He touched a switch. A red LED on the board flickered. The computer saw it. The final section of the diagram showed a relay output.
Mark stared at the small green circuit board in his hand: the . To him, it looked like a city map with no street names—screw terminals, pin headers, and a mysterious parallel port. Mach3 Interface Board Wiring Diagram
He typed G91 X10 into the MDI line. Press Enter. He touched a switch