Hand Held Products IT4800 Bar Sequence, Codeword Data and Check, Codeword Yield, Edge Accuracy

Bar Sequence

Bar Sequence is the bar height pattern within a height modulated, multi-state, postal-type symbology. In a 2-state symbol, a "1" represents a tall or full height bar and a "0" represents a short or half height bar. In a 4-state symbol, "A" rep- resents the ascending bars, "D" the descending bars, "T" the short bars, and "H" the tall bars that both ascend and descend. Incorrect sequencing can be sys- tematic and can be caused by the symbol generating program not meeting requirements.

Codeword (Data and Check)

A Codeword is a symbol character value or intermediate level of coding between source data and the graphical encodation in the symbol. A data code- word encodes data according to the rules or scheme of the symbology, where check codewords are reserved for error detection/correction purposes.

Codeword Yield

Codeword Yield is an indication of the interference between adjacent rows in a 2D stacked symbology. A low Codeword Yield can indicate print conditions where this interference is caused by drag, streaking, or other situations where there is carry-over of ink from one row to another (see "Useful Row Height" on page 1-19).

Data Safety Margin

Data Safety Margin is the ratio of the unused error correction codewords to the recommended number of error correction codewords. A low Data Safety Mar- gin indicates a symbol that is close to reading failure and can be improved by improving the printing, correcting the cause of bad or missing symbol characters (e.g., spots, voids), or by raising the Error Correction Level (ECL).

Edge Accuracy

Edge Accuracy is a measure of the accuracy of the bar or dark element edge positions within the symbol. A low Edge Accuracy indicates print conditions, such as a "print pitch to X-dimension" mismatch or general edge irregularities (but not uniform print growth), which can harm character decoding. The first condition is improved by properly scaling the symbol to the print pitch, and both conditions are improved by making the symbol larger.

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