The Model 422HESP is designed to help protect against lightning strikes, power surges, and other types of voltage disturbances. Five RS-422/485 signals on terminal blocks are supported with a clamping voltage of approximately 6.8 volts. The 422HESP 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 422HESP offers two terminal posts and two metal mounting brackets which provide a good ground connection for the user. The 442HESP 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.The Model 422HESP is designed to help protect against lightning strikes, power surges, and other types of voltage disturbances. Five RS-422/485 signals on terminal blocks are supported with a clamping voltage of approximately 6.8 volts. The 422HESP 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 422HESP offers two terminal posts and two metal mounting brackets which provide a good ground connection for the user. The 442HESP 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.