This one is a little variation of the one I got 3 years ago. This one has a separate terminal strip to supply interface Vcc, visible on the right near the bottom.

The interface can be totally isolated from the relay logic. The following 2 hookup diagrams illustrate the interface hookup. The interface only needs ground and an activation signal to activate a channel. The diode which will be turned on by the logic signal will optoisolate the input.