HP Linear Barcode Scanner II Programming Reference Manual page 130

Enter/Exit Programming Mode
Code 39 Interdigit Ratio (continued)
$CC3IR07
Code 39 Interdigit Ratio = 7
$CC3IR09
Code 39 Interdigit Ratio = 9
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$CC3IR06 
Code 39 Interdigit Ratio = 6
$CC3IR08 
Code 39 Interdigit Ratio = 8
$CC3IR0A 
Code 39 Interdigit Ratio = 10
Programming Reference Guide
Code 39