The Omron CRT1B-MD04JS-1 is a compact I/O slice for CJ, CS, and NJ series PLCs – two digital inputs and two solid-state outputs in a chassis-mount package with a rectangular backplane connector. It's the sort of module you'd find in a small control panel adding a couple of local I/O points without wasting DIN rail space.
Chassis mount with a rectangular connector — that means it bolts directly to the panel backplate, not onto DIN rail. IP20 rating says it's for a clean indoor cabinet, not for washdown zones or dusty enclosures. Operating temperature spans -10°C to 55°C, so it'll handle a warm cabinet but don't mount it next to a hot bearing housing or a steam line. Rated for use with CJ, CS, and NJ series controllers.