Electronic equipment is susceptible to transient disturbances from a variety of sources including ESD to an open connector or Interface, direct or nearby lightning strikes to cables and wires, and charged cables “hot plugged” into I/O ports. SP485-S is designed to protect Serial port from damage which may result from such transient events. The protection includes current limitation, voltage clamping, grounding the lightening and surge arresting using a mix of various protection devices to obtain a well balanced surge protector. This is a good alternative for long cables running through noisy areas or during lightening & noisy transients.