Sorry, I said "digital" to make it clear I wasn't sensing a variable analog signal. They are on/off 24VAC signals from some European machinery. There are not accessible relays, rather when the machine is powered up, it sends a 24VAC signal. I need to detect when this happens so the PLC can take some coordinating action. There are PLC's with input modules that will detect 24VAC and that seems the simplest method. But I'd prefer to use a Vision PLC if possible, however I didn't see a module that would do it. But it's a good suggestion to just have the AC switch a relay that has a DC voltage going through it.
Or I suppose I could use a cheap Click PLC and 24VAC module (they have one), and have it output a DC signal to the Vision. I appreciate the comments; this is only my 3rd project , so I'm far from experienced...