Relay can be used in various industries, such as:

1. Automobile industry: Relay is widely used in automobiles, mainly in the starting system, lighting system, fuel pump and other parts of the car. It is used to control the power supply and protect the car's electrical system.

2. Railway industry: Relay is also an important component of the railway signaling and control system, which is used to detect train positions, control train speeds and ensure train safety.

3. Power industry: In the power industry, relays are used to protect power systems from over current, over voltage and other abnormal conditions, and ensure the stable operation of power systems.

4. Telecommunications industry: Relays are widely used in the telecommunications industry, mainly in telephone exchanges, base stations and other equipment. They are used to control the connection and disconnection of telephone lines.

5. Industrial control industry: Relays are also widely used in industrial control systems, such as controlling machines, robots and other equipment, and ensuring that they operate normally.

In short, relays are widely used in various industries to achieve automatic control, protection and monitoring of equipment and systems.