Main Page | See live article | Alphabetical index In electronics, a jack is a socket. In some cases it is arbitrary which of a pair of mating connectors is the plug, and which the socket. See plug. The term jack occurs in several related terms: In the telephone jack of old-style manual telephone exchanges, which is the socket fitting the original 1/4" jack plug, also known as a phone jack. In the RJ in RJ11, RJ45 and similar which stands for registered jack, see RJ-XX. In the name RCA jack, also known as a phono jack or 1/4" phono jack. When used with a size, the term jack refers to the socket that matches the corresponding size of jack plug, as in 6.5mm jack, 6.3mm jack, 1/4" jack, 3.5mm jack, miniature jack, 2.5mm jack, subminiature jack, and similarly for non-standard sizes. A headphone jack or earphone jack is normally one of the three standard sizes of jack, but the term could refer to any socket used for this purpose. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.