Q. What are RCA connectors called?

Answer

RCA is known as RCA phono connector or phono connector. The term "phono" in the term "phono connector" is an acronym of the word "phonograph," as this connector was initially designed to facilitate the connection of a phonograph disc to a radio receiver. A phono input is a series of input jacks on the back of a preamp, mixer, or amplifier—typically found on vintage radio sets—to which a phonograph or turntable can be connected. RCA first included this style of internal connector in their radio-phonograph floor consoles by no later than 1937.