This post explains for the SCR.
The Part Number is C107.
The function of this semiconductor is Silicon Controlled Rectifier.
Manufacturer: Digitron Electronic
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C107 is a kind of SCR ( Silicon Controlled Rectifier). Flat Pack Design, Up to 600 Volts 4 Amperes (RMS).
A Silicon Controlled Rectifier (SCR) is a type of semiconductor device that is widely used as a switch or rectifier in power control and voltage regulation circuits. It is a three-layer, four-terminal device that can control the flow of current in either direction and provide full-wave rectification in power conversion applications.
The SCR can be triggered or turned on by a small trigger current or voltage applied to its gate terminal, and it remains in the conducting state as long as the anode-to-cathode voltage is positive and the gate trigger current is maintained. The SCR can be turned off by reducing the anode-to-cathode voltage to zero or by removing the gate trigger current.
SCRs are widely used in power control and regulation applications, such as lighting and heating control, motor control, battery chargers, and AC-to-DC power conversion, due to their high voltage and current handling capabilities, fast switching speeds, and high reliability.