This part is a kind of semiconductor called C5478.

Function of this product has 2SC5478.

Manufacturers : Sanyo Semicon Device

Image and pinout :

Some of the text within the PDF file :

Features

1. High breakdown voltage
2. Small Cob
3. Wide ASO
4. High reliability ( Adoption of HVP process )

NPN Triple Diffused Planar Silicon Transistor

900V. 50mA switching applications.
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C5478 PDF Datasheet Download