Access Control : Installing and using GateKeeper module : Configuration : Advanced features : Prepend setting
 
Prepend setting
 
This setting causes all barcodes scanned to be pre-pended with the prefix specified.
 
Prepend=B44614485
 
This is prepended to scans which do not have a prefix. Then, if a barcode with 889903 is scanned, ScanMan module interprets the barcode as B44614485889903.