The UT-764i opto-isolated PCI converter card, compatible with RS-232C standard, is capable of converting single-ended PCI signals to RS-232 signals with a built-in opto-isolator, capable of providing isolation voltages up to 2500Vrms, with a fast transient voltage suppressor protector, which is designed to protect the RS-232 interface with today's advanced TVS (Transient Voltage Suppressor) transient voltage suppressor, under normal conditions, the TVS tube is a high resistance state, when the TVS tube is subjected to an instantaneous high-voltage shock at both ends, it can reduce the impedance at both ends at a high rate, absorbing a large current, so that the voltage at both ends is clamped at a predetermined value, protecting the circuit components behind it from damage due to transient High-voltage shock and damage.