When a barcode scanner reads the Function 1 character, it knows that the barcode follows GS1 rules and that it should look for the data elements that are defined by GS1 standards.
The FNC1 is encoded at the start of the symbol, ahead of the first Application Identifier (AI).
Below is an illustration of the FNC1 (highlighted in blue) in a GS1-128 barcode.
Data separator
The Function 1 character can also be used as a data separator. If the barcode contains non predefined length data elements, such as serial or batch numbers, the FNC1 is used to signify that the field has ended, so the scanner can then look for the next piece of encoded data.
For data elements that have a fixed length, such as a GTIN or dates, the Function 1 character is not needed.
The barcodes most used by GS1 UK members that require the Function 1 character are the GS1-128 and GS1 DataMatrix . If the FNC1 wasn’t encoded within the symbols then they would be code 128 and data matrix barcodes respectively, and these barcodes are not GS1 compliant.
Encoding the Function 1 Character
Encoding the FNC1 character in a barcode depends on the specific barcode symbology and the software you are using to generate the barcode. When encoding AIs, the FNC1 character is often included automatically by barcode software to separate non-pre-defined length. Otherwise, you might need to adjust the settings or consult your software provider's customer service.
Whatever you do, after encoding, it is recommended to always test the barcode to ensure that the FNC1 character is correctly interpreted and that the barcode conforms to GS1 standards.
For full technical requirements around the FNC1, including which AIs require the FNC1 character, refer to the GS1 General Specifications, Section 3 GS1 Application Identifier definitions.