Transformers are normally pretty easy to identify by sight, and many have their specs printed on them. These components typically have plastic shells with their specification written on them. Powered relays are open while disconnected relays are closed. Inside the circle, one point goes directly to a bar, while the other leads branch off diagonally from the bar with one of them containing an arrow. Transistor diagrams are circles with three leads. Circuit boards often use Q to indicate transistor locations. You can identify them by their three terminals and their “D” shape. Transistors are a particular type of switch. In either case, PCBs use R to note resistors. Their schematic systems can also have this information printed in words as well. Larger resistors may have this information written on them as well. These small, horizontal cylinders often bear four or five colored stripes that help identify their resistance and tolerance. Resisters limit the flow of current through a circuit. They are also used in some electrical products, such as passive switch boxes. Printed circuit boards are used in all but the simplest electronic products. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it. PCB (printed circuit board) Parts and Components IdentificationĪ printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate.