices using a USB connector. In this case, the second portion of the interface module may require a USB processor to allow the validator to register and exchange data with connected devices under the USB format. Further, an external connector in the form of a USB connector may also be needed in place of (or in addition to) the 16-pin connector. 
   In this case the USB processor may be programmed to accept and/or transmit formatted self-descriptive information packets or HID report descriptors as described in “The Device Class Definition for Human Interface Devices, Firmware Specification”, Version 1.0—Final, USB Implementers Forum, 1997. An interpretive software module within a host computer of any connected device contains and/or uses a library of pre-defined peripheral device archtypes, data structure building rules and signal handling protocols. 
   The use of the USB processor allows validators  10  to be installed within other devices (e.g., slot machines) at will without the necessity of activating any software routines to install the validator  10  on the host. In this case, the validator  10  (through the USB processor and interface) automatically registers with the host upon startup and may periodically transfer status messages to the host. Further, the use of the USB interface allows a game system architect to obviate the need for a communications hub and a microcontroller to service each validator  10 . 
   In another embodiment of the invention, the validator is provided with a reset function that avoid false resets based on careless handling of the validator when activated. In order to avoid false resets, the validator provides a time delay associated with the reset button  90 . In order to activate the reset button, a user may be required to press and hold the reset button in a depressed state for a predetermined time period (e.g., 4 seconds) before a reset may be executed. 
   A specific embodiment of a document validator has been described for the purpose of illustrating the manner in which the invention is made and used. It should be understood that the implementation of other variations and modifications of the invention and its various aspects will be apparent to one skilled in the art, and that the invention is not limited by the specific embodiments described. Therefore, it is contemplated to cover the present invention and any and all modifications, variations, or equivalents that fall within the true spirit and scope of the basic underlying principles disclosed and claimed herein.