Phone connector (audio)

Invented in the late 19th century for telephone switchboards, the phone connector remains in use for interfacing wired audio equipment, such as headphones, speakers, microphones, mixing consoles, and electronic musical instruments (e.g. electric guitars, keyboards, and effects units).

Henry P. Clausen filed a patent[19] in 1901 for improved construction of the telephone switchboard-plug with today's 1⁄4 inch TS form still used on audio equipment.

[23] This roughly half-sized version of the original, popularized by the Sony EFM-117J radio (released in 1964),[24][25][failed verification] is still commonly used in portable applications and has a length of 15 millimetres (0.59 in).

The three-conductor version became very popular with its application on the Walkman in 1979, as unlike earlier transistor radios, these devices had no speaker of their own; the usual way to listen to them was to plug in headphones.

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 for a combination of stereo audio, a microphone, and controlling media playback, calls, volume and/or a virtual assistant on some laptop computers and most mobile phones,[27] and some handheld amateur radio transceivers from Yaesu.

[30] Professional audio and the telecommunication industry use a 0.173 in (4.4 mm) diameter plug, associated with trademarked names including Bantam, TT, Tini-Telephone, and Tini-Tel.

Though unable to handle as much power, and less reliable than a 6.35 mm (1⁄4 in) jack,[32] Bantam connectors are used for mixing console and outboard patchbays in recording studio and live sound applications, where large numbers of patch points are needed in a limited space.

[citation needed] A two-pin version, known to the telecom industry as a "310 connector", consists of two 1⁄4-inch phone plugs at a centre spacing of 5⁄8 inch (16 mm).

A similar type of 3.5 mm connector is often used in the armrests of older aircraft, as part of the on-board in-flight entertainment system.

A short-barrelled version of the phone plug was used for 20th-century high-impedance mono headphones, and in particular those used in World War II aircraft.

[40] Apple's September 2016 announcement of the iPhone 7 was initially mocked for removing the socket by other manufacturers like Samsung and Google who eventually followed suit.

[50] In the most common arrangement, consistent with the original intention of the design, the male plug is connected to a cable, and the female socket is mounted in a piece of equipment.

Support for input was dropped on various later models[53][54] The original application for the 6.35 mm (1⁄4 in) phone jack was in manual telephone exchanges.

Of these many varieties, only the two-conductor version with a rounded tip profile was compatible between different manufacturers, and this was the design that was at first adopted for use with microphones, electric guitars, headphones, loudspeakers, and other audio equipment.

This attempt has long been abandoned, and now the convention is that all plugs fit all sockets of the same size, regardless of whether they are balanced or unbalanced, mono or stereo.

For example, 3.5 mm TRRS sockets that accept TRRS headsets (stereo headphones with a mic) are often compatible with standard TRS stereo headphones, whereby the contact that expects a mic signal will instead simply become shorted to ground and thus will provide a zero signal.

[56] Because of a lack of standardization in the past regarding the dimensions (length) given to the ring conductor and the insulating portions on either side of it in 6.35 mm (1⁄4 in) phone connectors and the width of the conductors in different brands and generations of sockets, there are occasional issues with compatibility between differing brands of plug and socket.

These fall into three categories:[citation needed] Three- or four-conductor (TRS or TRRS) 2.5 mm and 3.5 mm sockets were common on older cell phones and smartphones respectively, providing mono (three-conductor) or stereo (four-conductor) sound and a microphone input, together with signaling (e.g., push a button to answer a call).

[60] The 4-pole 3.5 mm connector is defined by the Japanese standard JEITA/EIAJ RC-5325A, "4-Pole miniature concentric plugs and jacks", originally published in 1993.

Apple's iPod Shuffle 2G reuses its TRRS socket not just for audio but also for charging and syncing over USB when docked.

TRRRS connectors enable the following audio applications: active noise canceling, binaural recording and others, where dual analog microphone lines can be directly connected to a host device.

Another TRRRS standard for 4.4 mm connectors following JEITA RC-8141C was introduced in 2015 and is used for balanced audio connections, in particular for headphone cables.

This is accomplished by using one NC contact of a stereo jack to connect the tip and ring together to affect a bypass when no plug is inserted.

To eliminate the need for a separate power switch, a standard stereo jack is used on most battery-powered guitar effects pedals.

[88] When a phone connector is used to make a balanced audio connection, the two active conductors are used for differential versions of a monaural signal.

This causes bursts of hum, cracks and pops and may stress some outputs as they will be short circuited briefly, or longer if the plug is left half in.

[c] Older mixers and some outboard gear[d] have unbalanced insert points with ring send, tip return.

[e] In many implementations, the switch contact within the panel socket is used to close the circuit between send and return when the patch point has no plug inserted.

In some very compact equipment including modular synthesizers, 3.5 mm TS phone connectors are used for patch points.