The Interleaved 2 of 5 barcode forms the basis of the German Identcode and Leitcode symbols used by Deutschen Post. These are 12 and 14 digit barcodes respectively, but they do use a different Mod 10 check digit calculation from the standard I-2 of 5 symbol.

Checking the EXTRA1 checkbox in applications, or setting the flags parameter bit DL_FLAG_EXTRA1 (bit 4 of the flags variable) turns on the Deutschen Post check digit when auto-check digit is also on, enabling the I-2 of 5 barcode image to be used as Identcode and Leitcode symbols.
Note that spaces and periods are removed from the strings supplied for I-2 of 5 barcodes before the barcode image is created – so the correct layout for Identcode and Leitcode text may be used to create the symbols.
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