- replaced DIP header with 13-pin 0.1" vertical header. Added labels to
the pins.
- removed left over unused diode
- reversed default on / default off labels on shiftlock mode jumper
block.
- adjust RC constants to use simple, common values and reduce number of
different part values.
- Create add-on PCB to provide reset/shiftlock function for older 542 and SB2
keyboards.