The 51RIA40 from RIR Power Electronics is a Silicon Controlled Rectifier with Breakover Voltage 400 V, Breakover Current 1200 A, Gate Trigger Voltage 2.5 V, Gate Trigger Current 100 mA, Temperature Operating Range -40 to 125 Degree C. Tags: Stud Mount. More details for 51RIA40 can be seen below.