The BF423, BF-423, 423 is a High Voltage PNP Bipolar Transistor is designed for general purpose amplifier applications. This device is housed in the TO-92 package.
The Type-C USB Charging Discharging Boost Module is a DC-5V 2A, This is a high precision DC5V 2A Charge Discharge Integrated Module Type-C Input compatible with 4.2v/4.35v Lithium Batteries.
The BC548 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin.