In basic diagrams, the standard symbols for the circuit components are arranged in correspondence with the operational principle of the device, as well as to facilitate the reading of the diagram. In design diagrams, all or some of the components are represented as equivalent circuits; in such diagrams, sources of electromotive force, current, resistance, inductance, capacitance, and so on are assumed to be components with lumped parameters.
The operation that results is a linear combination of incoming signals to generate the output signal. The sign appearing alongside each input to the summing point indicates the sign of that signal as it appears in the output.
Electric circuits are used to transmit power as in high-voltage power lines and transformers or in low-voltage distribution circuits in factories and homes; to convert energy from or to its electrical form as in motors, generators, microphones, loudspeakers, and lamps; to communicate information as in telephone, telegraph, radio, and television systems; to process and store data and make logical decisions as in computers; and to form systems for automatic control of equipment.
Circuit diagrams show connectors between components and the locations of connectors and lead-ins; such diagrams also illustrate methods of laying out, mounting, and fastening conductors, cables, and piping. Others show external connections to other articles; such diagrams are used for the installation and operation of complex units. Diagrams showing the principal parts of a complex and the interconnections between subassemblies when the complex is installed and operated are designed primarily to give a general representation of the complex. Layout diagrams show the relative spatial arrangement of components.