Ok well this Thread is in response to this post and request from a new builder in another thread.

Quote Originally Posted by joe.ninety View Post
Dean,

I've seen this said a lot but I think what a lot of your seasoned CNC guys forget is that beginners, myself included, have no idea how many IO's they are likely to need? Or really what they're even needed for? I'm kinda guessing homing/limit switches and the like but can't think of much else.
If you get the chance (and I know you said in another thread you were very busy at the moment) could you just do a post about IO's and what the main needs for them are. I think it would help a great deal of people, the OP included.

Cheers
I'll try my best and it will take a few post's to do it justice so bare with me.