INTERLEAVED 2 OF 5 SYMBOLOGYSee Also:    Standard 2 of 5    Symbology Index
INTERLEAVED 2 OF 5 BACKGROUND INFORMATIONInterleaved 2 of 5 is a higher-density numeric symbology based upon the Standard 2 of 5 symbology. It is used primarily in the distribution and warehouse industry.
Interleaved 2 of 5 encodes any even number of numeric characters in the widths (either narrow or wide) of the bars and spaces of the bar code. Unlike Standard 2 of 5, which only encodes information in the width of the bars, Interleaved 2 of 5 encodes data in the width of both the bars and spaces. This allows Interleaved 2 of 5 to achieve a somewhat higher density.
The symbology is called "interleaved" because the first numeric data is encoded in the first 5 bars while the second numeric data is encoded in the first 5 spaces that separate the first 5 bars. Thus the first 5 bars and spaces actually encode two characters. This is also why the bar code can only encode an even number of data elements.
A typical Interleaved 2 of 5 bar code is:
COMPUTING THE CHECKSUM DIGITInterleaved 2 of 5 is similar to Standard 2 of 5 in the sense that it may include an optional modulo 10 check digit. Please see the section concerning Computing the Checksum digit in the Standard 2 of 5 page. The process for calculating the check digit is the same in Interleaved 2 of 5 as it is in Standard 2 of 5. And, like Standard 2 of 5, the checksum digit is optional.
ENCODING THE SYMBOLIn the following text, we will discuss the encoding of the bar code by considering that the number "1" represents a "dark" or "bar" section of the bar code whereas a "0" represents a "light" or "space" section of the bar code. Thus the numbers 1101 represents a double-wide bar (11), followed by a single-wide space (0), followed by a single-wide bar (1). This would be printed in the bar code as:
STRUCTURE OF AN INTERLEAVED 2 OF 5 BARCODEAn Interleaved 2 of 5 bar code has the following physical structure:
INTERLEAVED 2 OF 5 ENCODING TABLEThis table indicates how to encode each digit of an Interleaved 2 of 5 bar code. Note that the encoding is expressed as "N" (narrow bar or space) or "W" (wide bar or space).
ENCODING EXAMPLEWe will now code the above example in Interleaved 2 of 5: "12345670". By this point we would already have calculated the checksum digit as "0" (the last digit of the bar code value) as illustrated in the checksum calculation section illustrated above.
Now we need to encode each digit using the encoding table above:
For example, in the case of the first two digits "12", we encode the "1" in the bars using the sequence WNNNW (Wide bar, narrow bar, narrow bar, narrow bar, wide bar). We encode the "2" in the spaces that separate the bars of the first digit. The digit "2" is encoded in spaces with the sequence NWNNW (narrow space, wide space, narrow space, narrow space, wide space).
Assuming "1" is a narrow bar, "11" is a wide bar, "0" is a narrow space, and "00" is a wide space, the above would be encoded as follows:
The process for the rest of the pairs of characters is the same. It results in the following:
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