RM4SCC ( Royal Mail 4 State Customer Code ) is a standard developed by the Royal Mail in the UK bar code.
The RM4SCC was developed in the UK by the Royal Mail, but is now also in other countries ( Switzerland, Austria, Denmark, Australia ), but use different definitions of the characters or build the code differently. The Universal Postal Union has also issued corresponding specifications.
Structure and properties
Every single line assumes one of four states (german 4 state), thus encodes two bits. The four possible states are shown in the examples on the right. In each case, four lines form a group of eight bits, or one byte and encode a character.
The arrangement of the printed characters is defined in both directions. That the code needs both in the transport direction conform to the specifications as well as perpendicular to it. In practice, this means that at least sharp vertical bars must be printed. In addition, the aspect ratios are given for most codes.
At very high speeds (for example, in the letter sorting 3.5 m / s) it is not possible to include direct to realize, for example, by means of inkjet printers within the tolerances. In general, lines are distorted and bent, which is due from the low flight time between generation of a point and the impact on the fast-moving surface pressure. Thus, the tolerances for 2- dimensional codes are typically no longer maintained or the codes need to be small ( amount of data and reading reliability low).
The RM4SCC is particularly suitable for very high speeds with direct pressure, since it tolerates distortions largely. The example shows a distorted code. He is still easily readable as is present in every stroke of the tracker. The reading technique uses as a trigger to decide whether above or below something was printed. The problem arises when the individual lines run into each other, since the clock of the tracker is then hard to find. Also sloping line codes are much harder to read, since only the center line is to be sought with the tracker then from the overall picture. The specifications of the code therefore define appropriate tolerances.