Editing Circuit diagram (section)

==Symbols==
{{Main|Electronic symbol}}
Circuit diagrams are pictures with symbols that have differed from country to country and have changed over time, but are now to a large extent internationally standardized. Simple components often had symbols intended to represent some feature of the physical construction of the device. For example, the symbol for a resistor dates back to the time when that component was made from a long piece of wire wrapped in such a manner as to not produce inductance, which would have made it a [[inductor|coil]]. These wirewound resistors are now used only in high-power applications, smaller resistors being cast from ''carbon composition'' (a mixture of [[carbon]] and [[Filler (materials)|filler]]) or fabricated as an insulating tube or chip coated with a metal film. The internationally standardized symbol for a resistor is therefore now simplified to an oblong, sometimes with the value in [[ohm]]s written inside, instead of the zig-zag symbol. A less common symbol is simply a series of peaks on one side of the line representing the conductor, rather than back-and-forth.

[[File:Wire Crossover Symbols for Circuit Diagrams.png|500px|thumb|'''Wire crossover symbols for circuit diagrams.''' The [[Computer-aided design|CAD]] symbol for insulated crossing wires is the same as the older, non-CAD symbol for non-insulated crossing wires. To avoid confusion, the wire "jump" (semi-circle) symbol for insulated wires in non-CAD schematics is recommended (as opposed to using the CAD-style symbol for no connection), so as to avoid confusion with the original, older style symbol, which means the exact opposite. The newer, recommended style for 4-way wire connections in both CAD and non-CAD schematics is to stagger the joining wires into T-junctions.<ref name = "electronicsclub.info">{{cite web|title=Circuit Symbols|url=http://electronicsclub.info/circuitsymbols.htm|website=electronicsclub.info|access-date=2 August 2014}}</ref>]]

The linkages between leads were once simple crossings of lines.  With the arrival of computerized drafting, the connection of two intersecting wires was shown by a crossing of wires with a "dot" or "blob" to indicate a connection. At the same time, the crossover was simplified to be the same crossing, but without a "dot". However, there was a danger of confusing the wires that were connected and not connected in this manner, if the dot was drawn too small or accidentally omitted (e.g. the "dot" could disappear after several passes through a copy machine).<ref>
"It is good practice to never use a + connection with a dot. Why? The dot can disappear when the schematic is copied for the 12th time." –
[http://www.siteswithstyle.com/VoltSecond/Schematic_notes/Schematic_reading_notes.html "Notes on Reading Schematics"] {{webarchive|url=https://web.archive.org/web/20111008031902/http://www.siteswithstyle.com/VoltSecond/Schematic_notes/Schematic_reading_notes.html |date=2011-10-08 }}
</ref>  As such, the modern practice for representing a 4-way wire connection is to draw a straight wire and then to draw the other wires staggered along it with "dots" as connections (see diagram), so as to form two separate T-junctions that brook no confusion and are clearly not a crossover.<ref>
"We recommend against using a 4-way connection point ... To avoid confusion, use only three-way connections." –
[http://www.engr.colostate.edu/~dga/mech307/project_report_samples/GF_Guidelines_8.pdf "Design News Gadget Freak Submission Guidelines"] {{webarchive|url=https://web.archive.org/web/20110929002946/http://www.engr.colostate.edu/~dga/mech307/project_report_samples/GF_Guidelines_8.pdf |date=2011-09-29 }}
</ref><ref>
"Wires connected at 'crossroads' should be staggered slightly to form two T-junctions" –
[http://www.kpsec.freeuk.com/symbol.htm "The Electronics Club: Circuit Symbols"]
</ref>

For crossing wires that are insulated from one another, a small semi-circle symbol is commonly used to show one wire "jumping over" the other wire<ref name = "electronicsclub.info" /><ref name="circuitstoday">{{cite web|title=Electronic Circuit Symbols |url=http://www.circuitstoday.com/electronic-circuit-symbols |website=www.circuitstoday.com |access-date=2 August 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141013185140/http://www.circuitstoday.com/electronic-circuit-symbols |archive-date=13 October 2014 }}</ref><ref>[http://www.electronicshub.org/symbols/ Electronics Circuit Symbols]</ref> (similar to how jumper wires are used).

A common, hybrid style of drawing combines the T-junction crossovers with "dot" connections and the wire "jump" semi-circle symbols for insulated crossings. In this manner, a "dot" that is too small to see or that has accidentally disappeared can still be clearly differentiated from a "jump".<ref name = "electronicsclub.info" /><ref name = "circuitstoday" />

On a circuit diagram, the [[electronic symbol|symbols]] for components are labelled with a descriptor or [[reference designator]] matching that on the list of parts. For example, C1 is the first [[capacitor]], L1 is the first [[inductor]], Q1 is the first [[transistor]], and R1 is the first [[resistor]]. Often the value or type designation of the component is given on the diagram beside the part, but detailed specifications would go on the parts list.

Detailed rules for reference designations are provided in the International standard [[IEC 61346]].