The Omron 61F-G2NL AC110/220 4KM is a High/Low level controller from the 61F series, designed for conductive liquid level detection in tanks, sumps, or reservoirs. It operates on a 110/220VAC supply and drives two SPDT relays (Form C) rated at 3A @ 200VAC, providing alarm-high contact output.
The standout spec here is the 4 km maximum distance between the controller and the sensor probe — that's the '4KM' in the order code. For a level controller, this means you can place the electronics in a central panel and run the probe out to a remote tank or well without worrying about signal drop. The sensitivity adjustment (0 to 0.7 kΩ) lets you tune the detection threshold for different liquid conductivities, from clean water to process fluids.
The two SPDT relays give you independent high- and low-level alarm outputs, or you can wire them for pump-up / pump-down control.