If I sound surprised, I am. It's just that I had wasted a few days on identical-looking modules from another supplier, which did not work; their trigger LED's shone at different brightnesses; they were permanently energised/on regardless of triggering, and I thought I was doing something stupid. The ICQUANZX modules, on the other hand, look better, they energize when triggered, and their trigger LEDs are all the same brightness - implying quality. Without changing my code, I wired all five modules up and they worked right away. What a relief!