XLR connector

The XLR connector is a style of electrical connector, primarily found on professional audio, video, and stage lighting equipment. The connectors are circular in design and have between 3 and 7 pins. They are most commonly associated with balanced audio interconnection, including AES3 digital audio, but are also used for lighting control, low-voltage power supplies, and other applications. XLR connectors are available from a number of manufacturers and are covered by an international standard for dimensions, IEC 61076-2-103. They are superficially similar to the older and smaller DIN connector range, but are not physically compatible with them.

A smaller version, the Mini XLR Connector, is used on smaller equipment.

The XLR connector was invented by James H. Cannon, founder of Cannon Electric in Los Angeles, California (now part of ITT Corporation), and for this reason it was sometimes colloquially known as a Cannon plug or Cannon connector and in Japan as Cannon jack, though this term has since fallen out of common usage in the industry. Originally manufactured as the Cannon X series, by 1950 a locking mechanism was added (Cannon XL) and by 1955 a version surrounding the female contacts with a synthetic rubber polychloroprene insulation using the part number prefix XLR. There was also an XLP series which used a hard plastic insulation, but was otherwise the same. ITT Cannon originally manufactured XLR connectors in two locations Kanagawa, Japan and Melbourne, Australia. The Australian operation was sold to Alcatel Components in 1992 and then acquired by Amphenol in 1998. ITT Cannon continues to manufacture XLR connectors in Japan.

The Switchcraft corporation later started manufacturing compatible connectors, followed by Neutrik. Neutrik made a number of improvements to the connector and its second-generation design (known as the X-series) had just four parts for the cable connector and eliminated the small screws used by both Cannon and Switchcraft, which were prone to working loose, falling out and becoming lost. These improvements have made Neutrik the most popular brand of XLR connector.

...
Wikipedia