Patent Publication Number: US-2002008140-A1

Title: Method and apparatus to perform a predefined search on data carriers, such as RFID tags

Description:
TECHNICAL FIELD  
       [0001] This application relates to methods and apparatus for reading data carriers such as machine-readable symbols (e.g., barcode symbols, area and/or matrix code symbols) and wireless memory devices (e.g., RFID tags).  
       BACKGROUND OF THE INVENTION  
       [0002] A variety of methods exist for tracking and providing information about items. For example, inventory items typically carry printed labels providing information such as serial numbers, price, weight, and size. Some labels include data carriers in the form of machine-readable symbols that can be selected from a variety of machine-readable symbologies, such as bar code, and/or area or matrix code symbologies. The amount of information that the symbols can contain is limited by the space constraints of the label. Updating the information in these machine-readable symbols typically requires the printing of a new label to replace the old label.  
       [0003] Data carriers such as memory devices provide an alternative method for tracking and providing information about items. Memory devices permit the linking of large amounts of data with an object or item. Memory devices typically include a memory and logic in the form of an integrated circuit (“IC”) and means for transmitting data to and/or from the device. For example, a radio frequency identification (“RFID”) tag typically includes a memory for storing data, an antenna, an RF transmitter, and/or an RF receiver to transmit data, and logic for controlling the various components of the memory device. RFID tags are generally formed on a substrate and can include, for example, analog RF circuits and digital logic and memory circuits. The RFID tags can also include a number of discrete components, such as capacitors, transistors, and diodes.  
       [0004] RFID tags can be passive, active or hybrid devices. Active devices are self-powered, by a battery for example. Passive devices do not contain a discrete power source, but derive their energy from an RF signal used to interrogate the RFID tag. Passive RFID tags usually include an analog circuit that detects and decodes the interrogating RF signal and that provides power from the RF field to a digital circuit in the tag. The digital circuit generally executes all of the data functions of the RFID tag, such as retrieving stored data from memory and causing the analog circuit to modulate the RF signal to transmit the retrieved data. In addition to retrieving and transmitting data previously stored in the memory, the RFID tag can permit new or additional information to be stored in the RFIL) tag&#39;s memory, or can permit the RFID tag to manipulate data or perform some additional functions. RFID tags are available from a number of manufacturers, including Texas Instruments, Dallas, Tex., and Omron of Japan.  
       [0005] Another form of memory device is an optical tag. Optical tags are similar in many respects to RFID tags, but rely on an optical signal to transmit data to and/or from the tag.  
       [0006] Additionally, touch memory data carriers are available, for example touch memory devices from Dallas Semiconductor of Dallas, Texas. Touch memory devices are similar to RFID tags but require physical contact with to store and retrieve data.  
       [0007] A user typically secures a data carrier to an item, such as a good, product, or container by way of a pressure sensitive adhesive. The data carrier often encodes information specifically relating to the item such as identifying or destination information. An individual, such as a checkout or inventory clerk, can retrieve data about any given item, for example, by scanning the machine-readable symbol or interrogating the RF tag, optical tag, or touch memory device. Access to the data can be useful at the point of sale, during inventory, during transportation, or at other points in the manufacture, distribution, sale, or use of the tagged item.  
       [0008] Relatively high cost is one of the drawbacks of memory devices, thus, many applications rely on the less expensive printed machine-readable symbols. Another significant drawback is the difficulty of identifying a particular memory device from a group of memory devices. It is particularly difficult to associate the information read from the RFID tag with a physical item or container. The ability to read data from different types of data carriers, for example machine-readable symbols and RFID tags, and/or to associate and manipulate such data can provide numerous benefits in the automatic data collection (“ADC”) industry.  
       SUMMARY OF THE INVENTION  
       [0009] In one aspect a data carrier reader includes an RFID tag reading section and a machine-readable symbol reading section, which can contain some common components. The reader is operable in an RFID tag reading mode and/or a symbol reading mode. The reader provides a consistent and intuitive user interface within, and between, the operating modes. The user interface can include visual, aural and tactile indicators. The visual indicators can include a pattern displayed by indicators on the reader, or projected onto or near the data carrier.  
       [0010] In another aspect, a data carrier reader is capable of executing a number of different reading methods. A method for reading single RFID tags can store read data to a buffer for eventual transmission to a host, and can suppress redundant data. Another method identifies all RFID tags having a characteristic data string that appears on a list. In contrast, another method identifies any RFID tags having a characteristic data string that does not appear on the list. Still another method associates data read from an RFID tag with a particular object or item using a data coded in a machine-readable symbol. In a further method, the machine-readable symbol is automatically read when the RFID tag is within a predetermined proximity of the reader. In each method, a consistent and intuitive output can be provided to the user to identify the successful and unsuccessful operations such as reading an RFID tag or machine-readable symbol. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, various elements may be arbitrarily enlarged and positioned to improve drawing legibility.  
     [0012]FIG. 1 is a partial block diagram, partial front elevational view of a facility including a data carrier reader reading data carriers carried by a number of items, the reader communicate with a host through an interface.  
     [0013]FIG. 2 is a functional block diagram of the reader according to one embodiment of the invention.  
     [0014]FIG. 3 is a top plan view of the reader of FIG. 2.  
     [0015]FIG. 4 is a partial top plan view of an alternative set of visual indicators for the reader of FIG. 2.  
     [0016] FIGS.  5 A- 5 C together form a chart of selected input and output signals for operating the reader of FIG. 2 and the visual indicators of FIG. 4.  
     [0017]FIG. 6 is a top plan view of a graphic display of the reader of FIG. 3.  
     [0018]FIG. 7 is a top plan view of an alpha-numeric display of the reader of FIG. 3.  
     [0019]FIG. 8 is a flowchart showing a method of reading single RFID tags.  
     [0020]FIG. 9 is a flowchart showing a method of determining when a reader is finished reading RFID tags.  
     [0021]FIG. 10 is a flowchart showing a method of reading multiple RFID tags.  
     [0022]FIG. 11 is a flowchart showing a method of performing an inclusive search of RFID tags.  
     [0023]FIG. 12 is a flowchart showing a method of performing an exclusive search of RFID tags.  
     [0024]FIG. 13 is a flowchart showing a method of associating data from an RFID tag with an item using a machine-readable symbol.  
     [0025]FIG. 14 is a flowchart showing a method of automatically imaging a machine-readable symbol based on proximity to an RFID tag to associate data from an RFID tag with an item using the machine-readable symbol.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0026] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures associated with RFID tags, RFID tag readers, one- and two-dimensional symbologies, symbol readers, microprocessors and communication networks have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments of the invention.  
     [0027] The headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.  
     Data Carrier Reader  
     [0028]FIG. 1 shows a data carrier reader  10  reading one or more of a number of data carriers, such as the RFID tags  12  on the containers or items  14 . The reader  10  includes a head  16 , a handle  18  and a trigger  20 . An interface  22  can couple the reader  10  to a host  23 , such as a centralized computer, as described in detail below.  
     [0029] The tags  12  can take the form of an RFID tag  12 A that carries a machine-readable symbol  24 A on a visible surface of the tag. Alternatively, the tags  12  can take the form of a separate RFID tag  12 B and machine-readable symbol  24 B. The separate RFID tag  12 B and machine-readable symbol  24 B can be physically associated, for example, securing each to the same physical object, such as the item  14 . The RFID tag  12 A,  12 B and machine-readable symbol  24 A,  24 B can contain logically associated information, for example information related to the item  14  to which the tags  12  are secured, such as identifying and/or shipping information.  
     [0030] As shown in FIG. 2, the reader  10  contains an RFID tag reading section  30 , a symbol reading section  32 , a user input section  34 , a user output section  36 , and a communications section  38  all coupled by a bus  40 . The bus  40  provides data, commands and/or power to the various sections  30 - 38 . The reader  10  can include an internal power source such as a rechargeable battery (not shown) or can receive power from an external power source such as a wall outlet by way of an electrical cord (not shown). Each of these sections  30 - 38  will be described individually below, although in the illustrated embodiment some of these sections share common components.  
     RFID Tag Reading Section  
     [0031]FIG. 2 shows the RFID tag reading section  30  of the data carrier reader  10  including an antenna  42  coupled to a radio  44 . The radio  44  is coupled via the bus  40  to a microprocessor  46  and a random access memory (“RAM”)  48 . The RAM  48  can include a characteristic data string buffer  49  to temporarily store characteristic data strings, as will be explained in detail below. Alternatively, the reader  10  can include a discrete characteristic data string buffer (not shown). While FIG. 2 shows a single microprocessor  46 , the data carrier reader  10  may include separate dedicated processors for each of the RFID tag and symbol reading sections  30 ,  32 .  
     [0032] While a dipole antenna  42  is shown, the data carrier reader  10  can employ other antenna designs. Of course, the antenna can be selected to achieve a particular focus, for example, a highly directional antenna can enhance the ability of the reader  10  to select a single RFID tag  12  out of a group of RFID tags. The radio  44  can take the form of a transceiver capable of transmitting and receiving at one or more of the frequencies commonly associated with RFID tags  12  (e.g., 350 kilohertz, 400 kilohertz, 900 kilohertz). While these frequencies typically fall within the radio frequency range of the electromagnetic spectrum, the radio  44  can successfully employ frequencies in other portions of the spectrum. Antenna design and radios are generally discussed in  The ARRL Handbook for Radio Amateurs,  76 th  Ed., American Radio Relay League, Newington, Conn., U.S.A. (1999) (ISBN: 0-87259-181-6), and commonly assigned patent application U.S. Ser. No. 09/280,287, filed Mar. 29, 1999, entitled ANTENNA STRUCTURES FOR WIRELESS COMMUNICATIONS DEVICE, SUCH AS RFID TAG (Atty. Docket No. 480062.648).  
     [0033] A read only memory (“ROM”)  50  stores instructions for execution by the microprocessor  46  to operate the radio  44 . As used in this herein, ROM includes any non-volatile memory, including erasable memories such as EEPROMs. The programmed microprocessor  46  can control the radio  44  to emit an interrogation signal, including any required polling codes or encryption, and to receive a return signal from an RFID tag  12 A,  12 B. The programmed microprocessor  46 , RAM  48 , radio  44  and antenna  42  thus form the RFID reading section  30 .  
     Symbol Reading Section  
     [0034]FIG. 2 also shows the symbol reading section  32  of the data carrier reader  10  including an image sensor  52  and an illumination source, such as the laser  53 . The image sensor  52  can take the form of a one- or two-dimensional charge coupled device (“CCD”) array. Alternatively, the reader  10  can employ other known imaging devices, for example laser scanners or Vidicons. In certain embodiments, the data carrier reader  10  can omit the illumination source, for example where the image sensor  52  is a two-dimensional CCD array operable with ambient light. Alternatively, the data carrier reader  10  can rely on other illumination sources, such as light emitting diodes (“LEDs”) or a strobe light, that can be positioned to illuminate a desired one of the machine-readable symbols  24 A,  24 B. The reader  10  can employ suitable optics such as lens and mirrors (not shown) for directing light reflected from the machine-readable symbol  24 A,  24 B to the image sensor  52 .  
     [0035] The reader  10  includes an analog-to-digital (“A/D”) converter  54 , to transform the analog electrical signals from the image sensor  52  into digital signals for use by the microprocessor  46 . The bus  40  couples the image data from the A/D converter  54  to the microprocessor  46  and the RAM  48 . A portion of the RAM  48  can form an image buffer  56  for temporarily storing data, such as a captured image data from the image sensor  52 . The ROM  50  contains instructions for the microprocessor  46 , that permit the microprocessor  46  to control the image sensor  52  to capture image data and to decode and/or manipulate the captured image data. The programmed microprocessor  46 , RAM  48 , image sensor  52 , and A/D converter  54 , thus form the symbol reading section  32 .  
     [0036] Symbol reading and decoding technology is well-known in the art and will not be discussed in further detail. Many alternatives for image sensors, symbol decoders, and optical elements that can be used in the reader  10  are taught in the book,  The Bar Code Book,  Third Edition, by Roger C. Palmer, Helmers Publishing, Inc., Peterborough, N.H. U.S.A. (1995) (ISBN 0-911261-09-5).  
     Communications Section  
     [0037] The communications section  38  includes a communications buffer  47  and a communications port  49 . The communications buffer  47  can temporarily store incoming and outgoing data and/or commands where the communications speed of the reader  10  does not match the communications speed of some external device, such as the interface  22  (FIG. 1). The communications port  49  provides communications between the reader and external devices. While shown as a hardwire connection to the interface  22  (FIG. 1), the communications port can be a wireless interface, and can even employ the antenna  42  and radio  44  of the RFID tag reading section  30 . Additionally, the reader  10  can include the interface  22  as an integral part of the reader  10 .  
     [0038] The interface  22  (FIG. 1) can provide communications over a communications network  68  to the host  23 , allowing transmissions of data and/or commands between the reader  10  and the host  23 . The communications network  68  can take the form of a wired network, for example a local area network (“LAN”) (e.g., Ethernet, Token Ring), a wide area network (“WAN”), the Internet, or the World Wide Web (“WWW”). Alternatively or additionally, the communications network  68  can be a wireless network, for example, employing infrared (“IR”), satellite, and/or radio frequency (“RF”) communications.  
     [0039] The host  23  can receive from each of a number of the readers  10 , data collected from the RFID tags  12  and machine-readable symbols  24 . The host  23  can use the data with a database, and can automatically manipulate the data, for example to automatically performing inventory or to track shipments.  
     [0040] The host  23  can provide data and commands to each of a number of the readers  10 . For example, the host can share data between the readers  10 , such as providing a list of either located or missing identifiers, as will be discussed in more detail below in reference to inclusive and exclusive searches. The host  23  can provide a command to toggle the reader  10  between an RFID tag reading mode and a symbol reading mode, which is described below in further detail. Thus, the host  23  can command, coordinate and share data between a number of readers  10 . Commonly assigned patent application U.S. Ser. No. 09/, filed, 1999, entitled, “SYSTEM AND METHOD FOR AUTOMATICALLY CONTROLLING OR CONFIGURING A DEVICE, SUCH AS AN RFID READER” (Atty. Docket No. 480062.672) contains teachings that can be used to automatically control or configure the reader  10 .  
     User Input Section  
     [0041] The user input section  34  includes the trigger  20 , the mode switch  34 , and can include a user input device  58 . The bus  40  couples the mode switch  34  to the microprocessor  46 . In response to selection of the mode switch  34 , the microprocessor  46  switches between the symbol reading mode and the RFID tag reading mode, for example by toggling between the two operating modes. The reader  10  can employ additional operating modes, or switching positions as desired, for example a switch position that places the reader  10  in an OFF state or a WAIT state to conserve energy.  
     [0042] In the symbol reading mode, the microprocessor  46  operates the image sensor  52  to image one of the machine-readable symbols  24 A,  24 B. The microprocessor  46  decodes the imaged symbol to retrieve the data encoded in the machine-readable symbol  24 A,  24 B, such as a respective identifier. In the RFID tag reading mode, the microprocessor  46  operates the radio  44  to emit an interrogation signal and to receive a response from one or more of the RFID tags  12 A,  12 B to the interrogation signal. The microprocessor  46  decodes the response signal to retrieve the data encoded in the RFID tag  12 A,  12 B, such as a respective identifier.  
     [0043] The mode switch  34  can be a membrane switch, mounted to the exterior of the reader  10  for easy selection by the user. The mode switch  34  can additionally, or alternatively, be implemented in the software to supplement or replace the user selectable mode switch on the exterior of the reader  10 . The software implemented switch is particularly useful where the host  23  (FIG. 1) controls the operating mode of the reader  10 . Alternatively, the mode switch  34  can be implemented as an icon on a touch sensitive display  74 . In further alternatives, the trigger  20  can function as the mode switch  37 . In one instance, the number of successive trigger pulls or activations can determine the operating mode. For example, two successive trigger pulls can select the symbol mode, while three successive trigger pulls selects the RFID mode; or a single trigger pull can cause the reader  10  to read a symbol while a double trigger pull toggles between the symbol and RFID modes. Alternatively, the duration of trigger activation can determine the operating mode. For example, a trigger pull of under 0.5 seconds can select the symbol mode, while a trigger pull of longer than 0.5 seconds can select the RFID mode; or a trigger pull of under 0.5 seconds can cause the reader  10  to read a symbol while a trigger pull of over 0.5 seconds toggles the reader between the symbol and RFID modes. Additionally, or alternatively, the mode switch can be context sensitive, switching modes based on data read from a previously read data carrier  12 A,  12 B,  24 A,  24 B. For example, a previously read RFID tag  12 A can indicate the existence of a symbol  24 A. In response, the data carrier reader  10  can automatically switch into symbol mode and read the symbol  24 A associated with the RFID tag  12 A.  
     [0044] The bus  40  also couples the trigger  20  to the microprocessor  46 . In response to activation of the trigger  20 , the microprocessor  46  can cause the image sensor  52  to image one of the machine-readable symbols  24 A,  24 B when the reader  10  is operating in the symbol reading mode. In at least one embodiment, the microprocessor  46  can also cause the radio  44  and antenna  42  to emit an interrogation signal in response to the activation of the trigger  20  while in the reader  10  is operating in the RFID tag reading mode.  
     [0045] The user input device  58  can take the form of a keypad  60  (FIG. 3), mouse, touch screen and/or other user operable device to input information and/or commands to the reader  10 . The bus  40  couples the user input device  58  to the microprocessor  46 , to allow the user to enter data and commands.  
     User Output Section  
     [0046] The user output section  36  includes human-perceptible visual and audio indicators  62 ,  64  respectively. The bus  40  couples the visual and audio indicators  62 ,  64  to the microprocessor  46  for control thereby. The visual indicators  62  can take a variety of forms, for example: light emitting diodes (“LEDs”); a graphic display such as a liquid crystal display (“LCD”), and/or an alpha-numeric display such as a 7-segment display. The audio indicator  64  can take the form of one or more dynamic, electrostatic or piezo-electric speakers  66 . The speaker  66  is operable to produce a variety of sounds (e.g., Clicks and Beeps), and/or frequencies (e.g., tones), and to operate at different volumes. The reader  10  can also include tactile indicators such as a vibrating member. The specific operation of the user output section  36  is discussed in more detail below.  
     [0047]FIG. 3 shows a portion of the user interface located on the head  16  of the reader  10 . The user interface includes the elements of the user input section  34 , such as the trigger  20 , the mode switch  34  and the keypad  60 . The user interface also includes the elements of the user output section  36  including the visual indicators  63  and the speaker  66 . In particular, the visual indicators  62  in the illustrated embodiment include a set of RFID related LEDs  70 , a set of machine-readable symbol related LEDs  72 , and a display  74 .  
     [0048] The data carrier reader  10  can additionally, or alternatively, employ the laser  53  as the visual indicator. The laser can be successively pulsed or flashed according to a set of predefined human-recognizable temporal patterns to provide information to the user, such as user indications corresponding to the various reader operations and/or the responses from the date carriers  12 A,  12 B,  24 A,  24 B. Employing the laser  53  as a portion of the user interface provides a number of distinct benefits. For example, operating the laser  53  to provide human-recognizable patterns can eliminate the need for other visual indicators  62 . The data carrier reader  10  can employ multiple illumination sources such as lasers  53  or LEDs of different colors, or an illumination source capable of producing a number of different colors to provide the appropriate user indications, as set out in FIGS.  5 A- 5 C. As discussed in detail below, the human-recognizable patterns can take the form of a predefined sequence of laser flashes of one or more colors, separated by time (i.e., temporal pattern).  
     [0049] The visual and audio indicators  62 ,  64  are configured to provide an intuitive user interface consistent across the RFID tag and symbol reading modes. For example, the RFID tag related and symbol related LED sets  70 ,  72  each contain green  76 ,  78 , yellow  80 ,  82  and red  84 ,  86  LEDs, in an order or pattern that is consistent between the sets. The particular LED  76 - 86 , as well as the number and/or pattern of flashes, is set such that the same color LEDs flash the same pattern for analogous RF tag reading and symbol reading activities. For example, the yellow LED  80  in the RFID tag related set  70  flashes during the reading of one of the RFID tags  12 A,  12 B (FIG. 1), while the yellow LED  82  in the machine-readable symbol related set  72  flashes during the reading of one of the machine-readable symbols  24 A,  24 B (FIG. 1). The reader  10  responds to a successful read of the RFID tag  12 A,  12 B or machine-readable symbol  24 A,  24 B by illuminating the corresponding green LED  76 ,  78 , respectively, for a set period of time such as 5 seconds. The red LEDs  84 ,  86  can indicate unsuccessful or incomplete operations. The user receives visual feedback, where the color, position and sequence of the visual indicators  62  is consistent within, and across the RFID tag and symbol operating modes. Consistent feedback can reduce training time and costs, and can lead to more efficient operation of the reader  10 .  
     [0050] Similar to the visual indicators  62 , the speaker  66  provides consistent feedback within and across the operating modes. In the illustrated embodiment, the speaker  66  emits a “beep” or a “click” sound, although the speaker  66  can emit different and/or additional sounds. The speaker  66  can emit, for example, a single beep each time either an RFID tag  12 A,  12 B or a machine-readable symbol  24 A,  24 B is successfully read. When searching a field of RFID tags  12 A,  12 B for one or more particular tags, the speaker  66  can emit a click for each non-match and a beep for each match.  
     [0051] The user interface can also include an ON/OFF indicator  97 , and/or a Low Power indicator  99  to identify the operating condition of the reader  10 .  
     [0052]FIG. 4 shows an alternative set of visual indicators for the reader  10 . This alternative embodiment, and those alternative embodiments and other alternatives described herein, are substantially similar to previously described embodiments, and common acts and structures are identified by the same reference numbers. Only significant differences in operation and structure are described in detail below.  
     [0053] The reader  10  of FIG. 4 employs only three LEDs to simplify switching while providing the human-perceptible visual indications. A two state LED serves as the machine-readable symbol related indicator  87 . The machine-readable symbol indicator  87  produces no light in an OFF state and a Green light in an ON state. A three state LED serves as the RFID related indicator  89 . The RFID related indicator  89  produces a Green light in first ON state, a Yellow light in second ON state, and NO light in an OFF state. A two state LED serves as the ON/OFF indicator  97 . The ON/OFF indicator produces a Yellow light, or No light. The ON/OFF indicator is proximate the machine-readable symbol related and RFID related indicators  87 ,  89 . In FIG. 4, the mode switch  34  takes the form of a toggle or slider switch, having a neutral position (center), a symbol mode position (left of center) and an RFID mode position (right of center). The positions are consistent with the corresponding visual indicators  87 ,  89 , respectively.  
     [0054] FIGS.  5 A-C describe a variety of input and outputs signals for the reader  10 , and particularly for the audio indicator  64  and laser  53  of FIG. 2, and for the visual indicators  87 ,  89 ,  97  of FIG. 4. While the table is self-explanatory, a brief description of the columns follows. Column  31  defines a reader status or error conditions corresponding to reader activities. Column  33  describes the operation of the visual indicators  87 ,  89 ,  97  of FIG. 4, in response to the various reader status or errors conditions. Similarly, column  35  describes the operation of the audio indicator  64  in response to the various reader status or error conditions  33 . Column  37  describes the operation of the laser to produce the desired human-recognizable patterns corresponding to the various reader status or errors conditions  31 . Column  39  describes messages for display on the display  74  corresponding to the various reader status or errors conditions  31 . Column  41  describes PDT/Host messages corresponding to the various reader status or errors conditions  31 . Column  43  describes data and/or error codes sent to the host  33 , corresponding the various reader status or errors conditions  31 . As discussed above, these user indications provide a consistent interface for the user within and across the operating modes, permitting the user to efficiently operate the reader  10 .  
     [0055] The display  74  can additionally, or alternatively, provide the user other visual indications. For example, a graphical display  88  (FIG. 6), can employ a first set of icons  90  to indicate RFID tag activities and a second set of icons  92  to indicate symbol reading activities. (Note, typically only a single icon will be displayed at a time, although multiple icons are shown in FIG. 6 for the convenience of this description.) For example, screen icons  81 ,  83  and  85  can represent RFID reading, successful reading of the RFID tag  12 A,  12 B, and unsuccessful reading of RFID tag  12 A,  12 B, respectively. Similarly, screen icons  91 ,  93  and  95  can represent machine-readable symbol reading, successful reading of the machine-readable symbol  24 A,  24 B, and unsuccessful reading of the machine-readable symbol  24 A,  24 B, respectively.  
     [0056] Similarly, an alpha-numeric display  94  (FIG. 7) can employ a first set of words  96  to indicate RFID tag activities and a second set of words  98  to indicate symbol reading activities. (Again, typically only a single word will be displayed at a time, although multiple are shown in FIG. 7 for the convenience of this description.) The display  94  is self-explanatory and in the interest of brevity will not be further described. Other visual indications, as well as audio and tactile indications are of course possible.  
     Selected Methods of Operation  
     [0057] Different methods of operating the reader  10  or a reader having similar capabilities are disclosed below. As set out in the below methods, the intuitive and consistent operation of the user interface within and across operating modes can provide numerous benefits. While several methods are set out for illustration, other methods employing similar techniques are within the scope of the invention. Also, the following descriptions employ certain descriptions of user outputs (e.g., Beep, Click, Red LED, Yellow LED, and Green LED) for convenience of description. Those skilled in the art will appreciate that other sounds, colors, visual, tactile indications, and/or other human-perceptible indications could be used.  
     Single Tag Read Mode  
     [0058]FIG. 8 shows a method  100  of reading RFID tags  12 A- 12 B (FIG. 1) employing the reader  10  (FIGS.  1 - 3 ). Turning on the reader  10 , or switching into the RFID tag reading mode, can automatically cause the microprocessor  46  to start the method  100  in step  102 . Alternatively, or additionally, the user can cause the microprocessor  46  to start the RFID tag reading method  100  by selecting an appropriate key from the keypad  60  or icon from the display  74 . Upon starting in step  102 , the microprocessor  46  can perform an initialization process, for example loading appropriate operating instructions from the ROM  50  to the RAM  48 , initializing the characteristic data string buffer  49  and/or performing a series of systems checks on the various component and subsystems of the reader  10 , as set out in step  104 .  
     [0059] Under the instructions loaded in the RAM  48 , the microprocessor  46  activates the radio  44  in step  106 . In step  108 , the radio  44  receives data from the RFID tags  12 A,  12 B. The radio  44  can emit an interrogation signal to cause the RFID tags  12 A,  12 B to respond, or, the radio  44  can simply receive signals from RFID tags  12 A,  12 B that emit signals without interrogating the RFID tags. A variety of passive, active and hybrid RFID tags  12 A,  12 B are known in the art and will not be discussed in further detail. A discussion of RFID tags can be found in commonly assigned patent applications: U.S. Ser. No. 09/173,539, filed Oct. 15, 1998, entitled WIRELESS MEMORY DEVICE AND METHOD OF MANUFACTURE (Atty. Docket No. 480062.630); U.S. Ser. No. 09/164,203, filed Sep. 30, 1998, entitled MEMORY TAG AND METHOD OF MANUFACTURE (Atty. Docket No. 480062.632); U.S. Ser. No. 09/173,137, filed Oct. 15, 1998, entitled RF TAG HAVING STRAIN RELIEVED STIFF SUBSTRATE AND HYDROSTATIC PROTECTION FOR A CHIP MOUNTED THERETO (Atty. Docket No. 480062.635); and U.S. Ser. No. 09/164,200, filed Sep. 30, 1998, entitled CHIP PLACEMENT ON SMART LABELS (Atty. Docket No. 480062.642).  
     [0060] In step  110 , the microprocessor  46  determines whether duplicate tag data should be suppressed. If suppressed, previously read or acquired data will not be stored or reported a second time. Suppression can be a user selection, or can be a selection transferred from the host  23 , or can be preset, for example by the reader manufacturer or owner. If suppression is not active, the reader  10 , in step  112 , automatically transmits the read data, for example to the host  23 , and provides an indication to the user that the data has been received and transmitted. To provide the indication, the reader  10  activates the speaker  66  to emit a single “beep” and activates the Green RFID related LED  76  for a short time, in steps  114 ,  116 , respectively. Control passes to an end of the routine  100 , in step  118 .  
     [0061] If suppression is active, the microprocessor  46 , compares a characteristic data string from the received data to other characteristic data strings stored in the characteristic data string buffer  49 , in step  120 . The characteristic data string can be any string of characters stored in the RFID tags  12 A,  12 B that permit the reader  10  to determine whether a particular RFID tag  12 A,  12 B has been read more than once. For example, the characteristic data string can be a unique identifier programmed into each of the RFID tags  12 A,  12 B. Alternatively, the characteristic data string can be the entire set of data stored in the RFID tag  12 A,  12 B, or can be any subset or field of data recognizable by position, offset, delimiter or other such field identifier. The microprocessor  46  branches at step  122  based on the determination of whether the received characteristic data string corresponds, or matches, any of the stored data strings.  
     [0062] If the received characteristic data string corresponds to, or matches, any of the stored characteristic data strings, the reader  10  provides an indication that the RFID tag  12 A,  12 B has been read again, activating the speaker  66  to emit a single “click” and activating or “flashing” the Red RFID related LED  84  in steps  124 ,  126 , respectively. The microprocessor  46  determines in step  128 , if the reader  10  is finished reading RFID tags  12 A,  12 B, as described in detail below.  
     [0063] If the received characteristic data string does not correspond to, or match any of the stored data strings, the microprocessor  46  updates the characteristic data string buffer  49  containing the read characteristic data strings, for example storing the newly received characteristic data string to the buffer  49  in step  130 . The reader  10  can automatically transmit the read data in step  132 , for example to the host  23  (FIG. 1). The reader  10  also provides an indication that a new RFID tag  12 A,  12 B has been read (e.g., read for the first time since the buffer  49  was initialized), activating the speaker  66  to emit a “beep” in step  134  and activating the Green RFID related LED  76  in step  136 . Control passes to the end of the routine  100  in step  118 .  
     [0064]FIG. 9 is a flowchart of a method  200  of determining when a reader  10  is finished reading. The microprocessor  46  can execute this method  200  in place of each step labeled “DONE” in the various other methods, such as at step  128  of FIG. 8 (discussed above), or in the other Figures (discussed below). As set out in the Figures, the method  200 , starting at step  202 , acts as a function or subroutine, returning a Boolean value (e.g., TRUE/FALSE, YES/NO, or DONE/NOT DONE conditions). While the method  200  could be implemented as an integral part of the other methods discussed herein, it is set out separately for ease of discussion.  
     [0065] At step  240 , the microprocessor  46  determines whether the trigger  20  has been released. A trigger release indicates that the user is finished reading. If the trigger  20  has been released, the microprocessor  46  sets the Boolean value to “DONE” at step  242 , and passes control to an end of the routine  200  at step  218 , returning the appropriate Boolean value. For example, when returning to the method  100  (FIG. 8), the condition “DONE” can cause the reader  10  to stop interrogating RFID tags  12 A,  12 B.  
     [0066] If the trigger  20  has not been released, the microprocessor  46  in step  244  determines whether a timeout condition has been exceeded. For example, the reader  10  can assume that all RFID tags  12 A,  12 B have been read if a new (e.g., not previously read) tag is not found after some length of time or some number of consecutive repeatedly read RFID tags  12 A,  12 B. While the length of time or number of repeated reads can be preset, the length or number of repeats can also be determined during the reading, for example as a function of RFID tag density (e.g., number of RFID tags per unit time). The microprocessor  46  can rely on an internal clock or a separate clock circuit (not shown) in measuring the timeout period. Employing RFID tag density to calculate the stopping condition “on the fly” reduces the likelihood of ending a search prematurely .  
     [0067] If the timeout condition is exceeded, the reader  10  considers reading to be finished, sets the Boolean value to “DONE” at step  242 , and passes control to the end of the method  200  at step  218 , producing the appropriate Boolean value for determining the next operation, such as turning the radio OFF. If the timeout condition is not exceeded, the microprocessor  46  determines whether a stop command has been received from the host  23  in step  246 . If a stop command has been received, the Boolean value is again set to “DONE” at step  242 , and control passes to the end of the method  200  at step  218 . If a stop command has not been received from the host  23 , the microprocessor  46  at step  248 , determines whether all RFID tags  12 A,  12 B have been read. If all RFID tags  12 A,  12 B have been read, the Boolean value is set to “DONE” at step  242  and control passes to the end of the method  200  at step  218 , returning the appropriate response. If all RFID tags  12 A,  12 B have not been read, the Boolean value is set to “NOT DONE” at step  250  and control passes to the end  218 , thereby returning the appropriate Boolean value.  
     Multi Tag Read/Write Modes  
     [0068]FIG. 10, shows an additional, or alternative embodiment of operating under the present invention. Similar steps in the methods are assigned reference numerals that have the two least significant digits in common (e.g., the “Start” step is respectively numbered:  102 ,  202 ,  302 , . . . ,  702  in FIGS.  6 - 12 , respectively).  
     [0069]FIG. 10 shows a method  300  of reading multiple RFID tags  12 A,  12 B (FIG. 1) employing the reader  10  (FIGS.  1 - 3 ). In a similar fashion to the method  100 , the microprocessor  46  starts executing the method  300  at step  302 , initializing the reader  10  at step  304 , turning ON the radio  44  in step  306 , and receiving responses from the RFID tags  12 A,  12 B in step  308 . In step  320 , the microprocessor  46  compares a characteristic data string from the received data to other characteristic data strings stored in the characteristic data string buffer  49  to determine whether the reader  10  has read the particular RFID tag  12 A,  12 B before. The microprocessor  46  branches at step  322  based on the determination of whether the received characteristic data string corresponds, or matches, any of the stored data strings.  
     [0070] If the received characteristic data string corresponds to, or matches, any of the stored characteristic data strings, the microprocessor  46  adds the read characteristic data string to the characteristic data string buffer  49 , at step  330 . The reader  10  provides an indication that the read RFID tag  12 A,  12 B has been previously read, activating the speaker  66  to emit a single “click” and activating or “flashing” the Red RFID related LED  84  at steps  352  and  354 , respectively. In step  356 , the microprocessor  46  examines a counter (“Retry”) to determine whether a maximum number of iterations has been exceeded without finding a “new” (e.g., not previously read) RFID tag  12 A,  12 B. If the number of iterations without encountering a new RFID tag  12 A,  12 B has been exceeded, control passes to an end of the method  300  at step  318 . If the number of iterations without encounter a new RFID tag  12 A,  12 B has not been exceeded, the microprocessor  46  increments the Retry counter in step  358 , and determines in step  328  whether the reader  10  is finished reading RFID tags  12 A,  12 B, as described in detail above with respect to method  200  (FIG. 9). The microprocessor  46  returns to receiving RFID tag responses in step  308 , or passes control to the end of the method  300  at step  318  based on the Boolean value returned by the method  200  (FIG. 9).  
     [0071] If the received characteristic data string does not correspond to, or match any of the stored data strings, the microprocessor  46  resets the Retry counter in step  360 , and adds the read characteristic data string to the characteristic data string buffer  49  in step  362 . The reader  10  in step  364 , automatically transmits the read data, for example to the host  23 . The reader  10  also provides an indication that a new RFID tag  12 A,  12 B has been read (e.g., read for the first time since the buffer  49  was initialized), activating the speaker  66  to emit a “beep” in step  314  and activating the Green RFID related LED  76  in step  316 . The microprocessor  46  determines in step  328  whether the reader  10  is finished reading RFID tags  12 A,  12 B, as described in detail above with respect to method  200  (FIG. 9). The microprocessor  46  returns to receiving RFID tag responses in step  308  or passes control to the end of the method  300  in step  318  based on the condition returned by the method  200 .  
     Inclusive Search  
     [0072] The reader  10  can perform an “inclusive” search, such as finding all RFID tags  12 A,  12 B on a list of RFID tags  12 A,  12 B. FIG. 11 shows a method  400  for performing an inclusive search. The user can start the inclusive search  400  by, for example, selecting an appropriate key or icon as in step  402 . The microprocessor  46  performs an initialization at step  404 , for example loading a list of characteristic data strings for the RFID tags  12 A,  12 B to be located or identified into the characteristic data string buffer  49 . The list of characteristic data strings can, for example, be downloaded from the host  23  via interface  22 . The microprocessor  46  turns ON the radio  44  at step  406 .  
     [0073] In step  408 , the radio  44  interrogates the RFID tags  12 A,  12 B to receive response signals containing the respective characteristic data strings. Alternatively, the radio  44  can receive the response signals without interrogating if the RFID tags  12 A,  12 B are active and periodically transmit data without requiring initiation by an interrogation signal. In step  420 , the microprocessor  46  compares the received characteristic data string with the characteristic data strings stored in the characteristic data string buffer  49 . The microprocessor  46  branches at step  422 , based on the determination of whether the received characteristic data string corresponds, or matches, any of the stored data strings.  
     [0074] If the read characteristic data string corresponds to, or matches any of the stored characteristic data strings, then one of the RFID tags  12 A,  12 B has been found and the reader  10  reports such to the user and/or host  23 . The reader  10  provides the user indication by activating the speaker  66  to “beep” in step  414  and activating or “flashing” the Green RFID related LED  76  in step  416 . If the read characteristic data string does not correspond to, or match any of the stored characteristic data strings, then one of the RFID tags  12 A,  12 B has not been found, and the reader  10  reports such to the user, and/or host  23 . The reader  10  provides the user indication by activating the speaker  66  to “click” in step  424  and activating or “flashing” the Red RFID related LED  84  in step  426 .  
     [0075] After providing the user indications, the microprocessor determines whether the reader is finished reading, in step  428 . If the reading is finished, the returned Boolean value (i.e., DONE) causes control to pass to an end of the inclusive search routine  400  in step  418 . If the reading is not finished, the returned Boolean value (i.e., NOT DONE) causes the radio  22  to continue receiving response signals, passing control to step  418 .  
     Exclusive Search  
     [0076] The reader  10  can perform an “exclusive” search, such as finding any RFID tags  12 A,  12 B not on a list of RFID tags  12 A,  12 B. FIG. 12 shows a method  500  for performing an exclusive search. The user can start the exclusive search  500  at step  502  by, for example, selecting an appropriate key or icon. The microprocessor  46  performs an initialization at step  504 , for example loading a list of characteristic data strings for the RFID tags  12 A,  12 B to be located. At step  506 , the microprocessor turns ON the radio  44 .  
     [0077] In step  508 , the radio interrogates the RFID tags  12 A,  12 B to receive response signals containing the respective characteristic data strings. Alternatively, the radio can receive the response signals without interrogating if the RFID tags  12 A,  12 B are active and periodically transmit without requiring an interrogation signal. In step  520 , the microprocessor  46  compares the received characteristic data string with the characteristic data strings stored in the characteristic data string buffer  49 . The microprocessor  46  branches at step  566 , based on the determination of whether the received characteristic data string does not correspond, or match, any of the stored data strings.  
     [0078] If the read characteristic data string does not correspond to, or match any of the stored characteristic data strings, then one of the RFID tags  12 A,  12 B missing from the list has been found, and the reader  10  reports such to the user and/or host  23 . The reader  10  provides the user indication by activating the speaker  66  to “beep” in step  514 , and activating or “flashing” the Green RFID related LED  76  in step  516 . If the read characteristic data string corresponds to, or matches any of the stored characteristic data strings, then one of the RFID tags  12 A,  12 B missing from the list has not been found, and the reader  10  reports such to the user, and/or host  23 . The reader  10  provides the user indication by activating the speaker  66  to “click” in step  524 , and activating or “flashing” the Red RFID related LED  84  in step  526 .  
     [0079] After providing the user indications, the microprocessor  46  determines whether the reader  10  is finished reading, in step  528 . If the reading is finished, the returned Boolean value (i.e., DONE) causes control to pass to an end of the exclusive search routine  500  in step  518 . If the reading is not finished, the returned Boolean value (i.e., NOT DONE) causes the radio to continue receiving response signals, passing control to step  508 .  
     Association of RFID Tag Data With Item Using Machine-Readable Symbol  
     [0080] Often a user desires to make a physical association between the data read from one of the RFID tags  12 A,  12 B and a particular object or item  14  (FIG. 1). While the RFID tag  12 A,  12 B may be attached to, or contained with the item, it can be difficult to identify the particular RFID tag  12 A,  12 B that is being read. For example, trying to identify one or more bags in a cargo hold, or cargo container on an airliner is difficult and time consuming using only RFID tags  12 A,  12 B. Each bag would have to be isolated and the RFID tag  12 A,  12 B read to ensure that the read data came from the RFID tag  12 A,  12 B associated with the particular bag. At least one proposed solution involves placing human-perceptible indicators on each of the RFID tags, as disclosed in the commonly assigned U.S. Ser. No. 09/, filed, 1999, and entitled “METHOD AND APPARATUS FOR HUMAN-PERCEPTIBLE IDENTIFICATION OF MEMORY DEVICES, SUCH AS RFID TAGS” (Atty. Docket No. 480062.663). This solution can be relatively expensive since each RFID tag  12 A,  12 B requires its own human-perceptible indicator which complicates RFID tag manufacture.  
     [0081]FIG. 13 shows a method  600  of associating the read data from the RFID tag  12 A,  12 B with a particular one of the items  14 . The association method  600  assumes that an RFID tag  12 A,  12 B has already been read, a characteristic data string retrieved and stored, for example, in the characteristic data string buffer  49 . The user can start the association method  600  in step  602 , as discussed generally above. Alternatively, the reader  10  can be configured to automatically start the association method  600  at step  602 . In step  668 , the microprocessor  46  enters the symbol reading mode. The user activates the trigger  20  in step  670 , causing the microprocessor  46  to activate the image sensor  52  to read the machine-readable symbol  24 A,  24 B at which the reader  10  is directed. In step  672 , the image sensor  52  acquires data from the machine-readable symbol  24 A,  24 B by scanning, digitizing, or by any commonly known methods in the relevant art. As part of acquiring the data, the microprocessor  46 , or a dedicated processor (not shown), decodes the image to acquire a characteristic data string encoded in the machine-readable symbol  24 A,  24 B. Methods and apparatus for acquiring data from machine-readable symbols are commonly known in the art, and are specifically taught in  The Bar Code Handbook  3 rd    Ed , by Palmer, Roger C, Helmers Publishing, Inc. (ISBN 0-911261-09-5), and, in the interest of brevity, will not be described in further detail.  
     [0082] To determine whether the machine-readable symbol  24 A,  24 B that the reader  10  is pointing at is associated with the RFID tag data read by the reader  10 , the microprocessor  46  compares a characteristic data string read from the RFID tag  12 A,  12 B with the characteristic data string read from the machine-readable symbol  24 A,  24 B, in step  620 . The user can visually associate the RFID tag  12 A,  12 B with the machine-readable symbol  24 A,  24 B since the RFID tag  12 A includes the machine-readable symbol  24 A, or the RFID tag  12 B and machine-readable symbol  24 B are carried by the same item  14 , or can be visually associated is some other manner. The user can therefore determine that the data is from a particular RFID tag  12 A,  12 B when a match is indicated by the reader  10 .  
     [0083] If the characteristic data string from the machine-readable symbol  24 A,  24 B corresponds to, or matches, the characteristic data string from the RFID tag  12 A, 12 B, the reader  10  provides an indication that an association exists. To provide the indication, the microprocessor  46  Activates the speaker  66  to emit a single “beep” in step  614  and activates or “flashes” the Green RFID related LED  76  and the Green symbol related LED  78  in step  674 . The RFID related and the symbol related LEDs  76 ,  78  are each activated, indicating that both an RFID tag  12 A,  12 B and a machine-readable symbol  24 A,  24 B have been located, providing a consistency across the user interface.  
     [0084] In step  676 , the microprocessor  46  can turn OFF the image sensor  52  after having found an association. In step  612 , the reader  10  can report the data, for example transmitting the RFID data to the host  23  via the communications port  38  and interface  22 . In step  676 , the reader  10  can receive a direction or command from the host  23  via the interface  22  and the communications port  38 . In step  678 , the microprocessor  46  determines whether the buffer should be modified based on the command from the host  23 . If the buffer is to be modified, the microprocessor  46  modifies the buffer at step  680 , and passes control to an end of the association method  600  in step  618 . Otherwise, the microprocessor  46  passes control directly to the end of the association method, in step  600 , without modifying the buffer.  
     [0085] If the characteristic data string from the machine-readable symbol  24 A,  24 B does not correspond to, or match the characteristic data string from the RFID tag  12 A, 12 B, the reader  10  provides an indication that an association does not exist. To provide the indication, the microprocessor  46  activates the speaker  66  to emit a three “Beeps” in step  682 , and activates or “flashes” the Red RFID related LED  84  and the Green symbol related LED  78  in steps  626 ,  684 , respectively. The Green symbol related LED  78  is flashed to indicate that a symbol has been successfully read, while the Red RFID related  84  is flashed to indicate that the data is not associated with the machine-readable symbol  24 A,  24 B, further providing consistency across the user interface. The microprocessor  46  proceeds to the end of the method  600 , in step  618 .  
     Automatically Reading A Symbol Based On Proximity To RFID Tag, or Frequency of RFID Tag&#39;s Responses  
     [0086]FIG. 14 shows a method  700 , in which the reader  10  automatically reads the machine-readable symbol when the reader  10  is within a defined proximity of the RFID tag  12 A, and hence within the defined proximity of the machine-readable symbol  24 A. The automated symbol reading feature provides numerous benefits, for example the automated symbol reading feature can simplify operation of the reader, and/or reduce the probability of user error. The automated symbol reading feature can also reduce the amount of labor required to operate the reader  10 , and can even eliminate the need for a human operator. The method  700  of FIG. 14 can be used as part of, or with, many of the previously described methods.  
     [0087] The antenna  42  in the reader  10  can be directionally sensitive. The directionally sensitive antenna  42  has a directional range, in other words, the antenna is more sensitive in certain directions than other directions. As the reader  10  approaches a particular RFID tag  12 A,  12 B, that RFID tag  12 A,  12 B spends a higher percentage of time within the range of the reader  10 . In contrast, other RFID tags  12 A,  12 B are in the range a lower percentage of time. Thus, as the reader  10  comes within a predefined proximity of the RFID tag  12 A,  12 B, the number of “hits” (i.e., reading an RFID tag having a desired characteristic data string) will increase, and the number of “misses” (i.e., reading RFID tags not having the desired characteristic data string) will decrease. The user may recognize this from an increase in the number of “Beeps” and a decrease in the number of “Clicks” emitted by the reader  10 . The microprocessor  46  in the reader  10 , can keep track of the number of hits and the number of misses for some unit length of time, steps  786 ,  788 , respectively. The microprocessor  46  can determine a ratio of the number of hits per unit of time and the number of misses per unit of time. Alternatively, the host  23  can process the same information.  
     [0088] In step  790 , the microprocessor  46  determines whether the ratio of hits to misses exceeds a symbol reading threshold. If the ratio does not exceed the symbol reading threshold, the microprocessor  46  returns to step  786  and the reader  10  continues to read the RFID tags  12 A,  12 B, continually revising and checking the ratio against the threshold.  
     [0089] If the ratio exceeds the symbol reading threshold, the microprocessor  46  turns the image sensor  52  ON, for example, switching from the RFID reading mode to the symbol reading mode in step  768 . The microprocessor  46  controls the image sensor  52  to image and decode the machine-readable symbol  24 A,  24 B in  772 . In step  774 , the microprocessor  46  turns the image sensor  52  OFF, thereby conserving power. In step  720 , the microprocessor  46  compares the characteristic data string-from the machine-readable symbol  24 A,  24 B to the characteristic data string from the RFID tag  12 A,  12 B.  
     [0090] If the characteristic data string from the machine-readable symbol  24 A,  24 B corresponds to, or matches, the characteristic data string from the RFID tag  12 A,  12 B, the reader  10  provides an indication that an association exists. To provide the indication, the microprocessor  46  activates the speaker  66  to emit a single “Beep” in step  714  and activates or “flashes” the Green RFID related LED  76  and the Green symbol related LED  78  in step  774 . The RFID related and the symbol related LEDs  76 ,  78  are each activated, indicating that both an RFID tag  12 A,  12 B and a machine-readable symbol  24 A,  24 B have been located, providing a consistency across the user interface.  
     [0091] In  712 , the reader  10  can report the data, for example automatically transmitting the RFID data to the host  23  via the communications port  38  and interface  22 . In step  776 , the reader  10  can receive a direction or command from the host  23  via the interface  22  and the communications port  38 . In step  778 , the microprocessor  46  determines whether the characteristic data string buffer  49  should be modified based on the command from the host  23 . If the buffer  49  is to be modified, the microprocessor  46  modifies the buffer at step  780 , and passes control to an end of the association method  700  at step  718 . Otherwise, the microprocessor  46  passes control directly to the end of the association method  700  at step  718  without modifying the characteristic data string buffer  49 .  
     [0092] If the characteristic data string from the machine-readable symbol  24 A,  24 B does not correspond to, or match the characteristic data string from the RFID tag  12 A, 12 B, the reader  10  provides an indication that the association does not exist. The microprocessor  46  activates the speaker  66  to emit three “Beeps” in step  782 , and activates or “flashes” the Green symbol related LED  78  and the Red RFID related LED  84  in steps  784  and  726 , respectively. The Green symbol related LED  78  is flashed to indicate that a symbol has been successfully read, while the Red RFID related  84  is flashed to indicate that the data is not associated with the machine-readable symbol  24 A,  24 B, further providing consistency across the user interface.  
     Summary  
     [0093] The various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents, patent applications and publications referred to in this specification are incorporated by reference. Aspects of the invention can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments of the invention.  
     [0094] Although specific embodiments of and examples data carrier readers and reading are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the invention, as will be recognized by those skilled in the relevant art. The teachings provided herein of the invention can be applied to any data carrier reader, not necessarily the exemplary combination RFID tag and symbol reader generally described above.  
     [0095] For example, some of the structures and methods can be used with readers capable of reading only RFID tags. Some of the structures and methods can be used with readers capable of reading only machine-readable symbols. Some of the structures and methods can be suitable with readers for other data carriers, such as optical tags and touch memory devices. The methods and structures are generally applicable with other wireless memory devices, not just radio frequency, and the term RFID as used herein is meant encompass wireless memory devices operating in all ranges of the electromagnetic spectrum, not only the radio frequency portion. Similarly, the structures and methods disclosed can work with any variety of modulation techniques, including, but not limited to, amplitude modulation, frequency modulation, phase modulation and/or pulse width modulation. The structures and methods can also be applied to various machine-readable symbologies, including, but not limited to, bar codes, stacked codes, area and/or matrix codes. The image sensor  52  can be any type of image capture device, including laser scanners, one- and two-dimensional charged coupled devices, Vidicons, and the like.  
     [0096] These and other changes can be made to the invention in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all apparatus and methods that operate in accordance with the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to be determined entirely by the following claims.