This post explains for the semiconductor T7812CT.
The Full Part Number is MCT7812CT.
The function of this semiconductor is Three-Terminal Positive 12V Voltage Regulator.
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These voltage regulators are monolithic integrated circuits designed as fixed-voltage regulators for a wide variety of applications including local, on-card regulation. These regulators employ internal current limiting, thermal shutdown, and safe-area compensation. With adequate heatsinking they can deliver output currents in excess of 1.0 A. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.
• Output Current in Excess of 1.0 A
• No External Components Required
• Internal Thermal Overload Protection
• Internal Short Circuit Current Limiting
• Output Transistor Safe-Area Compensation
• Output Voltage Offered with a 4% Tolerance
• Available in Surface Mount D2PAK and Standard 3-Lead Transistor Packages