Widely used; Simple and easy to understand; Easy to use; Standby current: 9 mA; Working current: 40 mA; Working voltage: DC 12 V (DC 10–15 V); Dimensions: 44 mm × 29 mm × 19 mm; Maximum load: 10 A / 250 VAC, 10 A / 125 VAC, 10 A / 30 VDC, 10 A / 28 VDC, 10 A / 12 VDC. The relay features NO (normally open) and NC (normally closed) terminals for flexible control configurations. 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 well-isolated DC power supply. Applications include: - Automatic water supply systems for residential water towers - Aquarium water change systems - Automatic water tower filling - Conductive liquid level control - Poultry and livestock automatic feeding and watering systems - Farm water supply automation - Solenoid valve, water pump, and motor control Terminal labels: HIGH: Upper limit probe input OUT: Output signal terminal 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 Working principle (automatic 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. - As water level drops, the pump remains off until the level falls below the LOW probe again.