This part is a kind of semiconductor called BCX42.

Function of this product has PNP Silicon AF an Swiching Transistors.

Manufacturers : Infineon Technologies AG

Image and pinout :

Some of the text within the PDF file :

BCX42, BSS63 PNP Silicon AF an Swiching Transistors
For general AF applications
High breakdown voltage
Low collector-emitter saturation voltage
Complementary types: BCX41, BSS64 (NPN) 3 2 1 VPS05161 Type BCX42 BSS63 Maximum Ratings Parameter Marking DKs BMs 1=B 1=B Pin Configuration 2=E 2=E 3=C 3=C Package SOT23 SOT23 Symbol VCEO VCBO VEBO BSS63 100 110 5 BCX42 125 125 5 Unit V Collector-emitter voltage Collector-base voltage Emitter-base voltage DC collector current Peak collector current Base current Peak base current Total power dissipation, TS = 79 °C Junction temperature Storage temperature IC ICM IB IBM Ptot Tj Tstg 800 1 100 200 330 150 -65 ... 150 mA A mA mW °C Thermal Resistance Junction - soldering point 1) RthJS
215 K/W 1For calculation of R thJA pl [ ... ]

BCX42 PDF Datasheet Download