Tiny Telephone
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.
The phone connector was invented for use in telephone switchboards in the 19th century and is still widely used. In its original configuration, the outside diameter of the "sleeve" conductor is 1⁄4 inch (6.35 millimetres). The "mini" connector has a diameter of 3.5 mm (0.14 in) and the "sub-mini" connector has a diameter of 2.5 mm (0.098 in).
Specific models are termed stereo plug, mini-stereo, mini jack, headphone jack and microphone jack, or are referred to by size, i.e. 3.5mm or 6.35mm.
In the UK, the terms jack plug and jack socket are commonly used for the respective male and female phone connectors. In the US, a stationary (more fixed) electrical connector is called a "jack". The terms phone plug and phone jack are sometimes used to refer to different genders of phone connectors, but are also sometimes used colloquially to refer to RJ11 and older telephone plugs and the corresponding jacks that connect wired telephones to wall outlets.
Phone plugs and jacks are not to be confused with the similar terms phono plug and phono jack (or in the UK, phono socket) which refer to RCA connectors common in consumer hi-fi and audiovisual equipment. The 3.5 mm connector is, however, sometimes—but counter to the connector manufacturers' nomenclature—referred to as mini phono.
Modern phone connectors are available in three standard sizes. The original 1⁄4 in (6.35 mm) version dates from 1878, when it was used for manual telephone exchanges, making it the oldest electrical connector standard still in use.
...
Wikipedia