The 2N1878 from New Jersey Semiconductor is a Silicon Controlled Rectifier with Breakover Voltage 100 V, Breakover Current 15 A, Gate Trigger Voltage 0.44 to 0.60 V, Gate Trigger Current 5 to 20 uA, Temperature Operating Range -65 to 150 Degree C. Tags: Stud Mount. More details for 2N1878 can be seen below.