The Effects Of Fax Transmission On Bar Code Decoding
Below is a MRR and PLR article in category Computers Technology -> subcategory Web Development.
The Impact of Fax Transmission on Bar Code Decoding
Introduction
When documents containing bar codes are faxed, the bar code quality often suffers. Standard fax machines scan documents at 204 horizontal dots per inch and 98 vertical dots per inch. Each scan point is binarized?"converted to black or white?"altering the bar code's straight lines into jagged edges and changing the bar and space widths. Repeated faxing further degrades the bar code, potentially rendering it undecodable by bar code software.
This article explores considerations for choosing bar code symbologies and sizes to ensure successful decoding after multiple fax transmissions.
Linear (1D) Symbologies
Code 128 vs. Code 39
We evaluated two common 1D symbologies: Code 128, which uses four widths for encoding, and Code 39, which uses two. Thirteen module sizes, ranging from 12.5 mil to 32.5 mil, were used to encode ten numeric digits. These bar codes were faxed ten times at Standard Resolution, resulting in a horizontal sample per module from 2.6 to 6.6.
Upon scanning the faxed documents at 300 samples per inch, it was found that both symbologies could only be successfully decoded for three faxes with 2.6 samples per module. However, 6.6 samples per module remained readable after ten faxes.
Recommendations
Larger module sizes, like six or more samples per module, improved decoding success after ten fax cycles. Code 128, with its higher data density and built-in checksum, slightly outperformed Code 39. It’s advisable to print bar codes with at least six samples per module for better readability after multiple faxes.
There is a trade-off: larger module sizes require more horizontal space but improve readability. Increasing bar code height can also enhance readability, as vertical information in 1D codes is redundant.
Matrix (2D) Symbologies
Matrix symbologies, such as Data Matrix and Micro QR Codes, offer better information density as they encode data both horizontally and vertically. They can be printed with larger module sizes while remaining compact compared to 1D codes.
For testing, various sizes of Data Matrix and Micro QR Codes were printed, with module sizes ranging from 39 mil to 79 mil. After subjecting these symbols to ten fax cycles and scanning at 150 samples per inch, results showed:
- At 8.7 samples per module, 2D codes decodable after five faxes.
- At 15 samples per module, codes remained readable after ten cycles.
However, 2D symbols showed more inconsistency as distortion affects both data dimensions. Nonetheless, larger module sizes increased decoding reliability.
Conclusion
For documents containing bar codes that will be faxed multiple times, print bar codes with larger module sizes to ensure successful decoding.
- Linear Symbologies: For more than five fax cycles, use six or more samples per module. Code 128 offers higher data density than Code 39 and is suitable for smaller data needs.
- Matrix Symbologies: For larger data requirements, use Data Matrix or similar 2D codes with larger modules. They provide better decode performance and save space due to their superior data density.
By following these guidelines, you can maintain bar code readability and accuracy, even after multiple fax transmissions.
You can find the original non-AI version of this article here: The Effects Of Fax Transmission On Bar Code Decoding.
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