The BT139-800E is a two-way thyristor TRIACs from Kang Yang with a TO-220 package that is compliant with ROHS manufacturing protocols. It has a rated current of 10 mA, a power rating of 1 Watt, a gate triggering of 16A, and a latching current of 160A at 16.7 ms. This component is typically used as an on/off switch for AC electrical circuits.