The MCD552-12io2 from Littelfuse is a Silicon Controlled Rectifier with Breakover Voltage 1200 V, Breakover Current 550 A, Gate Trigger Voltage 0.77 V, Gate Trigger Current 1300 A, Temperature Operating Range -40 to 125 Degree C. Tags: Surface Mount. More details for MCD552-12io2 can be seen below.