Hi

the 48 V relay you ordered - 48V Relay for Router Vac Control on 48V CNC Router System IE Gecko G540 | eBay will enable you to connect the relay coil ( the 2 small terminals)
to the +48V supply (for the G540) and the G540 output

http://www.homanndesigns.com/pdfs/EN010_V8.pdf


the G540 outputs can only connect the relay coil to ground when swiched on by the printer port pin going high

the output cannot supply a positive voltage to operate a relay as you may expect an output to do !


John