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.
The DMG2302U-7 is 20V 4.2A 800 mW SOT23 Package. This N channel MOSFET transistor operates in enhancement mode. This MOSFET transistor has an operating temperature range of -55 °C to 150 °C.
This is a 2-Bit Bidirectional Voltage Level Translator I2C IIC Level Module CJMCU-0102 TXS0102.This two-bit non-inverting translator can be used to provide digital switching compatibility between mixed-voltage systems because it is a bidirectional voltage