RS-485EVALBOARD4 is a compact evaluation board designed to assess circuit protection solutions for RS-485 serial ports. It integrates a Bourns TBU High-Speed Protector (HSP) dual-channel device, a Gas Discharge Tube (GDT) surge arrestor, and a Transient Voltage Suppressor (TVS) diode to meet industry standards for RS-485 port interfaces. The board measures 35 mm × 25 mm × 0.85 mm and is manufactured on FR-4 PCB with nickel-gold pad plating on both sides. It provides enhanced surge and transient protection performance while enabling compact PCB layouts compared to alternative protection solutions. The evaluation board supports multiple protection configurations and can accommodate AC power cross scenarios up to 230 VAC, making it suitable for harsh outdoor environments, long cable runs, and installation fault protection applications.