This part is a kind of semiconductor called 25TTS12.
Function of this product has PHASECONTROLSCRTO-220FULLPAK.
Manufacturers : InternationalRectifier
Image and pinout :
Some of the text within the PDF file :
Bulletin I2135 rev. D 03/99 SAFEIR Series 25TTS..FP PHASE CONTROL SCR TO-220 FULLPAK Description/Features The 25TTS..FP SAFE IR series of silicon controlled rectifiers are specifically designed for medium power switching and phase control applications. The glass passivation technology used has reliable operation up to 125° C junction temperature. Typical applications are in input rectification (soft start) and these products are designed to be used with International Rectifier input diodes, switches and output rectifiers which are available in identical package outlines. Fully isolated package (VINS = 2500 VRMS) UL E78996 approved VT ITSM < 1.25V @ 16A = 300A VRRM 800 to 1600V Output Current in Typical Applications Applications Capacitive input filterTA = 55°C,T J = 125°C, common h [ ... ]