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.

• The RJ in RJ11, RJ45 and similar, 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. For example:

• 6.5mm jack
• 1/4" jack
• 3.5mm miniature jack
• 2.5mm subminiature jack

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.

Female Jack Connectors are by some people also called "Jill Connectors". This is derived from the childrens poem about Jack and Jill. This term is formally used by the Sound and Lighting Team of the Outeniqua High School in George, South Africa.

See also

• Jack plug