This part is a kind of semiconductor called STR4A60S.

Function of this product has Sensitive Gate Triacs.

Manufacturers : SemiWell Semiconductor

Image and pinout :

Some of the text within the PDF file :

SemiWell Semiconductor Sensitive Gate Triacs STR4A60S Symbol Features Repetitive Peak Off-State Voltage : 600V R.M.S On-State Current ( IT(RMS)= 4 A ) ◆ High Commutation dv/dt ◆ Sensitive Gate Triggering 4 Mode ◆ ◆ ○ 2.T2 ▼ ▲ ○ 3.Gate 1.T1 ○ General Description This device is sensitive gate triac suitable for direct coupling to TTL, HTL, CMOS and application such as various logic functions, 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 1.0 7. [ ... ]

STR4A60S PDF Datasheet Download