The BT258-500R from WeEN Semiconductors is a Silicon Controlled Rectifier with Breakover Voltage 500 V, Breakover Current 75 A, Gate Trigger Voltage 0.1 to 1 V, Gate Trigger Current 0.2 A, Temperature Operating Range -40 to 150 Degree C. Tags: Through Hole. More details for BT258-500R can be seen below.