If an input card has a negative common it requires a positive in - if a positive common a negative in. Outputs if the common 9load) is positive a negative out - if a negative (load) common a positive out. I do not take notice of sinking or sourcing anymore - manufacturers use the term differently. The explanation above is definitive - no ifs, buts or maybes. Have a look at the common on the card then whatever the manufacturer describes does not matter.