The Siemens 3RG6142-3MM01 is a proximity switch — a PRXIMITY SW as the line calls it — built for detecting metal targets without contact in industrial automation. It's a straightforward inductive sensor, the kind you'd bolt onto a conveyor frame or machine slide to tell the PLC where things are.
What you're working with
The order code and category identify this as a proximity switch. Match barrel size, sensing distance, and wiring from the nameplate for field replacement.