Editing Electrical connector (section)

==Mechanical features==

===Pin sequence===
Some connectors are designed such that certain pins make contact before others when inserted, and break first on disconnection.<ref name="ieee" /> This is often used in [[#Power connectors|power connectors]] to protect equipment, e.g. connecting [[safety ground]] first. It is also employed for digital signals, as a method to sequence connections properly in [[hot swapping]].

===Keying===
{{multiple image
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 | header = Examples of keyed connectors
 | image1 = XLR pinouts.svg
 | caption1 = [[XLR connector]], showing the notch for alignment
 | image2 = SVideoConnector.jpg
 | caption2 = A 4-pin [[Mini-DIN]] [[S-Video]] cable, with notches and a rectangular alignment pin
}}
Many connectors are '''keyed''' with some mechanical component (sometimes called a ''keyway''), which prevents mating in an incorrect orientation.<ref name="nykcs-circular" /> This can be used to prevent mechanical damage to connectors, from being jammed in at the wrong angle or into the wrong connector, or to prevent incompatible or dangerous electrical connections, such as plugging an audio cable into a power outlet.<ref name="ieee" /> Keying also prevents otherwise symmetrical connectors from being connected in the wrong orientation or ''polarity''. Keying is particularly important for situations where there are many similar connectors, such as in signal electronics.<ref name="zvei" />{{rp|26}} For instance, [[XLR connector]]s have a notch to ensure proper orientation, while [[Mini-DIN]] plugs have a plastic projection that fits into a corresponding hole in the socket (they also have a notched metal skirt to provide secondary keying).<ref name="lsf">{{cite book |last1=Evans |first1=Bill |title=Live sound fundamentals |year=2011 |url=https://archive.org/details/livesoundfundame00evan |url-access=limited |publisher=Course Technology |isbn=978-1-4354-5494-1 |pages=[https://archive.org/details/livesoundfundame00evan/page/n36 24], 29}}</ref>

===Locking mechanisms===
Some connector housings are designed with locking mechanisms to prevent inadvertent disconnection or poor environmental sealing.<ref name="ieee" /> Locking mechanism designs include locking levers of various sorts, [[Jackscrews#In electronic connectors|jackscrew]]s, screw-in shells, [[push-pull connector]], and toggle or [[bayonet connector|bayonet]] systems.  Some connectors, particularly those with large numbers of contacts, require high forces to connect and disconnect.  Locking levers and jackscrews and screw-in shells for such connectors frequently serve both to retain the connector when connected and to provide the force needed for connection and disconnection.  Depending on application requirements, housings with locking mechanisms may be tested under various environmental simulations that include physical shock and vibration, water spray, dust, etc. to ensure the integrity of the electrical connection and housing seals.

===Backshells===
'''Backshells''' are a common accessory for industrial and high-reliability connectors, especially [[#Circular connectors|circular connectors]].<ref name="amphenol-backshells">{{cite web |url=https://docs-emea.rs-online.com/webdocs/1593/0900766b815933a9.pdf |title=Backshells by Amphenol Socapex |website=RS Components Ltd |publisher=Amphenol Socapex |date=2 November 2016 |access-date=26 June 2019}}</ref> Backshells typically protect the connector and/or cable from environmental or mechanical stress, or shield it from [[electromagnetic interference]].<ref name="cdm-backshells">{{cite web |url=https://cdmelectronics.com/wp-content/uploads/2014/05/How_To_Select_the_Proper_Backshell_31.pdf |title=How to Select the Proper Backshell |website=CDM Electronics |date=12 June 2012 |access-date=26 June 2019}}</ref> Many types of backshells are available for different purposes, including various sizes, shapes, materials, and levels of protection. Backshells usually lock onto the cable with a clamp or moulded boot, and may be threaded for attachment to a mating receptacle.<ref name="backshell-def">{{cite web |url=http://www.interfacebus.com/Glossary-of-Terms-Back-shell.html |title=Back Shell Definition |website=Electronic Engineering Dictionary Terms |date=17 March 2012 |last1=David |first1=Larry |access-date=30 June 2019}}</ref> Backshells for military and aerospace use are regulated by SAE AS85049 within the USA.<ref name="backshellworld">{{cite web |url=https://www.amphenol.co.uk/sites/default/files/file/How%20to%20select%20a%20backshell.pdf |title=How to select a backshell |publisher=BackShellWorld.com |website=Amphenol Corporation |date=6 September 2008 |access-date=26 June 2019 |archive-date=14 February 2019 |archive-url=https://web.archive.org/web/20190214185126/https://www.amphenol.co.uk/sites/default/files/file/How%20to%20select%20a%20backshell.pdf |url-status=dead }}</ref>

===Hyperboloid contacts===
To deliver ensured signal stability in extreme environments, traditional pin and socket design may become inadequate. Hyperboloid contacts are designed to withstand more extreme physical demands, such as vibration and shock.<ref name="nykcs-circular">{{cite web |url=https://www.nykcs.com/circular-connector-terminology-guide/ |title=Circular Connector Terminology Guide |website=NYK Component Solutions |last1=Worley |first1=Jon |date=31 July 2018 |access-date=2018-10-15}}</ref> They also require around 40% less insertion force<ref name="hyperboloid-connsupp" />{{snd}} as low as {{convert|0.3|N|oz-f|0}} per contact,<ref name="ieh-catalog">{{cite web |url=https://www.iehcorp.com/_uploads/pdf/catalogs/hgm.pdf |title=IEH Hyperboloid Connectors |website=IEH Corporation |date=October 2017 |access-date=27 June 2019}}</ref>{{snd}}which extends the lifespan, and in some cases offers an alternative to [[zero insertion force]] connectors.<ref name="ieh-hyperboloid">{{cite web |url=https://www.iehcorp.com/about/technology/ |website=IEH Corporation |title=Our Technology |access-date=26 June 2019}}</ref><ref name="hyperboloid-connsupp">{{cite web |url=https://www.connectorsupplier.com/modern-hyperboloid-contacts-for-circular-io-connectors/ |title=Modern Hyperboloid Contacts for Circular I/O Connectors |date=8 June 2015 |last1=Lascelles |first1=Robert |website=ConnectorSupplier.com |access-date=27 June 2019}}</ref>

In a connector with hyperboloid contacts, each female contact has several equally spaced longitudinal wires twisted into a hyperbolic shape. These wires are highly resilient to strain, but still somewhat elastic, hence they essentially function as linear springs.<ref name="hyperboloid-connector-tips">{{cite web |url=https://www.connectortips.com/would-you-trust-your-life-to-a-50-year-old-connector-design/ |title=Would you trust your life to a 50-year old connector design? |author=David Brearley |date=9 October 2015 |website=Connector Tips |access-date=27 June 2019}}</ref><ref name="hyperboloid-su-patent">{{cite patent |country=SU |number=1125684A1 |status=application |title=Hyperboloid-shaped socket for connection device |invent1=Pustynskij Nikolaj |pubdate=1983 |url=https://patents.google.com/patent/SU1125684A1}}.</ref> As the male pin is inserted, axial wires in the socket half are deflected, wrapping themselves around the pin to provide a number of contact points. The internal wires that form the hyperboloid structure are usually anchored at each end by bending the tip into a groove or notch in the housing.<ref name="hyperboloid-uk-patent">{{cite patent |country=GB |publication-number=2366097A |status=application |title=Hyperboloid electrical socket |pubdate=27 February 2002 |invent1=Donald Richard Lacoy |url=https://patents.google.com/patent/US6464546B2}}.</ref>

Whilst hyperboloid contacts may be the only option to make a reliable connection in some circumstances, they have the disadvantage of taking up greater volume in a connector, which can cause problems for high-density connectors.<ref name="hyperboloid-connsupp" /> They are also significantly more expensive than traditional pin and socket contacts, which has limited their uptake since their invention in the 1920s by Wilhelm Harold Frederick.<ref name="hyperboloid-us-patent">{{cite patent |country=US |publication-number=1833145A |status=patent |title=Connecter |pubdate=7 July 1925 |invent1=Wilhelm Harold Frederick |url=https://patents.google.com/patent/US1833145A}}.</ref> In the 1950s, Francois Bonhomme popularised hyperboloid contacts with his "Hypertac" connector, which was later acquired by [[Smiths Group]]. During the following decades, the connectors steadily gained popularity, and are still used for medical, industrial, military, aerospace, and rail applications (particularly trains in Europe).<ref name="hyperboloid-connector-tips" />

===Pogo pins===
{{main|Pogo pin}}
[[File:Pogo Pin Connectors.jpg|thumb|Pogo pin connectors]]
''Pogo pin'' or ''spring loaded'' connectors are commonly used in consumer and industrial products, where mechanical resilience and ease of use are priorities.<ref name="ccp">{{cite web |url=https://www.pccp.com.tw/product_detail.php?type_d=1&PNo=33 |website=C.C.P. Contact Probes Co. |title=Basic Pogo Pin Intro |access-date=3 July 2019 |archive-date=15 April 2019 |archive-url=https://web.archive.org/web/20190415022752/https://www.pccp.com.tw/product_detail.php?type_d=1&PNo=33 |url-status=dead }}</ref> The connector consists of a barrel, a spring, and a plunger. They are in applications such as the [[MagSafe (laptop power connector)|MagSafe]] connector where a quick disconnect is desired for safety. Because they rely on spring pressure, not friction, they can be more durable and less damaging than traditional pin and socket design, leading to their use in [[in-circuit test]]ing.<ref>{{cite web |url=http://www.qualmax.com/ |title=Welcome to Qualmax |website=Qualmax |access-date=3 July 2019}}</ref>

===Crown spring connectors===
[[File:Crown Spring Render.png|thumb|Typical crown spring plug and its female socket]]
Crown spring connectors are commonly used for higher current flows and industrial applications. They have a high number of contact points, which provides a more electrically reliable connection than traditional pin and socket connectors.<ref>{{cite book |url={{Google books |_ghEDwAAQBAJ |page=408 |plainurl=yes |onepage=yes}} |title=Electrical Contacts: Principles and Applications |edition=2nd |last=Slade |first=Paul G. |publisher=CRC Press |year=2014 |isbn=978-1-4398-8130-9 |page=408}}</ref>