When documents containing bar belief symbols are faxed, the superior of the bar belief badge will lower. Documents scanned by fax machines in Standard Resolution are sampled next to 204 crosswise dots per in and 98 plumb dots per linear unit. Each sample barb is later converted to either a light-colored or achromatic numerical quantity (a course of action noted as binarization). The binarization course of action converts nonstop lines of the bar codification symbols into old lines shifting the breadth of the gymnastic apparatus and spaces. If a faxed papers is itself dislike out as a fax, more relapse occurs. Each further fax round continues to confound the bar belief. At both point, the pictograph may no long be able to be decoded by bar written language decoding software.

The rest of this piece will talk about the issues that should be thoughtful when selecting bar attitude symbologies and sizes to heighten the odds of successful decodes after quaternary fax cycles.

Linear (1D) Symbologies

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Two favourite 1D symbologies were examined: Code 128 and Code 39. Code 128 uses iv bar and universe widths to inscribe information, spell Code 39 sole uses two. Thirteen faculty sizes (smallest item) travel from 12.5 mil to 32.5 mil of all signal type, secret writing ten definite quantity digits, were written on a sheet. The sheet was sent through a fax at Standard Resolution for a total of ten cycles. This corresponds to a flat representative per ability move from 2.6 to 6.6. The resulting 11 pages were later scanned on a flatbed referee at 300 samples per linear unit and were given to a bar secret message translate software toolkit. At 2.6 samples per mental faculty both bar secret message symbologies were just able to be successfully decoded for 3 faxes time the same codes near 6.6 samples per ability were stationary readable after 10 faxes.

The larger samples per ability (6 samples and greater) were able to gleefully work out after 10 fax cycles. At 5.6 samples per module, the decipher working was no higher than 4.6 pixels per module. This demonstrates that respectively fax time interval alters the bar written language in a impalpable way. Every fax time interval produces a unusual interpretation of the inspired bar code, and all change can form a badge that did not publication after a infallible figure of fax cycles publication on the side by side one. However, if illustrious publication tax are desirable after oodles fax cycles, next printing the bar belief symbols at a borderline of 6 samples per module is advisable.

From the trialling conducted, Code 128 somewhat outperformed Code 39 after quadruple faxes. Given the higher notes firmness of Code 128 and the built in checksum, Code 128 appears to be a better prize concerning the two symbologies. The similes at a lower place live entertainment the magnitude lead of Code 128 over Code 39, next to both symbols cryptography 10 numerical digits with the aforementioned module vastness. If the aggregation to be encoded is strictly numeric, the numeral compression property of Code 128 can be nearly new to added heighten accumulation density.

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There is a trade off to consider: the large the mental faculty massiveness of a additive code, the more than level room will be essential to write the aforesaid amount of information, but the large modules sizes can remodel publication rate. One superfluous cause to believe is the bar standard distance from the ground. For this test, all the codes were ½ linear unit in height above sea level. Given that all plumb figures in 1D bar codes is by explanation redundant, if area allows, raising the height of a bar written communication will typically donate amended publication taxation after septuple fax cycles.

Matrix (2D) Symbologies

Matrix symbologies give dramatically in good health hearsay compactness because rumour is encoded in both naiant and upright directions. Given their sized supremacy complete their additive counterparts, 2D symbols can be written next to untold larger mental faculty sizes and yet be equal to bilinear symbols encoding the same content. For the 2D test, we printed varied sizes of Data Matrix and Micro QR Codes. The Data Matrix was a 12 x 12 faculty squared badge. The Micro QR is a more area streamlined revision of a QR symbols that employs only one searcher model and is restricted to a cipher of littler sizes. The symbols were encoded at a comparable plane of lapse rectification. The mental faculty sizes varicolored from 39 mil to 79 mil. Like the 1D test, we subjected the representation to 10 fax cycles and next scanned the metaphors. The metaphors were scanned at 150 samples per linear unit specified the sizeable characteristic sizes of the try-out bar codes. The scanned metaphors were next processed by the same bar written language coding toolkit.

At 8.7 samples per mental faculty the 2D bar codes were competent to be publication after 5 fax cycles and former 15 samples per mental faculty were reached the codes were legible up to 10 cylces.

The results were not as regular as the 1D symbols. This is due to the certainty that the wilful misunderstanding of the figure of speech during the escalating figure of fax cycles affects aggregation in some the collection dimensions. However, we can gully the achievement that symbols near large volume modules will make out more than faithfully after eightfold fax cycles.


If documents containing bar written communication symbols are to be faxed double times, the bar written communication symbols must be printed near bigger module sizes to be elatedly decoded.

For additive symbologies, if a huge number of fax cycles (greater than 5) is required, the amount of samples per faculty should be at smallest 6. Code 128 performed good in our tests and has a high data firmness than Code 39. Linears are a pious choice for coding wee amounts of assemblage.

For bigger background requirements, 2D symbologies such as as Data Matrix, stock swell order public presentation after faxing if larger module sizes are utilized. They stock the added skill of reduction the magnitude of genuine holding unavoidable in the submission document due to their first-class information compactness.

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