This part is a kind of semiconductor called BTB12-800CW.

Function of this product has 12A TRIACS.

Manufacturers : ST Microelectronics

Image and pinout :

Some of the text within the PDF file :

BTA12, BTB12, T12xx 12 A Snubberless™, logic level and standard Triacs Datasheet - production data Features  Medium current Triac  Low thermal resistance with clip bonding  Low thermal resistance insulation ceramic for insulated BTA  High commutation (4Q) or very high commutation (3Q) capability  BTA series UL1557 certified (file ref: 81734)  Packages are RoHS (2002/95/EC) compliant Applications ON/OFF or phase angle function in applications such as static relays, light dimmers and appliance motors speed controllers. The Snubberless™ versions (BTA/BTB...W and T12 series) are especially recommended for use on inductive loads, because of their high commutation performance. The BTA series provide an insulated tab (rated at 2500 VRMS). Description Available either in [ ... ]

BTB04-600SAP PDF Datasheet Download