Abstract:
An item price notification system automatically interrogates product labels to determine product, pricing, and other unique data. The system uses a radio frequency (RF) radio frequency transceiver to generate an RF field to communicate with radio frequency identification (radio frequency transponders) transponders mountable to product display shelves. The radio frequency transponders contain information such as pricing information, nutritional information, and other unique data about the various products. As the RF radio frequency transceiver moves into proximity to various radio frequency transponders for a variety of products, the unique data are received by the RF radio frequency transceiver and are displayed for the user. The displayed data allows a user to make comparisons between products, and the system display and memory allow a user to store the unique data for those products and to make instant and cumulative product, price, and other comparisons.

Description:
FIELD OF THE INVENTION 
   This invention generally relates to retail pricing systems, and methods for managing pricing, consumer comparisons, and inventory of goods. 
   BACKGROUND OF THE INVENTION 
   The traditional method for informing consumers of item prices in a retail setting is to place price labels on the shelves under the items. These labels are normally made of paper or of another single-use material and must be manually updated when prices change or when an item goes on sale. There are many advantages to making this item information available electronically including greater accuracy, lower labor costs, greater flexibility, and more timely and responsive pricing practices. To achieve these advantages, electronic shelf labels may be placed on the shelves. Retailer merchandisers place electronic shelf labels on stock shelves to display item information such as the regular product price, any promotional pricing, and the unit price of the item, as well as any other advertising or consumer information. Electronic shelf labels may also be remotely updated from a central pricing database. Electronic shelf labels enable merchants to update price changes on the shelves and checkout stands of multiple stores at the same time. 
   These electronic shelf labels are programmed using radio frequency or infrared (IR) interfaces, or by wiring the shelves to accept periodic inputs from another device. But there are disadvantages to pricing methods using electronic shelf labels. Power and communication means must be provided to the individual labels. If batteries are used to provide power to each label, they must be changed on a regular basis. With 30,000 items in a supermarket, this could be prohibitive. Wired shelves do not require the routine change of batteries, but they limit a store&#39;s ability to reallocate shelf space and reconfigure the shopping aisles by moving display shelves since each shelf is now specifically wired for a particular product. 
   Additionally, electronic shelf labels do not provide the consumer with item information in a side-by-side comparison of similar products. The consumer must manually locate and inspect each individual electronic shelf label and use these individual labels to mentally track and compare quantities, pricing, and other unique item data. Similar products may be located further down the aisle or on a shelf higher or lower than the consumer is able to properly perceive or comfortably investigate. Comparisons are often made only between two adjacent items, and the consumer is not able to adequately evaluate his retail alternatives. In fact, suppliers pay thousands of dollars in slotting allowances to distributors for product placement on store shelves. Premiums are paid for eye-level shelves or special displays, and an entire science of shelf space allocation has evolved so suppliers may increase the likelihood that consumers will consider their products and ultimately select those products for purchase. However, neither electronic shelf labels nor paper labels adequately provide consumers with readily comparable item data from which to base their purchase decisions. 
   What is needed is a new type of item information system that provides consumers with unique item data and enables consumers to make immediate comparisons between similar items resulting in an informed purchase decision. 
   In another approach, price-checking stations have been provided in retail environments that are adapted to read a barcode and provide price information. More recently, radio frequency transponders have been proposed to replace barcodes in a wide variety of applications. Such radio frequency transponders are typically capable of receiving a radio frequency interrogation signal and automatically generating a responsive radio frequency signal. In many applications, the responsive signal contains some form of data that identifies the transponder or that identifies items associated with the transponder. Radio frequency transponders are often embedded in products or product containers and are used to track items for inventory control, for performing security operations and anti-theft measures, for collecting tolls and other payments, and for many other purposes. 
   Radio frequency transponders can be active devices that have internal power source and have their own radio frequency transmitters that can generate signals using the internal power source, or passive devices, that do not have an internal power source and that can provide responsive signals only when sufficient power is supplied by an interrogation signal. Radio frequency transponders may have a range from several millimeters to many meters depending upon the available transmission power and antenna size. Radio frequency transponders employing on-board power supplies have a life limited by the life of the power supply. Passive radio frequency transponders have a longer useful life and are typically less expensive than radio frequency transponders with on-board power supplies. However, since radio frequency transponders without their own power source use some of the energy of the radio frequency transceiver as their source of their power, these radio frequency transponders typically require a more powerful radio frequency interrogating signal than a system that employs active radio frequency transponders. 
   A radio frequency transceiver transmits an interrogation signal, for example, in the form of continuous electromagnetic wave or a series of waves to sense an object containing a radio frequency transponder. When the radio frequency transceiver and a radio frequency transponder are brought into proximity so that the radio frequency field generated by the radio frequency transceiver reaches the radio frequency transponder, the receiving radio frequency transponder transmits a modulated signal in response to the radio frequency transceiver&#39;s interrogation signal. The radio frequency transceiver receives this information and decodes it. Depending upon the configuration of the radio frequency transceiver, this decoded information may then be stored or re-transmitted to a host computer for further processing and action. 
   While the potential convenience of placing such radio frequency transponders on individual products to replace barcodes, for example in retail environments, is well appreciated, the cost of providing such transponders for each product is currently prohibitive. 
   SUMMARY OF THE INVENTION 
   The present invention is a system and method of alerting consumers to the presence of nearby items and providing item information that can be reviewed while the consumers are shopping. In certain aspects of the invention, this allows, for example, a direct comparison of similar goods and products. The present invention provides an item information device that utilizes a radio frequency transceiver to automatically transmit interrogation signals to radio frequency transponders that are located proximate to retail shelves having items thereon and to allow the consumers to access unique item data that is stored in the radio frequency transponders. When interrogated, radio frequency transponders associated with the items on the retail shelves respond with the Universal Product Code (UPC) and other unique data of the products with which the radio frequency transponders are associated. As the radio frequency transceiver is moved into proximity to various radio frequency transponders, the unique data are displayed for the user. The system and method of the present invention allows a user to make comparisons between products based upon a variety of criteria associated with the products. Some embodiments of the system and method of the present invention, further allow a user to store the unique data for those products and to make preliminary and ultimate product and price comparisons and purchase decisions. 
   The present invention uses radio frequency transponders that, once placed on the shelves, no longer require a power source and can easily be moved with the product or display area as needed and can easily be up. In certain embodiments, a portable item information device is provided and can, for example, be joined to a shopping cart or like customer item carrier. The portable item information device contains a radio frequency transceiver, which sends interrogation signals that solicits responses from proximate transponders from which the item information device can identify items in its vicinity as the shopping cart is moved about. The portable item information device has a display that that can be used to provide an image having graphics and text or other content, and a controller that is adapted to determine output data for presentation on the display, and to cause the display to show such item information such as item names, prices, unit prices and other unique data such as pictorial or graphic representations associated with the items. Sale items may be indicated by a flashing display or some other attention-getting graphic. In some embodiments, the display program may show a running total price of the items selected or a running total of calories or other unique data inherent to the individual product. The consumer may select any number of criteria to compare similar products. In this fashion, the system and method of the present invention gives the consumer immediate feedback regarding which items are nearby, which items are available as potential purchases, allows consumers to compare similar items prior to purchase selection, and gives consumers information to avoid potential discrepancies and expedite checkout. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent, and the invention itself will be better understood by reference to the following description of the invention taken in conjunction with the accompanying figures where: 
       FIG. 1  is an overview block diagram of the invention in use in a typical retail environment; 
       FIG. 2  is a block diagram of the interaction between radio frequency transponders, a radio frequency transceiver, and computer system of the present invention; 
       FIG. 3  shows an exterior view of one embodiment of a portable item information system presenting an image; 
       FIGS. 4A ,  4 B, and  4 C show examples of the present invention in use in a retail environment; and 
       FIGS. 5A ,  5 B, and  5 C show examples of display screens of the present invention in use in a retail environment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention is described in detail with particular reference to certain preferred embodiments, but within the spirit and scope of the invention, it is not limited to such embodiments. It will be apparent to those of skill in the art that various features, variations, and modifications of the invention can be included or excluded, within the limits defined by the claims and the requirements of a particular use. 
   The present invention extends the capabilities of shoppers in a retail environment to locate goods and to compare characteristics of similar goods and products. The various embodiments of the present invention have particular advantages over prior systems such as those providing basic pricing information of goods selected and placed in a shopping cart, because a direct comparison of similar goods is now possible without removing the various products under consideration from their display shelves or display areas. In addition to a comparison of similar products, the present invention is a system and method for item price notification that provides a shopper with numerous customizable comparison points. 
     FIG. 1  is a block diagram showing a sales environment  100  adapted with one embodiment of the item information system of the invention. Sales environment  100  is shown having multiple display shelves  190 , each outfitted with shelf tags  101 . Display shelves  190  may also be cabinets, racks, kiosks, or any other type of storage unit that permits customer and employee access to inventory items. Each shelf tag  101  contains a radio frequency transponder  105 . In this embodiment, each type of unique item  107  stored on display shelves  190  is associated with a passive radio frequency transponder  105 , which has item information stored therein and which generates a responsive signal indicative of the item information when a radio frequency transceiver that is within a proximate distance generates an appropriate interrogation signal. That is, each unique item  107  does not have a radio frequency transponder  105 , but rather there is a single radio frequency transponder  105  for the shelf space  106  dedicated to stocking unique item  107 . It will be appreciated that, in other embodiments, one transponder  105  can be associated with more than one unique item that is located proximate to transponder  105 . 
   For example, cans of one vendor&#39;s (Vendor E) tomato soup can be stored in shelf space  106 , on display shelf  190  with radio frequency transponder  105   e.  When interrogated, radio frequency transponder  105   e  having data therein that is indicative of the item information, transmits a responsive signal that is indicative of the item information such as information used to denote the vendor, the price of the can of soup, the volume or weight of the soup, the per unit price of the soup, the recommended serving size, the number of calories in each serving, and other item information for which consumers may be interested. Similarly, radio frequency transponder  105   d  will be adapted to transmit similar information regarding unique items  107   d  stored in shelf space  106   d . While the above list of item information may contain many of the most desired data regarding the product, it is by no means inclusive, and other item information may be transmitted by radio frequency transponders  105  to provide consumers with additional information. One of ordinary skill in the art would be expected to customize the transmitted information based upon consumer&#39;s preferences, vendor&#39;s needs, and/or proprietor&#39;s differences. This information would then be stored as information fields in radio frequency transponder  105 . 
   The block diagram of  FIG. 1  further shows shopping cart  170  equipped with a portable item information device  150  having, in this embodiment, a display screen  175 , memory  135 , a control circuit  140  and radio frequency transceiver circuit  120  adapted to generate an interrogation signal that has sufficient power so that the polling signal can be received by any of the plurality of radio frequency transponders within a proximate distance and further supplying sufficient power to the transponders so that the transponders can use the supplied power to generate responsive signals having data indicative of the item information stored therein; the radio frequency transceiver circuit further being adapted to sense the responsive signals and to provide item data to a control circuit based upon the data in the responsive signals. Control circuit  140  is operably connected to radio frequency transceiver circuit  120 , memory  135  and display screen  175 . Control circuit  140  can comprise a micro-processor, micro-controller, application specific integrated circuit and/or other conventional control circuit structures. Control circuit  140  is adapted to receive the item data from transceiver circuit  120  to determine output information based upon the received item data and to cause display screen  175  to present an image based upon the output information. 
     FIG. 2  illustrates interaction between portable item information device  150  as a customer moves shopping cart  170  down aisle  185  in sales environment  100 . 
   As shown in  FIG. 2 , radio frequency transponder  105  stores information related to items in the form of an entry  252 , and other information fields  255  that correspond to entry  252 . While only a single entry  252  and field  255  is shown for each radio frequency transponder  105 , many more entries and fields may be stored in each radio frequency transponder. These entries  252  and information fields  255  are used to convey necessary item information regarding each unique item  107 . While many more shelf tags  101  and corresponding radio frequency transponders  105  may be used on any display shelf  190 , for illustrative purposes as shown in  FIG. 2 , and for brevity, three shelf tags  101   a ,  101   b ,  101   c , and three corresponding radio frequency transponders  105   a ,  105   b , and  105   c  are shown. 
   As further shown in  FIG. 2 , radio frequency transceiver circuit  120  transmits an interrogation signal  210  which is also tuned to the detection frequency of radio frequency transponder  105 . As shopping cart  170  is pushed down aisle  185 , it is brought into proximity with radio frequency transponders  105   a ,  105   b ,  105   c  which are thereby subjected to interrogating signals  210   a ,  210   b ,  210   c . In response to the interrogation signals, radio frequency transponders  105   a ,  105   b ,  106   c  generate responsive signals  215   a ,  215   b  and  215   c  respectively. Responsive signals  215   a - 215   c  are detected by radio frequency transceiver circuit  120  thereby indicating the presence of shelf tags  101  within the proximate distance of radio frequency transceiver circuit  120 . Typically, the proximate distance is controlled by three factors, the strength of the interrogation signals  210 , the efficiency with which transponders  105  convert energy from an interrogation signal into a responsive signal, and the receptive sensitivity of radio frequency transceiver circuit  120 . 
   Responsive signals  215  received by radio frequency transceiver circuit  120  are converted into item data that is provided to control circuit  140  which determines output information based upon the received item data. The output information can contain item data or be derived from item data, and the prepared image can be formed to show the data received, a summary of the item data received, and/or to show output information obtained from a database  245  having one or more records  250  that have such output information stored therein in association with the item data so that output information, such as an advertisement for a product can be obtained from database  245  using received item data. The item data received from radio frequency transceiver circuit  120  can also be channeled to external devices, such as a remote server  144 , which can have database  245  from which a control circuit  140  can receive other output information and can prepare an image based upon the available output information. Display screen  175  then shows the prepared image, including item data, in a readable format that a consumer may readily manipulate via input keys (not shown) on display screen  175 . Display screen  175  can be any suitable display screen including a touch screen device or a display screen manufactured by using coated cholesteric LCD technology. Coated cholesteric displays have the advantages of size, flexibility, ease of replacement, and durability since they are glass-free which is a safety consideration in a consumer environment. Since radio frequency transceiver circuit  120  continually transmits interrogation signals  210  to radio frequency transponders  105 , and thereby continually receives responsive signals  215  from radio frequency transponders  105 , a steady stream of item information is received and images can be prepared based upon this and displayed as a consumer moves shopping cart  170  down aisle  185 . 
   Based upon the sensitivity and transmission power of radio frequency transceiver circuit  120  and the ability to multiplex transmission and reception of interrogation signals  210  and responsive signals  215 , a plurality of radio frequency transponders  105  may be read substantially simultaneously. Because the transmission interaction between radio frequency transceiver circuit  120  and radio frequency transponders  105  is substantially continuous, item updated images can be presented on display screen  175  based upon data stored by radio frequency transponders  105  as entry  252  and fields  255 . 
   Referring back to  FIG. 1 , when a consumer moves or parks his shopping cart  170  in front of the shelf tag  101   e , control circuit  140  prepares an image that presents information regarding a plurality of unique items  107   d ,  107   e  and causes this image to be displayed as shown in the example of display screen  175  in  FIG. 3 . 
     FIG. 3  shows an exterior view of one embodiment of a portable item information device  150  presenting an image  276  that is the result of the transmission interaction between radio frequency transceiver circuit  120  and radio frequency transponder  105   e  corresponding to Vendor E&#39;s tomato soup, and between radio frequency transceiver circuit  120  and radio frequency transponder  105   d  corresponding to Vendor D&#39;s tomato soup. The exchange of interrogation signal  210  and responsive signal  215  results in the generation of image  276  based upon data that was previously stored by corresponding radio frequency transponder  105  in entry  252  and fields  255 . 
   Shopping cart  170  can be moved down aisle  185  at different speeds or linger in front of display shelf  190  and shelf tag  101  for different periods of time. Regardless of the speed movement, as shopping cart  170  is moved through aisle  185 , radio frequency transceiver circuit  120  is brought into a proximate distance with different shelf tags  101  along aisle  185  and image  276  presented on display screen  175  reflects unique items  107   d ,  107   e  within the proximity distance of shopping cart  170  and radio frequency transceiver circuit  120 . As shopping cart  170  is further moved along aisle  185 , radio frequency transceiver circuit  120  is brought into proximity with different unique items  107  and different shelf tags  101 , and control circuit  140  can adjust image  276  to reflect such newly proximate items. 
   Such movement also adjusts the position of proximate distance so that radio frequency transponders  105  previously detected, are now outside of the proximate distance since their shelf tags  101  are now beyond the distance where transceiver circuit  120  will receive a responsive signal  215  from radio frequency transponder  105 , when radio frequency transceiver circuit  120  does not sense previously detected shelf tags  101 , control circuit  140  will adjust the appearance of image  276  so that it is no longer based upon item information from transponders  105  on such shelf tags. 
   As shown in  FIG. 3 , regardless of the structure upon which the invention is incorporated, once image  276  is presented on display screen  175 , the user may manipulate the viewable image  276  by performing a number of operations on the information. For example, a user may use scroll-up bar  277  and scroll-down bar  278  and then the select key  280  to store a displayed item in memory for later recall to determine a running total of the price of goods selected for purchase by using the total key  282 . Additionally, one or more sections of image  276  can be selected using select key  280  and operated upon using programmable hot keys  281  to store and track information to provide a total number of calories for a consumer planning a menu. Image  276  can be displayed on display screen  175 , and programmable hot keys  281  can be programmed by the seller of goods or by the user to provide consumers&#39; with manipulation options to further enhance the shopping experience and to provide valuable information. For example, responsive signals may be received from a radio frequency transponder associated with a shopper prior to beginning the shopping journey through a store. The radio frequency identification input from the shopper can be used to upload a shopping list or a list of favorite items or additional information unique to the shopper. This type of external input can be facilitated through the use of programmable hot keys. Keyboard  283  can be used to provide input to assist in setting up programmable hot keys  281  and to otherwise edit information shown on display screen  175 . 
   In this fashion, a consumer could use display screen  175  to view a running total of the price of items selected, a running calorie count for items selected, or as a display point to compare any information presented by display screen  175  with stored information pertinent to items the consumer is considering for purchase. 
     FIGS. 4A ,  4 B, and  4 C show an example of radio frequency transponders  105  in shelf tags  101  that come within a proximate distance  299  (shown by dotted line around shopping cart  170 ) of radio frequency transceiver circuit  120  in a portable item information device  150 . For clarity, reference numerals are shown in  FIG. 4A  only, and  FIG. 4B  and  FIG. 4C  show the travel of shopping cart  170  and the corresponding change in proximate distance  299 . The objects depicted in  FIG. 4B  and  FIG. 4C  are identical to those shown and denoted by reference numerals in  FIG. 4A . 
     FIG. 4A  shows shopping cart  170  in an initial position where proximate distance  299  encompasses shelf tags  101   d ,  101   e ,  101   i ,  101   j . In this initial position, radio frequency transceiver circuit  120  transmits radio frequency interrogation signals, and radio frequency transponders  105   d ,  105   e ,  105   i ,  105   j  answer by providing responsive signals as described previously. The responsive signals are detected by radio frequency transceiver circuit  120  indicating the presence of shelf tags  101   d ,  101   e ,  101   i ,  101   j . Image  276  is presented on display screen  175  based upon these responsive signals from shelf tags  101   d ,  101   e ,  101   i ,  101   j . Since shelftags  101   a ,  101   b ,  101   c ,  101   f ,  101   g ,  101   h  are beyond proximate distance  299 , radio frequency transponders  105   a ,  105   b ,  105   c ,  105   f ,  105   g ,  105   h  do not receive interrogation signals, do not generate a responsive signal, or alternatively do not generate a responsive signal that can be sensed by radio frequency transceiver circuit  120 . 
     FIG. 5A  shows an example image  176  corresponding to the shopping cart position shown in  FIG. 4A . In the example illustrated in  FIGS. 4A and 5A , unique item  107   e  is a can of Vendor E tomato soup, while unique item  107   d  is a can of Vendor D tomato soup. Additionally, proximate distance  299  also encompasses the other side of aisle and thereby receives data from radio frequency transponders  105   i ,  105   j  located in shelf tags  101   i ,  101   j . While these unique items  107   i ,  107   j  may be of a completely different food group and genre, since these radio frequency transponders  105   i ,  105   j  respond to an interrogation signal from radio frequency transceiver circuit  120 , image  276   a  also reflects these items as well as shown in  FIG. 5A . 
     FIG. 4B  shows shopping cart  170  in an intermediate position as it is moved further along aisle  185 . Since shopping cart  170  is now in a new position, proximate distance  299  now encompasses shelf tags  101   c ,  101   d ,  101   h ,  101   i . In this intermediate position, radio frequency transceiver circuit  120  transmits interrogation signals, and radio frequency transponders  105   c ,  105   d ,  105   h ,  105   i  answer by providing responsive signal that are detected by radio frequency transceiver circuit  120  indicating the presence of shelf tags  101   c ,  101   d ,  101   h ,  101   i . Control circuit  140  determines new output information based upon item data in responsive signals detected by radio frequency transceiver circuit  120  from radio frequency transponders  105   c ,  105   d ,  105   h ,  105   i . An image  276   b  is then prepared by control circuit  140  based upon this output information and image  276   b  is shown on display screen  175 . Since shelf tags  101   a ,  101   b ,  101   e ,  101   f ,  101   g ,  101   j  are now beyond the proximate distance  299  of radio frequency transceiver circuit  120 . Radio frequency transponders  105   a ,  105   b ,  106   e ,  105   f ,  105   g ,  105   j  do not receive interrogation signals, do not generate a responsive signal or, alternatively, they do not answer in a manner that radio frequency transceiver  120  can sense. 
     FIG. 5B  shows an image  176   b  presented on display screen  175  corresponding to the shopping cart position shown in  FIG. 4B . In the example illustrated in  FIGS. 4B and 5B , unique item  107   c  is a can of Vendor C chicken-noodle soup, while unique item  107   d  is a can of Vendor D tomato soup. Additionally, proximate distance  299  also encompasses the other side of aisle  185  and thereby receives data from radio frequency transponders  105   h ,  105   i  located in shelf tags  101   h ,  101   i . While these unique items  107   h ,  107   i  may be of a completely different food group and genre, since these radio frequency transponders  105   h ,  105   i  respond to interrogation signals from radio frequency transceiver circuit  120 , viewable image information  176   b  is also generated and displayed based upon the detected presence of these items as well as shown in  FIG. 5B . 
   Finally,  FIG. 4C  shows shopping cart  170  in a final position as it is moved further along aisle  185 . Since shopping cart  170  is now in a new position, proximate distance  299  now encompasses shelf tags  101   b ,  101   c ,  101   g ,  101   h . In this position, radio frequency transceiver circuit  120  transmits interrogation signals, and radio frequency transponders  105   b ,  105   c ,  105   g ,  105   h  answer by providing data in the form of an output signal. Responsive signals detected by radio frequency transceiver circuit  120  are then used to form an image  276   c  which is then presented on display screen  175 . Since shelf tags  101   a ,  101   d ,  101   e ,  101   f ,  101   i ,  101   j  are now beyond the proximate distance  299  of radio frequency transceiver circuit  120 , radio frequency transponders  105   a ,  105   d ,  105   e ,  105   f ,  105   i ,  105   j  do not receive interrogation signals, do not generate a responsive signal or alternatively, do not generate a response signal that can be sensed by radio frequency transceiver circuit  120 . 
     FIG. 5C  shows image  276   c  presented on display screen  175  when shopping cart  170  is positioned as shown in  FIG. 4C . In an example illustrated in  FIGS. 4C and 5   c , unique item  107   b  is a can of Vendor B chicken-noodle soup, while unique item  107   c  is a can of Vendor C chicken-noodle soup. Additionally, proximate distance  299  also encompasses the other side of aisle  185  and thereby receives data from radio frequency transponders  105   g ,  105   h  located in shelf tags  101   g ,  101   h . While these unique items  107   g ,  107   h  may be of a completely different food group and genre, since these radio frequency transponders  105   g ,  105   h  respond to an interrogation signal from radio frequency transceiver circuit  120 , image  176   c  reflects these items as well, as shown in  FIG. 5C . 
   As may be apparent from the above example, and as discussed above with regard to transmission power and reception sensitivity, the orientation of antennae in radio frequency transponder  105  and radio frequency transceiver circuit  120  may be modified to alter the shape, direction, and distance of proximate distance  299  to optimize the exchange of interrogation signals and responsive signals indicative of item information and characteristics of unique items in the store. By modifying the shape and size of proximate distance  299 , different retail establishments may optimize displays based upon consumer preferences, relative sizes of items and display shelves, width of aisles, and any number of other variables in a sales environment. 
   Additionally, portable item information device  150  can be mounted in structures other than shopping carts to permit users more freedom of movement in a sales environment. For example, portable item information device  150  may be mounted in a plastic shopping basket or incorporated in a handheld device such as a personal digital assistant or other mobile computing device. 
   The invention has been described in detail with particular reference to certain preferred embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
   PARTS LIST 
   
       
         100  sales environment 
         101  shelf tag 
         101   a - 101   j  shelf tag 
         105  radio frequency transponder 
         105   a - 105   j  radio frequency transponder 
         106  shelf space 
         106   a - 106   j  shelf space 
         107  unique item 
         107   a - 107   j  unique item 
         120  radio frequency transceiver circuit 
         135  memory 
         140  control circuit 
         144  remote server 
         150  item information device 
         170  shopping cart 
         175  display screen 
         176  display image 
         176   a - 176   c  display image 
         185  aisle 
         190  display shelf 
         210  interrogation signal 
         215  responsive signal 
         215   a - 215   c  responsive signal 
         245  database 
         250  record 
         252  entry 
         255  field 
         276  image 
         276   a - 276   c  image 
         277  scroll-up bar 
         278  scroll-down bar 
         280  select key 
         281  hotkey 
         282  total key 
         283  keyboard 
         299  proximate distance