A phone connector, also known as phone jack, audio jack, headphone jack or jack plug, is a common family of electrical connector typically used for analog signals, primarily audio. It is cylindrical in shape, typically with two, three, four and, recently, five contacts. Three-contact versions are known as TRS connectors, where T stands for"tip", R stands for "ring" and S stands for "sleeve". Similarly, two-, four- and five- contact versions are called TS, TRRS and TRRRS connectors respectively.