Relay protection testing device is an important testing tool for ensuring power system running safely and reliably. HDJB series relay protection tester is a new style microcomputer relay protection test instrument. It can work alone or join with other computer. There is high-performance industrial control computer, high-speed digital signal processer, 16-bit DAC module, new style module type high fidelity power amplifier, TFT true-color LCD displayer and embedded microcomputer keyboard. Strong operation functions, small size, high precision.