Solid state relay is a switching device that uses solid-state electronic devices (such as thyristors, transistors, etc.) to control current and voltage. Compared to traditional mechanical relays, solid-state relays have no moving parts, making them more durable and reliable. They are usually used in electrical control systems that require high speed, high frequency or large current, such as in industrial automation, mechanical equipment and power systems.

A time relay is an electrical control device used to open or close a circuit within a specific time interval. They are usually set up for automatic control systems and can implement switching functions or adjust the time delay of a circuit. Time relays are widely used in industrial fields, automation systems and equipment control.

A water level controller is a device used to monitor and control the level of liquids. It usually senses changes in water level through sensors, and then controls equipment such as valves or pumps based on preset parameters to maintain the water level within a set range. Water level controllers are widely used in water treatment, sewage treatment, water pump control systems, agricultural irrigation systems, and industrial production processes. It can improve water resource utilization efficiency, protect equipment and the environment, and also simplify the operation of water level adjustment.