Changes
DualOS
,/* Construction */
Next you need to solder a flylead to pin 14 and pin 27. These leads need to go to a standard normally open switch mounted on the CPCs casing.
Closing the switch will set A14 to 0 zero and opening it sets A14 to one. This allows you to enable the upper or lower 16K of the EPROM and thus select which OS the CPC sees.