Blahut was pleased with the unexpected delivery, nonetheless. A series of irregular-length pink bars printed just below the three Queen Elizabeth postage stamps caught his eye. At last, Blahut was seeing his encoding technology in use. According to the Royal Mail, the 4-state code technology has reduced the error rate from .5 percent under the old system to .0000005 percent. Five years ago, the Royal Mail decided to replace its existing bar coding system to improve the way it automatically sorts the more than 18 billion items of mail it handles each year.
Bar codes contain important sorting and delivery information.
If the printed address is legible, a bar codemark is applied to the mail so it can be automatically sorted and delivered to its final destination. Although there were existing technologies on the market, the Royal Mail opted to develop its own code. In an article in the Royal Mail's May 1994 Automation magazine, Senior Technical Manager Greg Hopkins said Royal Mail ruled out the U.S. Postal Service's bar code along with Code 39, which is similar to the bar code scheme used on supermarket products. However, information is encoded by varying the width of the bars, so it has to be printed accurately to have any chance of being read. Given the letter transport speeds of our machines and the performance of ink jet printers, it would be unrealistic to use Code 39.