The product is mainly used for lightning protection of industrial control signal lines and is widely used in industrial control systems. The SPD is connected in series in the signal loop to prevent surges from invading equipment along the signal line and causing damage to the equipment. Suitable for intrinsically safe signal transmission systems with line-to-ground isolation. It can be applied to 0(4)~20mA, 0~10V analog and switch (digital) signal protection, and is suitable for 2-wire, 3-wire and 4-wire thermal resistors, thermocouples, RS-232, RS- 485, MODBUS, PROFIBUSDP, CAN, pressure transmitter, valve positioner, transmitter, frequency converter, electrical converter, flow meter, solenoid valve and other field instruments and control systems such as PLC, DCS's AI, AO, DI, Surge protection for I/O interfaces such as DO. Widely used in petroleum, chemical industry, natural gas, environmental protection, new energy and other industries.