How Interleaved 2 of 5 works
Interleaved 2 of 5 encodes digits in pairs: the first digit of each pair is carried by the bars and the second by the spaces between them. Each digit uses five elements, two of which are wide. Because digits come in pairs, the data always has an even number of digits, which suits the 14-digit GTIN.
ITF is specified in ISO/IEC 16390. ITF-14 is the GS1 application of it for trade items that do not pass through a retail checkout.
Why cartons use ITF-14
ITF-14 tolerates the rough, low-resolution printing typical of corrugated boxes. The bearer bars, a heavy frame or bars above and below the symbol, spread the pressure of printing plates and help prevent a short read where a scanner sees only part of the code.
The 14 digits start with an indicator digit that distinguishes packaging levels, followed by the digits of the related GTIN and a recalculated check digit. For example, a case of 12 jars and the single jar get different GTINs.
- Length: 14 digits
- Indicator digit: 1 to 8 for packaging levels, 9 for variable-measure items
- Bearer bars: usually a frame or top and bottom bars
- Common place: outer cases and shipping cartons