The outside diameter of the 'sleeve' conductor is 6.35 millimetres ( 1⁄ 4 inch). Similarly, two-, four- and five- contact versions are called TS, TRRS and TRRRS connectors respectively. Ring contacts are typically the same diameter as the sleeve, the long shank. Three-contact versions are known as TRS connectors, where T stands for 'tip', R stands for 'ring' and S stands for 'sleeve'. In its original audio configuration, it typically has two, three, four or, occasionally, five contacts. The phone connector is cylindrical in shape, with a grooved tip to retain it. The phone connector was invented for use in telephone switchboards in the 19th century and is still widely used. The standard is that a plug (described as the male connector) will connect with a jack (described as female). Inserting the plug connects its tip to one part of that circuit instead.Ī phone connector, also known as phone jack, audio jack, headphone jack or jack plug, is a family of electrical connectors typically used for analog audio signals. When the plug is removed, those contacts close to connect a circuit such a connection is said to be 'normal'. Note the flat open contact spring parallel to and inside the tip contact spring. A pair of phone connectors: A plug (right) is inserted in a socket (jack, left).