A: The Cannon Electric company originally developed the connector we now commonly refer to as an “XLR” connector. The connector was originally named the “Cannon X” connector. When the latch was added, the name was changed to the “Cannon XL.” Two versions were later made, one filled with resilient polychloroprene or rubber (XLR) and one filled with plastic (XLP). An XLD version featured a key/groove design that prevented connectors and cables from being accidentally interconnected — a plug with a key on it cannot be inserted into a jack without the corresponding groove.
Soon after the XLR was invented, various other companies, such as Switchcraft and Neutrik, began manufacturing compatible connectors. Though the 3-pin version is most familiar to musicians and audio engineers, XLRs have been made with as few as two pins and as many as seven pins.
ITT now owns the Cannon brand and manufactures a wide range of connectors under that name.