Datalogic Hand-held devices II Specifikace stáhnout pdf (Strana 14)

Page1 AllAboutBarCodes

Backup Hardware: As a system is integrated into a process, it will gradually become more critical Try to have backup

hardware somewhere to take care of the inevitable failure In many cases, you can keep a spare PC in use for another

purpose as long as it can be quickly brought on line in case of a failure Be sure to keep the software on the spare PC up

to date so that it can be switched quickly Insist the company purchase a tape backup system and schedule it for automatic

daily backups

Utilities: When you install a system, take care to include diagnostic and troubleshooting utilities to take care of inevitable

problems You should always include some disk and virus-detection utilities

Bar Code Symbologies

Bar code systems can use several symbologies A symbology is equivalent to a language Each symbology has strengths and

weaknesses Many symbologies persist for historical or commercial reasons, while others have denite technical advantages

In many systems, you must conform to a company or industry specied symbology If this is the case, then you don’t have

much choice unless you can give the company a good reason to change In other systems, you are given the choice to use any

symbology you wish Choose your symbology carefully There are several factors to use in choosing a symbology, including:

Character Set: All symbologies have some limitations on the number and type of characters that can be encoded

(numeric/alphabetical) UPC-A (Universal Product Code) is the most limiting It is a numeric-only bar code that must consist

of 12 digits Furthermore, the value of these digits is determined by standards managed by the Uniform Code Council (UCC)

in North America, and by EAN International in the rest of the world Code 128 is the most exible, with the full (128-character)

ASCII set available

Standards: Many bar code applications must share common bar codes between different vendors The EAN/UCC system

has assigned unique UPC Company Prexes for well over one million product manufacturers That is the reason that a

product manufacturer can put a bar code on a package without fear of duplication If you are in a situation where some

type of industry committee has set up standards, it is frequently in your best interest to conform to that standard, even if it

imposes other limitations

Density: Each symbology can encode a different number of characters in a given space with all other factors being the

same In many cases this is critical Even if one symbology is capable of making a bar code of the required size, you may get

a better rst read rate using a different symbology

Feature Size: Note that some scanners, particularly wands, are designed to optimally read bar codes with a specic range

of widths of the bars and spaces that make up the bar code Make sure that your reading device matches the feature size

of the bar code you will use

Readability: Some bar codes are inherently more readable than others For example, tests show that Code 128 (which is

one of the most exible symbologies) is easily and successfully read by most readers This is a case where the symbology

is better in nearly every way than the competition In other cases, you may sacrice readability for some other requirement

Always use the most readable symbology you can, and test it using the actual equipment you plan to use

Fault Tolerance: Some symbologies are more fault tolerant than others, that is, more tolerant of damage to the printed bar

code As a rule of thumb, those with better readability are more fault tolerant than others You should always test your bar

codes by subjecting them to some abuse and making sure your equipment will still read them

Acceptance: Your bar codes may need to be compatible with those of companies you do business with Whenever

possible, use symbologies that are already in place

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Datalogic Hand-held devices II Specifikace Strana 14