Most schematic symbols are accompanied by labels. This “labels” maybe a combination of the following; reference ID, part number and value.
Reference ID is an identifier, such as “R1”, “C4” or “Q4”. The letter represents the type of component. The commonly used letters are R for resistor, C for capacitor, L for inductor, D for diode, Q for transistor and IC for integrated circuit. If there are several components of the same type in a circuit, the numeral suffix (as an example R2) is added to identify the particular component.
