Surge protection, Triac thyristor, high current flow, Light control, Thermistors

 T435 Series 600 Vdrm 4 A Snubberless Triac AC Switch Surface Mount - TO-252

https://www.futureelectronics.com/p/electromechanical--circuit-protection--protection-thyristors/t435-600b-tr-stmicroelectronics-5752167