Beckman Coulter COULTER LH 750 System, Справочник

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PN 4277248DD
4-15
SPECIFICATIONS/CHARACTERISTICS
BAR-CODE SYMBOLOGY OVERVIEW
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A symbology is defined by the following characteristics:
Character Set
This refers to the range of data characters that can be encoded for a specific symbology. There
are essentially three types:
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Numeric—The symbology can encode only numeric characters.
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Alphanumeric—Can encode the full alpha and numeric characters of the ASCII
character set.
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128—Can encode all the 128 available ASCII characters.
Symbology Type
There are essentially two types:
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Discrete—Each character is separated from the next by an intercharacter gap. This allows
each character to be decoded independently. Every character has a bar on each end.
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Continuous—Has no intercharacter gaps. Every character begins with a bar and ends
with a space.
Fixed or Variable Length
Some symbologies can only encode messages of a fixed length. Some can be used to encode
variable length data. Some should only be used as a fixed length to increase the security of
data decoding.
Self-Checking
A self-checking symbology has the ability to prevent character transposition due to a single
printing defect.
Start Code, Stop Code
Start and Stop Codes are bar and space patterns that are placed at the beginning and end of
the encoded data. A start code indicates the beginning of the symbol, and indicates the start of
the encoded information. The stop code indicates the end of the symbol and marks the end of
the encoded information.
Check Character, Checksum Algorithm
Virtually all bar-code symbologies use a check character. The check character is derived by a
mathematical calculation using the characters in the encoded information. It is used by the
scanning device to verify that the correct information has been decoded. It is highly
recommended that a check character, also called a checksum algorithm, is used.
Quiet Zone, Quiet Area
The Quiet Zone is a clear area on either side of the start and stop codes. It helps the scanning
device establish the reflectivity characteristics of the label.