Hope i understood your questions correctly.
Please refer to the latest G540 manual .pdf at:
There is a really helpful diagram on the last page.
Inputs 1 through 4 are generally wired to NC (normally closed) switches,G540 Low voltage for E-stop and limits?
C (common) side of the switch wired to the respected input on the G540 terminal.
NC (normally closed side of the switch wired to the common system ground.
There is no other voltage applied to the switches.
The power supply for the output are generally used to drive external relays.(5v wall wart or 7805 circuit) for less contact arc?
The power supply for these outputs is determined by the requirement of the relays.
( each output is able to sink a maximum of 1A at 50VDC )
So if using relays with 5VDC coils (less than 1A coils) the 5v wall wart would work well.