This is an application where we are using a fume extractor during laser coding. If the fume extractor cloggs up, it sends this 15v out. Not sure where it comes from, it's irrelevant I guess. We have to use this 15v on our laser circuit board but we wanna isolate it using an SSR. The SSR has two pins for the input A1 and A2, that's it. The output has 24v, ground and signal, so 3 pins, we know how to connect the output, no problem. The only issue is the output stays ON, even though the input changes to 0v, well we are assuming is 0v because we lose the 15v. This SSR is one of those green flat ones, where you snap onto those electrical rails inside an electrical panel.