Editing Schematic (section)

==Electrical and electronic industry==
{{Main|Circuit diagram}}
[[File:Circuit diagram – pictorial and schematic.png|right|thumb|Comparison of pictorial and schematic styles of circuit diagrams]]
[[File:Joule_thief_schematic_de.svg|thumb|Example of a [[joule thief]] circuit driving an [[Light-emitting diode|LED]].]]

In electrical and electronic industry, a schematic diagram is often used to describe the design of equipment. Schematic diagrams are often used for the maintenance and repair of electronic and electromechanical systems.<ref name=FV75>Thomas E. French, Charles J. Vierck (1975). ''Engineering Drawing and Graphic Technology, Eleventh Edition''. McGraw Hill. {{ISBN|0-07-022157-X}}.  pp. 621–624.</ref> While schematics were traditionally drawn by hand, using standardized templates or pre-printed adhesive symbols, today [[electronic design automation]] software (EDA or "electrical CAD") is often used.

In electronic design automation, until the 1980s schematics were virtually the only formal representation for circuits. More recently, with the progress of computer technology, other representations were introduced and specialized [[computer language]]s were developed, since with the explosive growth of the complexity of electronic circuits, traditional schematics are becoming less practical. For example, [[hardware description language]]s are indispensable for modern [[digital circuit]] design.

Schematics for electronic circuits are prepared by designers using EDA ([[electronic design automation]]) tools called [[schematic capture]] tools or [[schematic entry]] tools. These tools go beyond simple drawing of devices and connections. Usually they are integrated into the whole design flow and linked to other EDA tools for verification and simulation of the circuit under design.

[[Programmable logic controller]]s (PLC) can be programmed using [[Ladder logic|ladder diagrams]].

In electric power systems design, a schematic drawing called a [[one-line diagram|''one-line'' ''diagram'']] is frequently used to represent [[Electrical substation|substations]], distribution systems or even whole electrical power grids. These diagrams simplify and compress the details that would be repeated on each phase of a [[three-phase]] system, showing only one element instead of three. Electrical diagrams for switchgear often have common device functions designate by [[ANSI Device Numbers|standard function numbers]]. Another type of diagram used for power systems is a ''three-line diagram''.

For analysis purposes of a power system, from the one-line diagram, if the system is balanced, an ''equivalent per-phase'' (or ''single-phase'') ''schematic diagram'' can be obtained. If all of the parameters are represented as impedances and voltage sources, the equivalent per-phase schematic diagram is called an ''impedance diagram''. If all of the parameters are represented as admittances and current sources, the equivalent per-phase schematic diagram is called an ''admittance diagram''.

If the power system is unbalanced, but it is [[Linear system|linear]] (or can be approximated by a linear system), then Fortescue's theorem ([[symmetrical components]]) can be applied. In this way, from the one-line diagram, three different per-phase schematic diagrams are obtained, known as ''sequence diagrams'': ''positive sequence diagram'', ''negative sequence diagram'', and ''zero sequence diagram''. Each of these diagrams can be represented as an impedance diagram or as an admittance diagram.