What it is and what it does
The Omron E3JK-R2M1 is a retro-reflective photoelectric sensor using a visible red LED at 660 nm as its light source. The M.S.R. (Mutual Interference Rejection / Mirror Surface Rejection) function means it ignores reflections from shiny objects behind the reflector — useful on conveyors where glossy packaging or metal parts might otherwise cause false triggers. Sensing distance is 0 m to 2.5 m when paired with the E39-R1 reflector, and the standard sensing object is an opaque target 75 mm diameter minimum.
Output and wiring
Control output is a relay rated 0 to 3 A load current. That's a dry contact — universal voltage, no polarity, and it can switch a contactor coil, a solenoid valve, or an indicator lamp directly. No need for an interposing relay for most panel loads under 3 A.