Re: The big red button
9 pin sub-D connectors should be used ONLY for one thing: serial cables.
When I do designs, I spend an inordinate amount of time, trying to insure that all the connectors are different, and that if some have to be the same, disaster will not ensue if they are interchanged.
I also have a great reluctance to bring DC power out to connectors if it's not current limited in some way. I've seen too many sparks.