The SCT151B-650R from SMC Diode Solutions is a Silicon Controlled Rectifier with Breakover Voltage 650 V, Breakover Current 120 A, Gate Trigger Voltage 0.75 to 1.5 V, Gate Trigger Current 4 to 15 mA, Temperature Operating Range -40 to 125 Degree C. Tags: Through Hole. More details for SCT151B-650R can be seen below.