The SerialComm ISO-485-P is a high-quality bi-directional industrial (wide temperature range) RS485 surge protector. It can protect any standard RS485 port from transients, peaks, and spikes caused by lightning and other power surges. The ISO-485-P protects the 2 lines: 485+ and 485-. The unit is passive, therefore, no external power or flow control is required. The ISO-485-P provides three stages of protection for maximum safety. The first stage is a gas discharge tube. The second stage is a series of protection resistors. The third stage is 600W Transient Voltage Suppressor (TVS). All three stages of protection are provided for each of the RS485 lines. When the ISO-485-P is placed close to the RS485 device it is protecting, it will suppress any voltage levels above 6.8 volts without affecting the normal operation of the data transmission. When installing the ISO-485-P is very important that the ground screw is connected to earth ground on both sides with a minimum of 12 AWG copper wire. The ISO-485-P has a 3-wire terminal block on one RS485 side and a 3-wire terminal block on the other RS485 side. This product is backed by our 30-day money back guarantee and 5-year replacement warranty. Three Stage Protection of both lines of the RS485 port, Operates from 300 to 1Mps baud Passive: no need for external power Heavy-duty steel case, Simple Plug-and-Play, Terminal connections for easy installation, Clamping Voltage at 6.8V 600W of surge protection from electrical surges and lightning strikes, Pre-tested 99.9% failure rate MEAN TIME BEFORE FAILURE: 309,122 Hours