The Model 485HESP is designed to help protect against lightning strikes power surges and other types of voltage disturbances. Three RS-422/485 signals on terminal blocks are supported with a clamping voltage of approximately 6.8 volts. The 485HESP offers three stages of protection starting with a gas discharge tube followed by a series resistor and finally a Transient Voltage Suppresser (TVS). In order for a surge protector to work properly it is important to have a good connection to earth ground. The 485HESP offers two terminal posts and two metal mounting brackets which provide a good ground connection for the user. The 485HESP has been tested to two specifications at 6 kilovolts IEC 1000-4-5: 1995 "Surge Immunity Test" and IEEE C62.41-1991 "IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits". To ensure the best protection of your equipment some simple connection guidelines should be followed.