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How does an electronic price scanner work? 

This may have been one of the questions then President George Bush had in mind when he was widely reported to have been amazed by the existence of commercial price scanners while on the campaign trail in 1992. While these reports fueled significant discussion during the campaign because price scanners had existed for nearly 20 years at that point in time, later accounts indicate that President Bush was amazed at the state of the technology rather than the existence of it.

The history of the modern price scanner goes back more than 50 years, when Bernard Silver and Norman Woodland devised a system for marking and identifying objects. This system had its roots in two established technologies of the time: Morse code and DeForest's movie sound system. Silver and Woodland extended the dots and dashes of the Morse code vertically to create a pattern of varying width bars. They used these bars to encode data in a manner similar to DeForest's technique for recording sound as a varying pattern on movie film. Silver and Woodland received their patent in 1952, but it wasn't until 1974 that the first product -- a pack of gum -- was sold using a modern price scanner.

Today, most products sold in the U.S. are marked with a barcode called a Universal Product Code, or UPC. The UPC is a 12-digit code that identifies the category of the item (normal items, items sold by weight, pharmaceuticals, items unique to the store, and coupons), the manufacturer, and the manufacturer's item number. The UPC consists of machine-readable bars, as envisioned by Silver and Woodland, and human-readable numbers. The price scanner in your grocery store interprets the bars of the barcode; the numbers serve as a backup in case the barcode is damaged.

The price scanner "reads" the barcode by sweeping a laser across the bars and measuring the amount of light reflected off the UPC. The price scanner can recognize the bars in the barcode because the dark bars reflect less light than the white spaces between them. The price scanner in your grocery store uses a multifaceted, rotating mirror and several fixed mirrors to sweep the laser across the scanning area in a complex scanning pattern. This pattern is designed to detect the barcode regardless of orientation. This allows the cashier to move items across the scanning area quickly, without having to worry about which way the barcode is facing. Once the UPC is read, the price of the item is retrieved from the store's database and inventory figures are adjusted.

All of the product price data is maintained in computer databases in the stores. These databases are updated with manufacturer product information, and prices are adjusted to reflect sales and other price changes. These same databases are used to track sales, maintain inventories, and produce orders for suppliers. Today, some stores even use data collected at the checkout to determine patterns of consumption (what sells, when, where, and in what combinations) and then sell this information back to the manufacturers.

To ensure that UPCs uniquely identify a single product, the Uniform Code Council (UCC), which was formed in 1973, controls distribution of UPCs. At the current rate of consumption, the UCC is projected to run out of unique codes to distribute to manufacturers in the near future. To avoid this situation and to increase compatibility with the rest of the world, the current UPC will be phased out and replaced by the longer European Article Number (EAN) by the year 2005.

While their early worked spawned a system that is ubiquitous today, Silver and Woodland never reaped large financial rewards from their invention. In fact, Silver didn't live long enough to see the first commercial sale back in 1974. Woodland, on the other hand, has seen it all. And in 1992, he was presented the National Medal of Technology by -- as you might have guessed -- President Bush.

This month's Whizard is Bill Wolff, a senior research engineer in the Communications Systems Section of the Automation and Data Systems Division.

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April 15, 2014