The printed circuit boards are made of insulating material. They have pads, i.e. soldering pads and "paths", i.e. electrical connections. Special electronic components are installed on specially prepared copper coated surface or with the use of through-hole technology. Printed circuit boards are commonly referred to as PCB. If we have a laminate, acid for etching paths, a marker pen, sandpaper and a drill, we can prepare the plate even at home. On the PCB, passive (resistors, capacitors) and active (transistors) electronic elements are connected in such a way that the electrical current flows between them.