The basic principles of barcodes A unique bar coding system has been developed for all Royal Mail sorting machines. It is capable of containing large amounts of data, and can be produced by all types of printing systems. Each ‘character’ consists of four bars.Two of these have ascenders and two have descenders.There is also a track element in all bars.
How it works CBC – Customer Bar Coding – means printing a barcode on the item, as well as the correct address and Postcode. The barcode gives the machines the exact information they need to sort the item for delivery. Mail with a correctly prepared and printed barcode passes swiftly through the machines, and as there are fewer ‘reading’ problems, are rarely rejected and defaulted to manual sorting.
There are 38 valid characters:
• Numbers 0-9. • Letters A-Z. • Open and close brackets: (–).
A typical complete barcode A complete customer barcode consists of:
• A start bar, positioned at the normal left hand end, next to the first significant data character. • A set of ‘characters’ (each consisting of distinct bars and spaces) which give the Postcode (outward code then inward code). • Two characters (a number plus a letter) which give the Delivery point suffix (DPS). • A checksum character.This helps us spot errors. These are explained below. • A stop bar, at the normal right hand end of the complete code next to the checksum character. See the illustration below.These elements should only be printed in barcode format, and are in addition to the normal address and Postcode.
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