XLR / Pro Audio Cables & Adapters
The XLR connector is an electrical connector design. XLR plugs and sockets & used mostly in professional audio & video electronics cabling applications, for microphones & line level signals. Home audio & video electronics normally use RCA connectors for line level signals generated by a preamplifier. Phone plugs are also used for microphones in home and computer applications.
Originally the "Cannon X" series, subsequent versions added a Latch ("Cannon XL") and then a Rubber compound surrounding the contacts, which led to the abbreviation XLR. Many companies now make XLRs. The initials "XLR" have nothing to do with the pinout of the connector. XLR connectors can have other numbers of pins besides three.