The TA20121803DH from Powerex is a Silicon Controlled Rectifier with Breakover Voltage 1200 V, Breakover Current 40000 A, Gate Trigger Voltage 4.5 V, Gate Trigger Current 0.2 A, Temperature Operating Range -40 to 125 Degree C. Tags: Disc. More details for TA20121803DH can be seen below.