How Bar Codes Work

A printed bar code is a machine readable code representing a set of numbers or characters. It is made up of thick and thin parallel bars. Certain combinations of thick and thin bars represent a number or character in much the same way as dots and dashes represent specific letters and numbers in Morse code. However, in a bar code, the width of the spaces between the bars also plays a role.

A set reference combination marks the start and end of the code, so the scanner's software can interpret the code correctly even if the label is upside down.

The scanner uses a rapidly oscillating mirror and a laser to 'scan' the bar code. A light sensitive device in the scanner records the varying amount of light reflected back from the bars and spaces, and software converts this into a number or character set which can be used to identify the product or item from a data-base.

A bar code printer uses software to convert a given number or character set into a bar code and produce a bar code label. There are many international standard types of bar code or 'symbologies' which cater for differing amounts or combinatons of data. They have been adopted by various industries to ensure conformity, for example, on airline baggage labels which must be recognisable by different tracking systems around the world. 1D Bar Codes One dimensional bar codes, similar to those which appear on supermarket and retail products, are the key to complete stock and price control as well as comprehensive asset tracking systems. The code will be unique to a particular product or package. The bar code wand or scanner reads the code and the resulting data is used to identify the item in the system database.

2D Bar Codes Two dimensional bar codes or 'Matrix' codes, work in much the same way but contain significantly more data. They are made up from complex patterns of dots or circles and are read by a scanning device which looks like a bar code scanner but is actually an image capturing camera. 2D bar codes enable an operative with the correct scanning device to access full data about the item such as product description, manufacturing specifications, its sender and the delivery address.