The Siemens 3RG6233-3JS00 is a USONIC ultrasonic proximity switch in a compact M18 threaded-barrel housing. It operates on 20-30 VDC with a PNP output — a standard three-wire DC sensor configuration for industrial control panels.
The M18 barrel is the standard 18 mm cylindrical housing for proximity sensors — mounts in a standard M18 tapped hole or clamp bracket. The 20-30 VDC supply range covers nominal 24 VDC control systems with margin for brownout. A PNP (sourcing) output is common for PLC inputs in European-style panels; verify that the load side is configured for sourcing (positive-switching) logic.