This part is a kind of semiconductor called STR4A60.

Function of this product has Bi-Directional Triode Thyristor.

Manufacturers : SemiWell Semiconductor

Image and pinout :

Some of the text within the PDF file :

SemiWell Semiconductor Bi-Directional Triode Thyristor Symbol STR4A60 Features ◆ Repetitive Peak Off-State Voltage : 600V ◆ R.M.S On-State Current ( IT(RMS)= 4 A ) ◆ High Commutation dv/dt ○ 2.T2 ▼ ▲ ○ 3.Gate 1.T1 ○ General Description This device is new surface mounted package line up suitable for space limited application such as low power AC switching applications, such as fan speed, small light controllers and home appliance equipment. TO-126 3 2 1 Absolute Maximum Ratings Symbol VDRM IT(RMS) ITSM I2 t PGM PG(AV) IGM VGM TJ TSTG ( TJ = 25°C unless otherwise specified ) Condition Ratings 600 TC = 95 °C One Cycle, 50Hz/60Hz, Peak, Non-Repetitive 4.0 30/33 4.5 1.5 0.1 1 7.0 - 40 ~ 125 - 40 ~ 150 0.26 Parameter Repetitive Peak Off-State [ ... ]

STR4A60 PDF Datasheet Download