XLR connector
style of electrical connector found primarily in professional audio and lighting
XLR connector is a type of electronic connector that is mostly used with audio technology. Balanced and unbalanced circuits are possible with XLR when using monosignal per one XLR connection. Sound quality improves with a balanced circuit because noise is reduced, especially with microphones where the signal is often weak.
Wikimedia Commons has media related to XLR connectors.