I have two separate PLC. Both are having the I/O cards of 230 VAC. I have to give one signal from one PLC to other. I have taken a Digital output from PLC and given to Digital input card of other PLC. Please suggest what wiring I have to do? How the phase and neutral wiring will be done? Can I use the phase of first PLC card and the neutral of other PLC Card or I have to take the Phase and neutral of first PLC only?