The BC547 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 2SK2850, 2SK-2850, K2850, 2850 Is a 6A 900V 125W N-Channel MOSFET Or Field Effect Transistor TO-3P Package 3 Pin Leads, Product Manufactured by Company Fuji Electric Corp.
The low level triggers the relay module's power indicator (green) and the 4-way relay status indicator (red). User-friendly interface design, all interfaces can be directly connected through the terminal leads. Four fixing bolt holes are provided.
The µPD4723 is a high-breakdown voltage silicon gate CMOS line driver/receiver based on the EIA/TIA-232-E standard. The internal DC/DC converter can switch between multiple voltages, allowing it to operate with a single +3.3 V or +5 V power supply.
The 2N7000, 2N-7000, 7000 MOSFET Transistor has a drain voltage of 60V, gate voltage of 40V and a drain current of 200mA in a TO-92 case. A MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor.