Editing Electrical connector (section)

===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" />