This part is a kind of semiconductor called BTB04-600.

Function of this product has SENSITIVE GATE TRIACS.

Manufacturers : Unisonic Technologies

Image and pinout :

Some of the text within the PDF file :

UNISONIC TECHNOLOGIES CO., LTD BTB04 Preliminary SENSITIVE GATE TRIACS  DESCRIPTION The UTC BTB04 is a 4A triacs, it uses UTC’s advanced technology to provide customers with high commutation performances and voltage insulated tab, etc. The UTC BTB04 is suitable for inductive loads, general purpose AC switching and an ON/OFF function in applications such as induction motor starting circuits, for phase control operation in light dimmers and static relays, etc.  FEATURES * Low gate trigger current * Low holding current  SYMBOL MT2 TRIAC G MT1  ORDERING INFORMATION Ordering Number Lead Free Halogen Free BTB04L-x-x-TA3-T BTB04G-x-x-TA3-T Package TO-220 Pin Assignment 123 MT1 MT2 G Packing Tube  SENSITIVITY AND TYPE PART NUMBER S D T ◎: Available VOLTAGE 400 [ ... ]

BTB04-600 PDF Datasheet Download