Invention and Engineering

Barcode

A barcode or bar code is a method of representing data in a visual, machine-readable symbolic form. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines. These barcodes, commonly referred to as linear or one-dimensional (1D), can be scanned by optical scanners known as barcode readers. Later, two-dimensional (2D) variants were developed, using rectangles, dots, hexagons and other patterns, called matrix codes or 2D barcodes. Despite being often included as barcodes, these do not use bars as linear barcodes do. These can be read using purpose-built 2D optical scanners. Both matrix codes and linear barcodes can also be read by a digital camera connected to a computer. After a photograph of the barcode is taken, software is used to analyze the image to deconstruct and decode the code. A mobile device with a built-in camera, such as a smartphone, can function as this type of barcode reader using specialized application software. The barcode was invented by Norman Joseph Woodland and Bernard Silver and patented in the US in 1952. The invention was based on Morse code that was extended to thin and thick bars. However, it took over twenty years before this invention became commercially successful. UK magazine Modern Railways December 1962 pages 387–389 record how British Railways had already perfected a barcode-reading system capable of correctly reading rolling stock travelling at 100 mph (160 km/h) with no mistakes. An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s. Developed by General Telephone and Electronics (GTE) and called KarTrak ACI (Automatic Car Identification), this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock. Two plates were used per car, one on each side, with the arrangement of the colored stripes encoding information such as ownership, type of equipment, and identification number. The plates were read by a trackside scanner located, for instance, at the entrance to a classification yard, while the car was moving past.

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See also

• ▸Incandescent light bulb
• ▸Huarpe
• ▸Electronics in rock music

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