A four-conductor version is often used in compact camcorders and portable media players, providing stereo sound and composite analog video.It is also used as a combined stereo headphone and microphone connector (i.e.The slightly different shape of bantam plugs is also less likely to cause shorting as they are plugged in.Less commonly used sizes, both diameters and lengths, are also available from some manufacturers, and are used when it is desired to restrict the availability of matching connectors, such as 0.210 inch inside diameter jacks for fire safety communication jacks in public buildings, the same size found in discontinued Bell & Howell 16 mm projector speaker jacks.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 It is today still used on mainstream musical equipment, especially on electric guitars.
Four- and five-conductor versions of the 3.5 mm plug and jack are used for certain applications.
The phone connector was invented for use in telephone switchboards in the 19th century and is still widely used.
The phone connector is cylindrical in shape, with a grooved tip to retain it.
These are mid-size TS or TRS phone plugs with a 4.4 mm (0.17 in) diameter shaft and a slightly different geometry.
In the telecommunications field, this is termed a "bantam" plug.