The HS4040NAQ3 from Littelfuse is a Silicon Controlled Rectifier with Breakover Voltage 400 V, Breakover Current 40 A, Gate Trigger Voltage 2.2 V, Gate Trigger Current 0.065 A, Temperature Operating Range -40 to 150 Degree C. Tags: Through Hole. More details for HS4040NAQ3 can be seen below.