Widely used; Simple and easy to understand; Easy to use; Standby current: 9 mA; Operating current: 40 mA; Operating voltage: DC 12 V (DC 10–15 V); Dimensions: 44 mm × 29 mm × 19 mm; Maximum load: 10 A / 250 V AC, 10 A / 125 V AC, 10 A / 30 V DC, 10 A / 28 V DC, 10 A / 12 V DC. The relay has NO (normally open) and NC (normally closed) terminals. For automatic water tower applications: - Connect the water pump to the COM and NC terminals for fill-on-low-level operation. - Connect the water pump to the COM and NO terminals for fill-on-low-level and stop-on-high-level operation. Note: Probe wires are not included. Standard insulated household wires may be used to construct probes. For safety, use a properly isolated DC power supply. Applications: Automatic water supply systems for residential water towers; Aquarium water change systems; Automatic water tower filling; Conductive liquid level control; Poultry and livestock feeding systems; Farm water supply systems; Solenoid valve, water pump, and motor control. Terminal labels: HIGH: Upper limit probe input OUT: Output signal LOW: Lower limit probe input DC+: Positive power supply input DC−: Negative power supply input NC: Relay normally closed contact COM: Relay common contact NO: Relay normally open contact Operation principle (water tower): - When water level is below the LOW probe, the pump starts. - When water level reaches or exceeds the HIGH probe, the pump stops. - When water level drops below the HIGH probe, the pump remains off until level falls below the LOW probe.