The S4X8TS from Littelfuse is a Silicon Controlled Rectifier with Breakover Voltage 400 V, Breakover Current 0.8 A, Gate Trigger Voltage 1.7 V, Gate Trigger Current 0.0002 A, Temperature Operating Range -40 to 125 Degree C. Tags: Surface Mount. More details for S4X8TS can be seen below.