Very helpful Dean, should be a sticky.

For those of us using the old fashioned parallel port on the PC with a breakout board (BOB) the number of ins and outs is quite restricted, though 4 combined limit/end-stop inputs, an E-Stop input and a spindle start output work well enough for a basic beginner machine using LinuxCNC or MACH3. However that setup is getting long in the tooth now and even a cheapskate like me wouldn't advocate using it for a new machine.

Kit