The BT151S-500R from WeEN Semiconductors is a Silicon Controlled Rectifier with Breakover Voltage 500 V, Breakover Current 120 A, Gate Trigger Voltage 0.25 to 1 V, Gate Trigger Current 0.015 A, Temperature Operating Range -40 to 150 Degree C. Tags: Surface Mount. More details for BT151S-500R can be seen below.