The MSR interface: The MSR conforms to the USB HID standard for MSRs as described in the HID Usage Tables for POS, Ver 1.02, see http://www.usb.org/developers/hidpage.html#pos.
The Key Matrix: The Key Matrix report contains an overlay for the keyboard
Programmable Key Matrix
The keyboard matrix is completely programmable, translating between a key switch physical location and the key data reported to the host PC. Through this keyboard provision, you can switch the numeric keypad layout from the default calculator layout to a telephone layout by organizing the keyboard matrix to mimic either mode of operation.
Note: If you change the numeric keypad layout, you must also physically remove and swap the key caps on the first and third rows of the keypad. The key codes for the numeric keypad are identical to the IBM PS/2,
Double-high/Double-wide Keys
Several keys on the keyboard can accept optional keycaps that cover two keys to produce