GUS4 is a surge suppressor unit designed for use with contactors and reversing contactors in DC applications. It features an internal varistor and RC circuit combination that provides effective transient voltage suppression and arc quenching. The unit is rated for DC voltages in the 24–48V range and meets international safety standards with a rated insulation voltage (Ui) of AC 1000V and a rated impulse voltage (Uimp) of 8kV. With an IP20 degree of protection, GUS4 is suitable for industrial control systems where reliable surge suppression is essential to extend contactor life and prevent nuisance trips.