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.
The field of electronic circuits is very broad and there are a very large number of other circuits besides those discussed above. For example, the differential is a key element in operational amplifier design and in biomedical data acquisition devices which must also be interfaced with specialized electronic sensors. Light-emitting and -detecting diodes allow for signals to be transmitted and received at optical frequencies. Liquid crystals are controlled by electronic circuits and are useful in digital watches, flat-panel color television displays, and electronic shutters.
The path taken by an electric current in flowing through a conductor through one complete run of a set of wires from a power source, such as a panelboard, to various electrical devices and back to the same power source. The wires used for various circuits are prescribed by codes, such as the National Electrical Code.
The active elements are the sources of electric energy for the circuit; they may be batteries, direct-current generators, or alternating-current generators. The passive elements are resistors, inductors, and capacitors. The electric circuit is described by a circuit diagram or map showing the active and passive elements and their connecting conducting paths.