This part is a kind of semiconductor called BTA41-600B.

Function of this product has 40A TRIACS.

Manufacturers : ST Microelectronics

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Some of the text within the PDF file :

® BTA40 and BTA/BTB41 Series 40A TRIACS STANDARD MAIN FEATURES: Symbol IT(RMS) V DRM/VRRM IGT (Q1) Value 40 600 and 800 50 Unit A V mA G G A2 A1 A1 A2 DESCRIPTION Available in high power packages, the BTA/ BTB40-41 series is suitable for general purpose AC power switching. They can be used as an ON/ OFF function in applications such as static relays, heating regulation, water heaters, induction motor starting circuits, welding equipment... or for phase control operation in high power motor speed controllers, soft start circuits... Thanks to their clip assembly technique, they provide a superior performance in surge current handling capabilities. By using an internal ceramic pad, the BTA series provides voltage insulated tab (rated at 2500 V RMS) complying with UL standards (File re [ ... ]

BTA41-600B PDF Datasheet Download