ITF (Interleaved 2 of 5)
The Interleaved 2 of 5 (or ITF) code was developed from an earlier symbology called simply Code 2 of 5. Code 2 of 5 is numeric and has bars which can be wide or narrow. Spaces carried no information, and therefore their width was not critical.
The Interleaved 2 of 5 symbology was suggested as a way of shortening the length of the code by using the spaces to carry information. Data is encoded in pairs of digits with the bars representing the first character of a pair and the spaces representing the second character.
The ratio of narrow bar width to wide bar width can be between 2:1 and 3:1 but in the UPC and EAN specifications for 14 digit shipping (or traded unit) symbols it is fixed at 2.5:1 and this has become the norm.
Interleaved 2 of 5 was chosen for the standard outer carton bar code because it's printed tolerances are sufficient for the highly variable printing techniques used for corrugated cartons.
At the standard 100% magnification, the amount of variation allowed in bar width is 0.3mm (0.012").
The above example shows the standard human readable character grouping for the European traded unit code.
The EAN and UPC versions of 14 digit ITF case codes use the same check digit calculation as described in the section on the EAN symbology.
Outside of the outer case coding environment, Interleaved 2 of 5 is used for a number of bar coding applications with varying lengths of code.
It should be noted that where variable length ITF symbols are used without a check digit, there is a danger of the scanner misinterpreting a partially scanned code as a complete code. Therefore when using ITF the scanner should be programmed to expect a fixed length of code or a check digit.
Because of the imprecise nature of corrugated carton printing, ITF bar codes often employ a bearer bar around the code to protect the symbol from excessive plate squash. Three differing types of bearer bar are used:
It is also common for ITF symbols to carry "H-Gauges". These offer a quick visual check of print quality.
There are seven variations of H-Gauge, each having a different distance between the vertical bars. Dependent on the magnification factor of the code being printed and the amount of print gain expected, two H-Gauges may be selected, one of which should always fill-in within the vertical bars, the other should remain clear. If both fill in, the printing plate may need to be cleaned or the pressure on it reduced. If both gauges remain clear, there may be insufficient pressure on the plate or an error in plate manufacture.
Bar Code Uses
Bar Code Structures
Getting a Good Scan
PostScript Imaging of Bar Codes
ITF (Interleaved 2 of 5 )
Glossary of Bar Code Terms