View source for Electrical connector

{{Short description|Device used to join electrical conductors}}

[[File:ConnectorSymbols.svg|200px|thumb|Schematic symbols for male and female connectors {{crossreference|text=(see [[Gender of connectors and fasteners]])}}]]
[[File:Nikko TRM-800 Amp back.jpg|thumb|250px|This rear panel of an [[integrated amplifier]] features a variety of electrical connectors]]
[[File:ATX computer case - back - 2018-03-18.jpg|thumb|Connectors on the back of a 2018 computer]]

Components of an [[electrical circuit]] are '''electrically connected''' if an [[electric current]] can run between them through an [[electrical conductor]]. An '''electrical connector''' is an [[electromechanical]] device used to create an electrical connection between parts of an electrical circuit, or between different electrical circuits, thereby joining them into a larger circuit.<ref name="ieee">{{cite web |url=https://www.globalspec.com/learnmore/electrical_electronic_components/connectors/connectors_electrical |title=Electrical Connectors Information |publisher=IEEE GlobalSpec |website=Engineering360 |access-date=30 June 2019}}</ref>

The connection may be removable (as for portable equipment), require a tool for assembly and removal, or serve as a permanent electrical joint between two points.<ref name="RSM98">{{cite book |title=Electrical Connector Handbook: Theory and Applications |last1=Mroczkowski |first1=Robert S. |publisher=McGraw Hill |year=1998 |isbn=0-07-041401-7 |chapter=Ch 1 |url=https://books.google.com/books?id=XGkw8YR-uXsC}}</ref> An [[adapter]] can be used to join dissimilar connectors. Most electrical connectors have a [[Gender of connectors and fasteners|gender]]{{snd}}i.e. the male component, called a ''plug'', connects to the female component, or ''socket''.

Thousands of configurations of connectors are manufactured for [[Power cord|power]], [[data (computing)|data]], and [[audiovisual]] applications.<ref name="elliott">{{cite book |title=Electromechanical Devices & Components |last1=Elliott |first1=Brian S. |publisher=McGraw-Hill Professional |year=2007 |isbn=978-0-07-147752-9 |edition=2nd |chapter=Chapter 9: Connectors}}</ref> Electrical connectors can be divided into four basic categories, differentiated by their function:<ref name="sparkfun">{{cite web |url=https://learn.sparkfun.com/tutorials/connector-basics/all |title=Connector Basics |website=SparkFun |author1=SFUptownMaker |access-date=30 June 2019}}</ref>
* ''inline'' or ''cable'' connectors permanently attached to a cable, so it can be plugged into another [[terminal (electronics)|terminal]] (either a stationary instrument or another cable)<ref name="connector-def">{{cite web |url=http://www.interfacebus.com/Glossary-of-Terms_C5.html |at=Connector|title=Engineering Definitions – 'Com' to 'Con' |website=Electronic Engineering Dictionary Terms |date=17 March 2012 |last1=David |first1=Larry |access-date=30 June 2019}}</ref>
* ''Chassis'' or ''panel'' connectors permanently attached to a piece of equipment so users can connect a cable to a stationary device
* ''PCB mount'' connectors soldered to a [[printed circuit board]], providing a point for [[Electrical cable|cable]] or [[wire]] attachment.<ref name="taoe" />{{rp|56}} (e.g. [[pin header]]s, [[screw terminal]]s, [[board-to-board connector]]s)
* ''Splice'' or ''butt'' connectors (primarily [[insulation displacement connector]]s) that permanently join two lengths of wire or cable

In computing, electrical connectors are considered a physical interface and constitute part of the [[physical layer]] in the [[OSI model]] of networking.

==Physical construction==
In addition to the classes mentioned above, connectors are characterised by their [[pinout]], [[#Methods of connection|method of connection]], materials, size, [[contact resistance]], [[Insulator (electricity)|insulation]], mechanical durability, [[IP code|ingress protection]], [[Service life|lifetime]] (number of cycles), and ease of use.

It is usually desirable for a connector to be easy to identify visually, rapid to assemble, inexpensive, and require only simple tooling. In some cases an equipment manufacturer might choose a connector specifically because it is ''not'' compatible with those from other sources, allowing control of what may be connected. No single connector has all the ideal properties for every application; the proliferation of types is a result of the diverse yet specific requirements of manufacturers.<ref name="zvei">{{cite book |url=https://www.zvei.org/fileadmin/user_upload/Presse_und_Medien/Publikationen/2016/November/Connectors_Technologies-and-Trends_engl/2016-11_Imagebroschuere_Steckverbinder_engl.pdf |title=Connectors – Technologies and Trends |date=August 2016 |publisher=ZVEI – German Electrical and Electronic Manufacturers’ Association}}</ref>{{rp|6}}

===Materials===
Electrical connectors essentially consist of two classes of materials: conductors and insulators. Properties important to conductor materials are contact resistance, [[Electrical conductivity|conductivity]], [[mechanical strength]], [[formability]], and [[resilience (materials science)|resilience]].<ref name="molex">{{cite web |url=http://www.piclist.com/images/com/marvin3m/www/http/connect/index.htm |title=Molex Connectors Explained, as used in Pinball |date=4 March 2005 |website=Marvin's Marvelous Mechanical Museum |access-date=1 July 2019}}</ref> Insulators must have a high [[electrical resistance]], withstand high temperatures, and be easy to manufacture for a precise fit

[[Electrode]]s in connectors are usually made of [[copper alloy]]s, due to their good conductivity and [[malleability]].<ref name="zvei" />{{rp|15}} Alternatives include [[brass]], [[phosphor bronze]], and [[beryllium copper]]. The base electrode metal is often coated with another inert metal such as [[gold]], [[nickel]], or [[tin]].<ref name="molex" /> The use of a coating material with good conductivity, mechanical robustness and corrosion resistance helps to reduce the influence of passivating oxide layers and surface adsorbates, which limit metal-to-metal contact patches and contribute to contact resistance. For example, copper alloys have favorable mechanical properties for electrodes, but are hard to solder and prone to corrosion. Thus, copper pins are usually coated with gold to alleviate these pitfalls, especially for analog signals and high-reliability applications.<ref name="gold-tin">{{cite web |url=https://www.connector.com/gold-or-tin-versus-gold-and-tin/#ixzz4irNbDrRT3 |title=Gold or Tin versus Gold and Tin? |website=Molex |last1=Endres |first1=Herbert |date=19 December 2011 |access-date=1 July 2019}}</ref><ref name="golden-rules">{{cite web |author=AMP Incorporated |title=Golden Rules: Guidelines For The Use Of Gold On Connector Contacts |date=29 July 1996 |publisher=Tyco Electronic Corporation |url=https://www.te.com/documentation/whitepapers/pdf/aurulrep.pdf |archive-url=https://web.archive.org/web/20180329092427/https://www.te.com/documentation/whitepapers/pdf/aurulrep.pdf |archive-date=29 March 2018 |url-status=dead |access-date=1 July 2019 |quote=Gold is generally specified as a contact coating for low level signal voltage and current applications, and where high reliability is a major consideration}}</ref>

Contact ''carriers'' that hold the parts of a connector together are usually made of plastic, due to its insulating properties. ''Housings'' or ''[[#backshells|backshells]]'' can be made of molded plastic and metal.<ref name="zvei" />{{rp|15}} Connector bodies for high-temperature use, such as [[thermocouple]]s or associated with large [[incandescent lamp]]s, may be made of fired ceramic material.

===Failure modes===
{{see also|Failure mode}}
The majority of connector failures result in [[Intermittent fault|intermittent]] connections or open contacts:<ref name="navy">{{cite web |url=https://www.navsea.navy.mil/Portals/103/Documents/NSWC_Crane/SD-18/PDFs/Products/Connectors/ConnectorsFailure.pdf |title=Connectors: Failure Mechanisms and Anomalies |access-date=1 July 2019 |website=Naval Sea Systems Command}}</ref><ref>Normalized failure mode distributions were originally compiled from a combination of: MIL-HDBK-978, “NASA Parts Application Handbook”, 1991; MIL-HDBK-338, “Electronic Reliability Design Handbook”, 1994; “Reliability Toolkit: Commercial Practices Edition", Reliability Analysis Center (RAC), 1998; and “Failure Mode, Effects, and Criticality Analysis (FMECA)”, RAC, 1993.</ref>

{| class="wikitable"
|-
! Failure mode
! Relative probability
|-
| Open circuit || 61%
|-
| Poor contact || 23%
|-
| Short circuit || 16%
|}

Connectors are purely [[Passivity (engineering)|passive]] components{{snd}}that is, they do not enhance the function of a circuit{{snd}}so connectors should affect the function of a circuit as little as possible. Insecure mounting of connectors (primarily chassis-mounted) can contribute significantly to the risk of failure, especially when subjected to extreme shock or vibration.<ref name="navy" /> Other causes of failure are connectors inadequately rated for the applied current and voltage, connectors with inadequate ingress protection, and threaded [[#Backshells|backshells]] that are worn or damaged.

High temperatures can also cause failure in connectors, resulting in an "avalanche" of failures{{snd}}ambient temperature increases, leading to a decrease in insulation resistance and increase in conductor resistance; this increase generates more heat, and the cycle repeats.<ref name="navy" />

[[Fretting]] (so-called ''dynamic corrosion'') is a common [[failure mode]] in electrical connectors that have not been specifically designed to prevent it, especially in those that are frequently mated and de-mated.<ref>{{cite web |publisher=[[TE Connectivity]] |url=http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Robotics/ENG_CS_82012_Ribbon_Cable_Interconnect_Sol_0412.pdf |title=Ribbon Cable Interconnect Solutions |page=30 |date=April 2012 |access-date=1 July 2019 |quote=By its design the traditional failure mode in tin plated connections, fretting corrosion, is prevented}}.</ref> Surface [[corrosion]] is a risk for many metal parts in connectors, and can cause contacts to form a thin surface layer that increases resistance, thus contributing to heat buildup and intermittent connections.<ref name="reliability">{{cite web |url=http://ieee-holm.org/h2004/h2004antler.pdf |title=A Perspective on Connector Reliability |last1=Mroczkowski |first1=Dr. Robert S. |publisher=connNtext |website=IEEE |access-date=1 July 2019 |date=15 October 2004 |archive-date=25 October 2021 |archive-url=https://web.archive.org/web/20211025000712/https://ieee-holm.org/h2004/h2004antler.pdf |url-status=dead }}</ref> However, remating or reseating a connector can alleviate the issue of surface corrosion, since each cycle scrapes a microscopic layer off the surface of the contact(s), exposing a fresh, unoxidised surface.

===Circular connectors===
Many connectors used for industrial and high-reliability applications are circular in cross section, with a cylindrical housing and circular contact interface geometries. This is in contrast to the rectangular design of some connectors, e.g. [[USB hardware#Connectors|USB]] or [[#Blade connector|blade connectors]]. They are commonly used for easier engagement and disengagement, tight environmental sealing, and rugged mechanical performance.<ref name="glenair">{{cite web |url=https://cdn.glenair.com/interconnects/pdf/intro2.pdf |title=Essential Connector Terms and Definitions for Specifiers of Interconnect Wiring Systems |publisher=Glenair, Inc |date=2004 |access-date=2019-06-25}}</ref> They are widely used in military, aerospace, industrial machinery, and rail, where [[MIL-DTL-5015]] and [[MIL-DTL-38999]] are commonly specified. Fields such as [[sound engineering]] and [[radio communication]] also use circular connectors, such as [[XLR connector|XLR]] and [[BNC connector|BNC]]. [[AC power plugs and sockets|AC power plugs]] are also commonly circular, for example, [[Schuko]] plugs and [[IEC 60309]].

[[File:N2K-CABLING.jpg|thumb|right|[[NMEA 2000]] cabling using M12 connectors]]
The [[M12 connector]], specified in IEC 61076-2-101, is a circular electrical plug/receptacle pair with 12mm OD mating threads, used in [[NMEA 2000]], [[DeviceNet]], [[IO-Link]], some kinds of [[Industrial Ethernet]], etc.<ref>
[https://www.turck.us/static/media/downloads/WP_Industrial_Ethernet_Connectivity.pdf "Field Guide: Industrial Ethernet Connectivity"].
2017.
</ref><ref>
Dietmar Röring.
[https://www.mouser.com/pdfdocs/PhoenixContactM12_vs_RJ45_White_Paper.PDF "M12 versus RJ45 Ethernet connection systems"].
2014.
</ref>

A disadvantage of the circular design is its inefficient use of panel space when used in arrays, when compared to rectangular connectors.

Circular connectors commonly use [[#Backshells|backshells]], which provide physical and electromagnetic protection, whilst sometimes also providing a method for locking the connector into a receptacle.<ref name="amphenol-backshells" /> In some cases, this backshell provides a [[hermetic seal]], or some degree of [[IP code|ingress protection]], through the use of [[grommet]]s, [[O-ring]]s, or [[potting (electronics)|potting]].<ref name="glenair" />

===Hybrid connectors===
Hybrid connectors allow the intermixing of many connector types, usually by way of a housing with inserts.<ref>{{cite book |section-url=https://www.its.bldrdoc.gov/fs-1037/dir-018/_2625.htm |section=Hybrid connector |url=https://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm |title=Telecommunications: Glossary of Telecommunication Terms (FS1037C) |publisher=National Telecommunications and Information Administration |date=23 August 1996}}</ref> These housings may also allow intermixing of electrical and non-electrical interfaces, examples of the latter being pneumatic line connectors, and [[Fiber-optic connectors|optical fiber connectors]]. Because hybrid connectors are modular in nature, they tend to simplify assembly, repair, and future modifications. They also allow the creation of composite cable assemblies that can reduce equipment installation time by reducing the number of individual cable and connector assemblies.

==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
 | align = right
 | direction = vertical
 | width = 150
 | 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>

==Methods of connection==
{{multiple image
|align=right
|width=125
|title=Plug and socket connectors
|direction=vertical
|image1=Amphenol 16pin male front.jpg
|caption1=Male [[MIL-DTL-5015]] plug
|image2=SVGA port.jpg
|caption2=Female [[VGA connector]]
|image3=Serial port.jpg
|caption3=Male [[serial port]] connector
|image4=IBMtrconnector detail.jpg
|caption4=Mating surfaces of a [[hermaphroditic connector]]
}}
Whilst technically inaccurate, electrical connectors can be viewed as a type of adapter to convert between two connection methods, which are permanently connected at one end and (usually) detachable at the other end.<ref name="zvei" />{{rp|40}} By definition, each end of this "adapter" has a different connection method{{snd}}e.g. the solder tabs on a male [[phone connector (audio)|phone connector]], and the male phone connector itself.<ref name="elliott" /> In this example, the solder tabs connected to the cable represent the permanent connection, whilst the male connector portion interfaces with a female socket forming a detachable connection.

There are many ways of applying a connector to a cable or device. Some of these methods can be accomplished without specialized tools. Other methods, while requiring a special tool, can assemble connectors much faster and more reliably, and make repairs easier.

The number of times a connector can connect and disconnect with its counterpart while meeting all its specifications is termed as ''mating cycles'' and is an indirect measure of connector lifespan.  The material used for connector contact, plating type and thickness is a major factor that determines the mating cycles.<ref>{{Cite web|title=Learn More about Connector Mating Cycles|url=https://www.amphenol-icc.com/connect/learn-more-about-connector-mating-cycles.html|access-date=2021-08-23|website=www.amphenol-icc.com}}</ref>

==={{Anchor|plug|socket}}Plug and socket connectors===
{{see also|Gender of connectors and fasteners|Pinout}}
Plug and socket connectors are usually made up of a male '''plug''' (typically pin contacts) and a female '''socket''' (typically receptacle contacts). Often, but not always, sockets are permanently fixed to a device as in a chassis connector {{See above}}, and plugs are attached to a cable. 

Plugs generally have one or more pins or prongs that are inserted into openings in the mating socket. The connection between the mating metal parts must be sufficiently tight to make a good electrical connection and complete the circuit. An alternative type of plug and socket connection uses [[#Hyperboloid contacts|hyperboloid contacts]], which makes a more reliable electrical connection. When working with multi-pin connectors, it is helpful to have a [[pinout]] diagram to identify the wire or circuit node connected to each pin.

Some connector styles may combine pin and socket connection types in a single unit, referred to as a [[hermaphroditic connector]].<ref name="taoe">{{cite book |url=https://books.google.com/books?id=LAiWPwAACAAJ |title=The Art of Electronics |edition=2nd |last1=Horowitz |first1=Paul |last2=Hill |first2=Winfield |publisher=Cambridge University Press |year=1989 |isbn=0-521-37095-7}}</ref>{{rp|56}} These connectors includes mating with both male and female aspects, involving complementary paired identical parts each containing both protrusions and indentations. These mating surfaces are mounted into identical fittings that freely mate with any other, without regard for gender (provided that the size and type match).

Sometimes both ends of a cable are terminated with the same gender of connector, as in many [[Ethernet]] patch cables. In other applications the two ends are terminated differently, either with male and female of the same connector (as in an [[extension cord]]), or with incompatible connectors, which is sometimes called an ''[[Adapter (computing)|adapter]] cable''.

Plugs and sockets are widely used in various connector systems including blade connectors, [[breadboard]]s, [[XLR connector]]s, [[Automobile auxiliary power outlet|car power outlets]], [[banana connector]]s, and [[phone connector (audio)|phone connectors]].

====Jacks and plugs<span class="anchor" id="jack"></span>====
[[File:Jackplug.jpg|thumb|left|upright=0.55|Male [[phone connector (audio)|phone plug]]]]
A '''jack''' is a connector that installs on the surface of a bulkhead or enclosure, and mates with its reciprocal, the '''plug'''.<ref name="jack-plug">{{cite web |url=https://www.cosjwt.com/jack-plug-male-female-connectors/ |title=Jack/Plug – Jack, Plug, Male, Female Connectors |website=An Engineer's Review |date=15 July 2009 |access-date=1 July 2019 |last1=Huggins |first1=John S.}}</ref> According to the [[ASME|American Society of Mechanical Engineers]],<ref name="asme-ref">{{cite book | title = Reference Designations for Electrical and Electronics Parts and Equipment: ASME Y14.44-2008 : Section 2.1.5.3 (2) | publisher = ASME, Fairfield, NJ | year = 2008 | url = http://catalog.asme.org/Codes/PrintBook/Y1444_Reference_Designations.cfm | url-status = dead | archive-url = https://web.archive.org/web/20100313114131/http://catalog.asme.org/Codes/PrintBook/Y1444_Reference_Designations.cfm | archive-date = 2010-03-13 | quote = the stationary (more fixed) connector of a mating pair shall be designated J or X ... The movable (less fixed) connector of a mating pair shall be designated P | access-date = 2012-02-03 }}</ref> the stationary (more fixed) connector of a pair is classified as a ''jack'' (denoted J), usually attached to a piece of equipment as in a chassis-mount or panel-mount connector. The movable (less fixed) connector is classified as a ''plug'' (denoted P),<ref name="asme-ref" /> designed to attach to a wire, cable or removable electrical assembly.<ref name="IEEE and ANSI, New York, NY">{{cite book | title = Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters): IEEE-315-1975 (Reaffirmed 1993): Section 22 | publisher = IEEE and ANSI, New York, NY | year = 1993 | url = https://www.google.com/search?hl=en&q=ieee-315-1975}}</ref> This convention is currently defined in ASME Y14.44-2008, which supersedes [[IEEE 200-1975]], which in turn derives from the long-withdrawn MIL-STD-16 (from the 1950s), highlighting the heritage of this connector naming convention.<ref name="jack-plug" /> IEEE 315-1975 works alongside ASME Y14.44-2008 to define jacks and plugs.

The term ''jack'' occurs in several related terms:
* The '''[[registered jack]]''' or '''[[modular connector|modular jack]]''' in RJ11, RJ45 and other similar connectors used for [[telecommunications]] and [[computer network]]ing
* The '''telephone jack''' of manual [[telephone switchboard]]s, which is the socket fitting the original {{convert|1/4|in|mm|2}} [[telephone plug]]
* The {{convert|1/4|in|mm|2}} '''[[Phone connector (audio)|phone jack]]''' common to many electronic applications in various configurations, sometimes referred to as a ''headphone jack''
* The '''[[RCA connector|RCA jack]]''', also known as a ''phono jack'', common to consumer audiovisual electronics
* The '''[[EIAJ connector|EIAJ jack]]''' for consumer appliances requiring a power supply of less than 18.0&nbsp;volts

===Crimp-on connectors===
[[File:Crimping tool 04.jpg|thumb|A wire and connector being crimped together with a crimping tool]]
{{main|Crimp (electrical)}}
'''Crimped connectors''' are a type of solderless connection, using mechanical friction and uniform deformation to secure a connector to a pre-stripped wire (usually stranded).<ref name="ieee" /> Crimping is used in [[line splice|splice]] connectors, crimped multipin plugs and sockets, and crimped coaxial connectors. Crimping usually requires a specialised crimping tool, but the connectors are quick and easy to install and are a common alternative to solder connections or insulation displacement connectors. Effective crimp connections deform the metal of the connector past its [[Yield (engineering)|yield point]] so that the compressed wire causes [[tension (physics)|tension]] in the surrounding connector, and these forces counter each other to create a high degree of [[static friction]]. Due to the elastic element in crimped connections, they are highly resistant to [[vibration]] and [[thermal shock]].<ref>{{cite web |url=http://www.rfcoaxconnectors.com/technical-crimp-vs-solder.php |title=Crimp vs Solder: Pros and Cons |date=1 December 2004 |access-date=1 July 2019 |website=RF Connectors |archive-date=1 July 2019 |archive-url=https://web.archive.org/web/20190701075755/http://www.rfcoaxconnectors.com/technical-crimp-vs-solder.php |url-status=dead }}</ref>

Crimped contacts are permanent (i.e. the connectors and wire ends cannot be reused).<ref name="crimp-vs-solder">{{cite book |section-url=http://www.avielelectronics.com/Downloads/Catalog/Ref-Crimp-vs-Solder.pdf |title=Aviel Electronics Catalog |date=2013 |section=Crimp vs. Solder |access-date=1 July 2019}}</ref>

[[Crimp (electrical)|Crimped]] plug-and-socket connectors can be classified as ''rear release'' or ''front release''. This relates to the side of the connector where the pins are anchored:<ref name="nykcs-circular" />
* '''Front release contacts''' are released from the front (contact side) of the connector, and removed from the rear. The removal tool engages with the front portion of the contact and pushes it through to the back of the connector.
* '''Rear release contacts''' are released and removed from the rear (wire side) of the connector. The removal tool releases the contacts from the rear and pulls the contact out of the retainer.

===Soldered connectors===
{{see also|Soldering}}
Many plug and socket connectors are attached to a wire or cable by '''soldering''' conductors to electrodes on the back of the connector. Soldered joints in connectors are robust and reliable if executed correctly, but are usually slower to make than crimped connections.<ref name="ieee" /> When wires are to be soldered to the back of a connector, a [[#Backshell|backshell]] is often used to protect the connection and add strain relief. Metal ''solder buckets'' or ''solder cups'' are provided, which consist of a cylindrical cavity that an installer fills with solder before inserting the wire.<ref>{{cite web |url=https://www.rs-online.com/designspark/field-installable-the-secret-to-mastering-connectors |title=Field Installable: The secret to mastering connectors |website=Design Spark |publisher=RS Components |date=16 March 2017 |access-date=1 July 2019 |at=Solder connectors}}</ref>

When creating soldered connections, it is possible to melt the [[dielectric]] between pins or wires. This can cause problems because the thermal conductivity of metals causes heat to quickly distribute through the cable and connector, and when this heat melts plastic dielectric, it can cause [[short circuit]]s or "flared" (conical) insulation.<ref name="crimp-vs-solder" /> Solder joints are also more prone to mechanical failure than crimped joints when subjected to vibration and compression.<ref name="hpacademy">{{cite web |url=https://www.hpacademy.com/technical-articles/solder-vs-crimping/ |last1=Simon |first1=Andre |website=High Performance Academy |title=Solder Vs Crimping |access-date=1 July 2019}}</ref>

===Insulation-displacement connectors===
{{main|IDC (electrical connector)}}
Since stripping insulation from wires is time-consuming, many connectors intended for rapid assembly use '''insulation-displacement connectors''' which cut the insulation as the wire is inserted.<ref name="ieee" /> These generally take the form of a fork-shaped opening in the terminal, into which the insulated wire is pressed, which cut through the insulation to contact the conductor. To make these connections reliably on a production line, special tools accurately control the forces applied during assembly. On small scales, these tools tend to cost more than tools for crimped connections.

Insulation displacement connectors are usually used with small conductors for signal purposes and at low voltage. Power conductors carrying more than a few amperes are more reliably terminated with other means, though "hot tap" press-on connectors find some use in automotive applications for additions to existing wiring.

A common example is the multi-conductor flat ribbon cable used in computer disk drives; to terminate each of the many (approximately 40) wires individually would be slow and error-prone, but an insulation displacement connector can terminate all the wires in a single action. Another very common use is so-called [[punch-down block]]s used for terminating [[unshielded twisted pair]] wiring.

[[File:Bi-amp capable.jpg|thumb|upright=0.7|right|[[Binding post]]s on a [[Bi-amping and tri-amping|bi-amplified]] loudspeaker]]

===Binding posts===
{{main|Binding post}}
Binding posts are a single-wire connection method, where stripped wire is screwed or clamped to a metal electrode. Such connectors are frequently used in [[electronic test equipment]] and audio. Many binding posts also accept a [[banana connector|banana plug]].

===Screw terminals===
{{Main|Screw terminal block}}
Screw connections are frequently used for semi-permanent wiring and connections inside devices, due to their simple but reliable construction. The basic principle of all screw terminals involves the tip of a bolt clamping onto a stripped conductor. They can be used to join multiple conductors,<ref>{{cite web |url=http://updates.clipsal.com/ClipsalOnline/Files/Brochures/W0001868.pdf |title=Datasheet 563: Cable Connector |publisher=Clipsal |access-date=1 July 2019}}</ref> to connect wires to a [[printed circuit board]], or to terminate a cable into a plug or socket.<ref name="zvei" />{{rp|50}} The clamping screw may act in the longitudinal axis (parallel to the wire) or the transverse axis (perpendicular to the wire), or both. Some disadvantages are that connecting wires is more difficult than simply plugging in a cable, and screw terminals are generally not very well protected from contact with persons or foreign conducting materials.

[[Image:Terminal Blocks 01CJC.png|thumb|left|upright=0.9|Terminal blocks of various types]]
'''Terminal blocks''' (also called terminal ''boards'' or ''strips'') provide a convenient means of connecting [[individual]] electrical wires without a splice or physically joining the ends. Since terminal blocks are readily available for a wide range of wire sizes and terminal quantity, they are one of the most flexible types of electrical connector available. One type of terminal block accepts wires that are prepared only by stripping a short length of [[Electrical insulation|insulation]] from the end. Another type, often called ''barrier strips'', accepts wires that have ring or spade terminal ''lugs'' crimped onto the wires.

[[Printed circuit board]] (PCB) mounted '''screw terminals''' let individual wires connect to a PCB through leads soldered to the board.

===Ring and spade connectors===
[[Image:Ring wire end connector.jpg|thumb|upright=0.8|Ring style wire-end crimp connectors]]
The connectors in the top row of the image are known as '''ring terminals''' and '''spade terminals''' (sometimes called fork or split ring terminals). Electrical contact is made by the flat surface of the ring or spade, while mechanically they are attached by passing a screw or bolt through them. The spade terminal form factor facilitates connections since the screw or bolt can be left partially screwed in as the spade terminal is removed or attached. Their sizes can be determined by the [[American wire gauge|gauge]] of the conducting wire, and the interior and exterior diameters.

In the case of insulated crimp connectors, the crimped area lies under an insulating sleeve through which the pressing force acts. During crimping, the extended end of this insulating sleeve is simultaneously pressed around the insulated area of the cable, creating strain relief. The insulating sleeve of insulated connectors has a color that indicates the wire's [[IEC 60228|cross-section area]]. Colors are standardized according to DIN 46245:

* Red for cross-section areas from 0.5 to 1 mm²
* Blue for cross-section areas from 1.5 to 2.5 mm²
* Yellow for cross-section areas over 4 to 6 mm²

===Blade connectors===
{{see also|FASTON terminal}}
[[Image:Kabelschuh verschiedene commons.jpg|thumb|Blade connectors (lower half of photo). Ring and spade terminals (upper half). Bullet terminals, male and female (right-center, with blue wires)]]
A '''blade connector''' is a type of single wire, plug-and-socket connection device using a flat conductive blade (plug) that is inserted into a receptacle. Wires are typically attached to male or female blade connector terminals by either [[Crimp (electrical)|crimping]] or [[soldering]]. Insulated and uninsulated varieties are available. In some cases the blade is an integral manufactured part of a component (such as a switch or a speaker unit), and the reciprocal connector terminal is pushed onto the device's connector terminal.

===Other connection methods===
* [[Crocodile clip|Alligator and Crocodile clips]] – conductive clamps used for temporary connections, e.g. [[jumper cable]]s
* [[Board to board connector]]s – e.g. [[card-edge connector]]s or [[FPGA Mezzanine Card|FPGA mezzanine connectors]]
* [[Twist-on wire connector]]s (e.g. wire nuts) – used in [[low-voltage network|low-voltage]] power circuits for wires up to about 10&nbsp;AWG
* [[Wire wrap]]ping – used in older circuit boards

==See also==
{{div col}}
* [[Adapter]]
* [[Bent pin analysis]]
* [[Cable gland]]
* [[Electrical contact]]
* [[Electrical network]]
* [[Electrical termination]]
* [[Gender of connectors and fasteners]]
* [[InCa3D]]
* [[Lightbulb socket]]
* [[Line splice]]
* [[Pothead]] for a termination on a high voltage electric power cable
* [[Tee connector]]
* [[Tube socket]]
* [[Twist-on wire connector]]
{{div col end}}

===Connectors===
{{div col}}
* [[AC power plugs and sockets]]
* [[Audio and video interfaces and connectors]]
* [[Banana connector]]
* [[Battery holder]]
* [[Battery terminal]]
* [[Coaxial power connector]]
* [[Computer port (hardware)]]
* [[Crocodile clip]]
* [[DC connector]]
* [[DIN connector]]
* [[Dock connector]]
* [[D-subminiature|D-sub connectors]]
* [[Edge connector]]
* [[Elastomeric connector]]
* [[IEC 60320| IEC appliance couplers (IEC 60320)]]
* [[JST connector]]
* [[Mini-DIN connector]]
* [[Optical fiber connector]]
* [[Phone connector (audio)]]
* [[Pin header]]
* [[RCA connector]]
* [[RJ-XX]] connector
* [[Flexible electronics]]
{{div col end}}

== References ==
{{Reflist}}

;General
* Foreman, Chris, "Sound System Design", ''Handbook for Sound Engineers'', Third Edition, Glen M. Ballou, Ed., Elsevier Inc., 2002, pp.&nbsp;1171–72.

==External links==
{{Commons category-inline|Electrical connectors}}
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[[Category:Electrical connectors| ]]
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