{"history":[],"article":{"id":"e4341f0b-c5a8-4253-b783-169efc08f92d","title":"Phone connector (audio)","slug":"phone-connector-audio","content":":::summary\n:::\n\n# \nA **phone connector** is a family of [cylindrically](https://bliptext.com/articles/cylinder)-shaped [electrical connectors](https://bliptext.com/articles/electrical-connectors) primarily for [analog](https://bliptext.com/articles/analog-signal) [audio signals](https://bliptext.com/articles/audio-signal).\nInvented in the late 19th century for telephone switchboards, the phone connector remains in use for interfacing wired [audio equipment](https://bliptext.com/articles/audio-equipment), such as headphones, [speakers](https://bliptext.com/articles/loudspeaker), microphones, [mixing consoles](https://bliptext.com/articles/mixing-console), and [electronic musical instruments](https://bliptext.com/articles/electronic-musical-instruments) (e.g. [electric guitars](https://bliptext.com/articles/electric-guitars), [keyboards](https://bliptext.com/articles/electronic-keyboard), and [effects units](https://bliptext.com/articles/effects-units)).\nA male connector (a plug), is mated into a female connector (a socket), though [other terminology](https://bliptext.com/articles/) is used.\nPlugs have 2 to 5 [electrical contacts](https://bliptext.com/articles/electrical-contacts).\nThe **tip** contact is indented with a groove.\nThe **sleeve** contact is nearest the (conductive or insulated) [handle](https://bliptext.com/articles/handle).\nContacts are [insulated](https://bliptext.com/articles/insulation-electric) from each other by a band of non-conductive material.\nBetween the tip and sleeve are 0 to 3 **ring** contacts.\nSince phone connectors have many uses, it is common to simply name the connector according its number of rings:\nThe sleeve is usually a [common ground](https://bliptext.com/articles/ground-electricity) reference [voltage](https://bliptext.com/articles/voltage) or return [current](https://bliptext.com/articles/electric-current) for signals in the [tip and any rings](https://bliptext.com/articles/tip-and-ring).\nThus, the number of transmittable [signals](https://bliptext.com/articles/signal) is less than the number of contacts.\nThe outside diameter of the sleeve is 6.35 mm for full-sized connectors, 3.5 mm for \"[mini](https://bliptext.com/articles/)\" connectors, and only 2.5 mm for \"sub-[mini](https://bliptext.com/articles/)\" connectors.\nRings are typically the same diameter as the sleeve.\n# [Phone plug mated in a phone socket. The plug's grooved tip is held firmly by the socket's spring tip contact. When not mated, this spring instead connects to the flat switch contact for detecting a plug. | upload.wikimedia.org/wikipedia/commons/8/83/Mated-plug-socket-switched.jpg]\n# [TS and TRS plugs of different sizes | upload.wikimedia.org/wikipedia/commons/c/c1/Phone-connectors-labeled.jpg]\n\n# Other terms\nThe 1902 International Library of Technology simply uses jack for the female and plug for the male connector.\nThe 1989 Sound Reinforcement Handbook uses phone jack for the female and phone plug for the male connector.\nRobert McLeish, who worked at the [BBC](https://bliptext.com/articles/bbc), uses jack or jack socket for the female and jack plug for the male connector in his 2005 book Radio Production.\nThe [American Society of Mechanical Engineers](https://bliptext.com/articles/american-society-of-mechanical-engineers), as of 2007, says the more fixed [electrical connector](https://bliptext.com/articles/electrical-connector) is the jack, while the less fixed connector is the plug, without regard to the [gender](https://bliptext.com/articles/gender-of-connectors-and-fasteners) of the connector contacts.\nThe [Institute of Electrical and Electronics Engineers](https://bliptext.com/articles/institute-of-electrical-and-electronics-engineers) in 1975 also made a standard that was withdrawn in 1997.\nThe intended application for a phone connector has also resulted in names such as audio jack, headphone jack, stereo plug, microphone jack, aux input, etc. Among audio engineers, the connector may often simply be called a quarter-inch to distinguish it from [XLR](https://bliptext.com/articles/xlr-connector), another frequently-used audio connector.\nThese naming variations are also used for the 3.5 mm connectors, which have been called mini-phone, mini-stereo, mini jack, etc.\n[RCA connectors](https://bliptext.com/articles/rca-connector) are differently-shaped, but confusingly are similarly-named as phono plugs and phono jacks (or in the UK, phono sockets).\n3.5 mm connectors are sometimes—counter to the connector manufacturers' nomenclature —referred to as mini phonos.\nConfusion also arises because phone jack and phone plug may sometimes refer to the [RJ11](https://bliptext.com/articles/rj11) and various older [telephone sockets and plugs](https://bliptext.com/articles/telephone-jack-and-plug) that connect wired telephones to wall outlets.\n\n# Historical development\nThe original 1/4 in version descends from as early as 1877 in [Boston](https://bliptext.com/articles/boston) when the first telephone switchboard was installed or 1878, when an early switchboard was used for the first commercial [manual telephone exchange](https://bliptext.com/articles/telephone-switchboard) in [New Haven](https://bliptext.com/articles/new-haven) created by [George W. Coy](https://bliptext.com/articles/george-w-coy).\nCharles E. Scribner filed a patent in 1878 to facilitate switchboard operation using his spring-jack switch.\nIn it, a conductive [lever](https://bliptext.com/articles/lever) pushed by a [spring](https://bliptext.com/articles/spring-device) is normally connected to one contact.\nBut when a cable with a conductive plug is inserted into a hole and makes contact with that lever, the lever pivots and breaks its normal connection.\nThe receptacle was called a jack-knife because of its resemblance to a pocket [clasp-knife](https://bliptext.com/articles/clasp-knife).\nThis is said to be the origin of calling the receptacle a jack.\nScribner filed a patent in 1880 which removes the lever and resembles the modern connector and made improvements to switchboard design in subsequent patents filed in 1882.\nHenry P. Clausen filed a patent in 1901 for improved construction of the telephone switchboard-plug with today's 1/4 inch TS form still used on audio equipment.\n[Western Electric](https://bliptext.com/articles/western-electric) was the manufacturing arm of the [Bell System](https://bliptext.com/articles/bell-system), and thus originated or refined most of the engineering designs, including the telephone jacks and plugs which were later adopted by other industries, including the [US military](https://bliptext.com/articles/us-military).\nBy 1907, Western Electric had designed a number of models for different purposes, including:\nBy 1950, the two main plug designs were:\nSeveral modern designs have descended from those earlier versions:\n# [Mated connectors in Scribner's patent 489,570 filed on December 27, 1880 | upload.wikimedia.org/wikipedia/commons/d/dd/Scribner///Phone-Connector///Patent///489570.png]\n# [Henry P. Clausen's 1901 patent | upload.wikimedia.org/wikipedia/commons/a/a8/Clausen-telephone-switchboard-plug-patent.png]\n# [227x227px | upload.wikimedia.org/wikipedia/commons/7/7f/Oldphoneplugs.jpg]\n# [220x220px | upload.wikimedia.org/wikipedia/commons/e/ee/2-conductor///male///TS///connectors.jpg]\n\n## Military variants\nU.S. military versions of the Western Electric plugs were initially specified in Amendment No.1, MIL-P-642, and included:\n\n## Miniature size\nThe 3.5 mm or miniature size was originally designed in the 1950s as two-conductor connectors for earpieces on [transistor radios](https://bliptext.com/articles/transistor-radio), and remains a standard still used today.\nThis roughly half-sized version of the original, popularized by the Sony EFM-117J radio (released in 1964), is still commonly used in portable applications and has a length of 15 mm. The three-conductor version became very popular with its application on the [Walkman](https://bliptext.com/articles/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.\nThere is also an EIA standard for 0.141-inch miniature phone jacks.\nThe 2.5 mm or sub-miniature sizes were similarly popularized on small portable electronics.\nThey often appeared next to a 3.5 mm microphone jack for a remote control on-off switch on early portable tape recorders; the microphone provided with such machines had the on-off switch and used a two-pronged connector with both the 3.5 and 2.5 mm plugs.\nThey were also used for low-voltage DC power input from wall adapters.\nIn the latter role, they were soon replaced by coaxial [DC power connectors](https://bliptext.com/articles/dc-power-connector).\n2.5 mm phone jacks have also been used as headset jacks on mobile telephones (see ).\nThe 1/8 in and 1/10 in sizes, approximately 3.5 mm and 2.5 mm respectively in mm, though those dimensions are only approximations.\nAll sizes are now readily available in two-conductor (un[balanced](https://bliptext.com/articles/balanced-audio) mono) and three-conductor ([balanced](https://bliptext.com/articles/balanced-audio) mono or un[balanced](https://bliptext.com/articles/balanced-audio) stereo) versions.\nFour-conductor versions of the 3.5 mm plug and jack are used for certain applications.\nA four-conductor version is often used in compact [camcorders](https://bliptext.com/articles/camcorder) and portable media players, providing stereo sound and composite analog video.\nIt is also used for a combination of stereo audio, a microphone, and controlling media playback, calls, volume and/or a [virtual assistant](https://bliptext.com/articles/virtual-assistant) on some [laptop computers](https://bliptext.com/articles/laptop-computers) and most [mobile phones](https://bliptext.com/articles/), and some handheld [amateur radio](https://bliptext.com/articles/amateur-radio) transceivers from [Yaesu](https://bliptext.com/articles/yaesu-brand).\nSome headphone amplifiers have used it to connect balanced stereo headphones, which require two conductors per audio channel as the channels do not share a common ground.\n\n## Broadcast usage\nBy the 1940s, broadcast radio stations were using Western Electric Code No. 103 plugs and matching jacks for patching audio throughout studios.\nThis connector was used because of its use in [AT&T](https://bliptext.com/articles/at-t)'s Long Line circuits for the distribution of audio programs over the radio networks' leased telephone lines.\nBecause of the large amount of space these patch panels required, the industry began switching to 3-conductor plugs and jacks in the late 1940s, using the WE Type 291 plug with WE type 239 jacks.\nThe type 291 plug was used instead of the standard type 110 switchboard plug because the location of the large bulb shape on this TRS plug would have resulted in both audio signal connections being shorted together for a brief moment while the plug was being inserted and removed.\nThe Type 291 plug avoids this by having a shorter tip.\n\n## Patch bay connectors\n[Professional audio](https://bliptext.com/articles/professional-audio) and the telecommunication industry use a 0.173 in diameter plug, associated with trademarked names including Bantam, TT, Tini-Telephone, and Tini-Tel.\nThey are not compatible with standard EIA RS-453/IEC 60603-11 1/4-inch jacks.\nIn addition to a slightly smaller diameter, they have a slightly different geometry.\nThe three-conductor TRS versions are capable of handling balanced signals and are used in professional audio installations.\nThough unable to handle as much power, and less [reliable](https://bliptext.com/articles/reliability-engineering) than a 6.35 mm jack, Bantam connectors are used for [mixing console](https://bliptext.com/articles/mixing-console) and outboard [patchbays](https://bliptext.com/articles/patchbay) in recording studio and [live sound](https://bliptext.com/articles/live-sound) applications, where large numbers of patch points are needed in a limited space.\nThe slightly different shape of Bantam plugs is also less likely to cause shorting as they are plugged in.\n\n## Less common\nA 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 in.\nThe socket versions of these can be used with normal phone plugs provided the plug bodies are not too large, but the plug version will only mate with two sockets at 5/8 inches centre spacing, or with line sockets, again with sufficiently small bodies.\nThese connectors are still used today in telephone company central offices on \"DSX\" patch panels for [DS1 circuits](https://bliptext.com/articles/digital-signal-1).\nA 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](https://bliptext.com/articles/in-flight-entertainment) system.\nPlugging a stereo plug into one of the two mono jacks typically results in the audio coming into only one ear.\nAdapters are available.\nA 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](https://bliptext.com/articles/world-war-ii-aircraft).\nThese have become rare.\nIt is physically possible to use a normal plug in a short socket, but a short plug will neither lock into a normal socket nor complete the tip circuit.\nLess 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 in inside diameter jacks for fire safety communication in public buildings.\n# [A dual 310 patch cable, two-pin phone plug | upload.wikimedia.org/wikipedia/commons/6/68/Aadoublejackplug.jpg]\n\n## Decline\n[Digital audio](https://bliptext.com/articles/digital-audio) is now common and may be transmitted via [USB sound cards](https://bliptext.com/articles/usb-sound-card), USB headphones, [Bluetooth](https://bliptext.com/articles/bluetooth), [display connectors with integrated sound](https://bliptext.com/articles/audio-and-video-interfaces-and-connectors) (e.g. [DisplayPort](https://bliptext.com/articles/displayport) and [HDMI](https://bliptext.com/articles/hdmi)).\nDigital devices may also have internal speakers and mics.\nThus the phone connector is sometimes considered redundant and a waste of space, particularly on thinner [mobile devices](https://bliptext.com/articles/mobile-devices).\nAnd while low-profile [surface-mount](https://bliptext.com/articles/surface-mount) sockets [waterproofed up to 1 meter](https://bliptext.com/articles/ip67) exist, removing the socket entirely facilitates [waterproofing](https://bliptext.com/articles/waterproofing).\nChinese phone manufacturers were early in not using a phone socket: first with [Oppo](https://bliptext.com/articles/oppo)'s Finder in July 2012 (which came packaged with [micro-USB](https://bliptext.com/articles/micro-usb) headphones and supported [Bluetooth headphones](https://bliptext.com/articles/bluetooth-headphones)), followed by [Vivo](https://bliptext.com/articles/vivo-technology-company)'s X5Max in 2014 and [LeEco](https://bliptext.com/articles/leeco) in April 2016 and [Lenovo](https://bliptext.com/articles/lenovo)'s [Moto Z](https://bliptext.com/articles/moto-z) in September 2016.\n[Apple](https://bliptext.com/articles/apple-inc)'s September 2016 announcement of the [iPhone 7](https://bliptext.com/articles/iphone-7) was initially mocked for removing the socket by other manufacturers like [Samsung](https://bliptext.com/articles/samsung-electronics) and Google who eventually followed suit.\nThe socket is also not present in some tablets and thin laptops (e.g. [Lenovo](https://bliptext.com/articles/lenovo) Duet [Chromebook](https://bliptext.com/articles/chromebook) and [Asus](https://bliptext.com/articles/asus) [ZenBook](https://bliptext.com/articles/zenbook) 13 in 2020 ).\n\n# Aviation and US military connectors\nThe US military uses a variety of phone connectors including 9/32-inch (0.281-inch, 7.14 mm) and 1/4-inch (0.25 inch, 6.35 mm) diameter plugs.\nCommercial and [general aviation](https://bliptext.com/articles/general-aviation) (GA) civil aircraft headsets often use a pair of phone connectors.\nA standard 1/4-inch (6.3 mm) 2 or 3-conductor plug, type PJ-055, is used for headphones.\nFor the microphone, a smaller 3/16-inch (0.206 inch / 5.23 mm) diameter 3-conductor plug, type PJ-068, is used.\nMilitary aircraft and civil helicopters have another type termed the U-174/U (Nexus TP-101), also known as U-93A/U (Nexus TP-102) and Nexus TP-120.\nThese are also known as US NATO plugs.\nThese have a 0.281 in diameter shaft with four conductors, allowing two for the headphones, and two for the microphone.\nAlso used is the U-384/U (Nexus TP-105), which has the same diameter as the U-174/U but is slightly longer and has 5 conductors instead of 4.\nThere is a confusingly similar four-conductor British connector, Type 671 (10H/18575), with a slightly larger diameter of 7.57 mm used for headsets in many UK military aircraft and often referred to as a UK NATO or European NATO connector.\n# [PJ-055 (top) and PJ-068 (bottom) General Aviation Audio Phone Connectors | upload.wikimedia.org/wikipedia/commons/2/24/PJ-055///and///PJ-068///Connectors.png]\n\n# General use\nIn 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.\nA considerable variety of line plugs and panel sockets is available, including plugs suiting various cable sizes, right-angle plugs, and both plugs and sockets in a variety of price ranges and with current capacities up to 15 [amperes](https://bliptext.com/articles/ampere) for certain heavy-duty 1/4 in versions intended for [loudspeaker](https://bliptext.com/articles/loudspeaker) connections.\nCommon uses of phone plugs and their matching sockets include:\n# [A 3.5 mm phone connector | upload.wikimedia.org/wikipedia/commons/1/16/TRS///connector.JPG]\n# [A 3.5 mm 4-conductor TRRS phone connector | upload.wikimedia.org/wikipedia/commons/3/3b/3.5mm.jpg]\n# [A 3.5 mm 5-conductor TRRRS phone connector | upload.wikimedia.org/wikipedia/commons/1/11/Klinkenstecker///5-polig.jpg]\n\n# Computer sound\nAny number of 3.5 mm sockets for input and output may be found on [personal computers](https://bliptext.com/articles/personal-computers), either from [integrated sound hardware](https://bliptext.com/articles/sound-card) common on [motherboards](https://bliptext.com/articles/motherboards) or from insertable [sound cards](https://bliptext.com/articles/sound-cards).\nThe [1999 PC System Design Guide's color code](https://bliptext.com/articles/pc-system-design-guide) for 3.5 mm TRS sockets is common, which assigns pink for microphone, light blue for line in, and lime for line level.\n[AC'97](https://bliptext.com/articles/ac-97) and its 2004 successor [Intel High Definition Audio](https://bliptext.com/articles/intel-high-definition-audio) have been widely adopted specifications that, while not mandating physical sockets, do provide specifications for a [front panel connector](https://bliptext.com/articles/intel-high-definition-audio) with pin assignments for two ports with jack detection.\nFront panels commonly have a stereo output socket for headphones and (slightly less commonly) a stereo input socket for a mic.\nThe back panel may have additional sockets, most commonly for line out, mic, line in, and less commonly for multiple [surround sound](https://bliptext.com/articles/surround-sound) outs.\n[Laptops](https://bliptext.com/articles/laptops) and [tablets](https://bliptext.com/articles/tablet-computer) tend to have fewer sockets than [desktops](https://bliptext.com/articles/desktop-computer) due to size constraints.\n# [221x221px | upload.wikimedia.org/wikipedia/commons/b/bf/Desktop///sound///connectors.svg]\n# [This connector's color indicates it should plug into a computer's line audio out socket | upload.wikimedia.org/wikipedia/commons/8/8b/Audio-TRS-Mini-Plug.jpg]\n\n## Microphone power\nSome computers include a 3.5 mm TRS socket for mono microphone that delivers a 5 V [bias voltage](https://bliptext.com/articles/bias-voltage) on the ring to power an [electret microphone](https://bliptext.com/articles/electret-microphone)'s integrated [buffer amplifier](https://bliptext.com/articles/buffer-amplifier), though details depend on the manufacturer.\nThe [Apple](https://bliptext.com/articles/apple-inc) [PlainTalk](https://bliptext.com/articles/plaintalk) microphone socket is a historical variant that accepts either a 3.5 mm [line](https://bliptext.com/articles/line-level) input or an elongated 3.5 mm TRS plug whose tip carries the amplifier's power.\n\n## TRRS headset sockets\nSome newer computers, especially laptops, have 3.5 mm TRRS headset sockets, which are compatible with phone headsets and may be distinguished by a headset icon instead of the usual headphones or microphone icons.\nThese are particularly used for [voice over IP](https://bliptext.com/articles/voice-over-ip).\n\n## Surround sound\nSound cards that output [5.1 surround sound](https://bliptext.com/articles/5-1-surround-sound) have three sockets to accommodate six channels: front left and right; surround left and right; and center and subwoofer.\n6.1 and 7.1 channel sound cards from Creative Labs, however, use a single three-conductor socket (for the front speakers) and two four-conductor sockets.\nThis is to accommodate rear-center (6.1) or rear left and right (7.1) channels without the need for additional sockets on the sound card.\n\n## Combined TRS and TOSLINK\nSome portable computers have a combined 3.5 mm TRS/[TOSLINK](https://bliptext.com/articles/toslink) jack, supporting stereo audio output using either a TRS connector or [TOSLINK](https://bliptext.com/articles/toslink) (stereo or 5.1 [Dolby Digital](https://bliptext.com/articles/dolby-digital)/[DTS](https://bliptext.com/articles/dts-sound-system)) digital output using a suitable optical adapter.\nMost iMac computers have this digital/analog combo output feature as standard, with early MacBooks having two ports, one for analog/digital audio input and the other for output.\nSupport for input was dropped on various later models\n\n# Compatibility for different numbers of rings\nThe original application for the 6.35 mm (1/4 in) phone jack was in manual telephone exchanges.\nMany different configurations of these phone plugs were used, some accommodating five or more conductors, with several tip profiles.\nOf 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](https://bliptext.com/articles/microphone), electric guitars, [headphones](https://bliptext.com/articles/headphones), [loudspeakers](https://bliptext.com/articles/loudspeaker), and other [audio equipment](https://bliptext.com/articles/audio-equipment).\nWhen a three-conductor version of the 6.35 mm plug was introduced for use with stereo headphones, it was given a sharper tip profile to make it possible to manufacture jacks that would accept only stereo plugs, to avoid short-circuiting the right channel of the amplifier.\nThis 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.\nMost 6.35 mm plugs, mono or stereo, now have the profile of the original stereo plug, although a few rounded mono plugs are still produced.\nThe profiles of stereo miniature and sub-miniature plugs have always been identical to the mono plugs of the same size.\nThe results of this physical compatibility are:\nEquipment aware of this possible shorting allows, for instance:\nSome devices for an even higher number of rings might possibly be [backwards-compatible](https://bliptext.com/articles/backwards-compatible) with an opposite-gendered device with fewer rings, or may cause damage.\nFor 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.\nConversely, those TRRS headsets can plug into TRS sockets, in which case its speakers may still work even though its mic won't work (the mic's signal contact will be disconnected).\nBecause 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.\nThis can result in a contact in the socket bridging (shorting) the ring and sleeve contacts on a phone connector.\n\n# Video\nEquipment requiring video with stereo audio input or output sometimes uses 3.5 mm TRRS connectors.\nTwo incompatible variants exist, of 15 mm and 17 mm length, and using the wrong variant may either simply not work, or could cause physical damage.\nAttempting to fully insert the longer (17 mm) plug into a receptacle designed for the shorter (15 mm) plug may damage the receptacle, and may damage any electronics located immediately behind the receptacle.\nHowever, partially inserting the plug will work as the tip/ring/ring distances are the same for both variants.\nA shorter plug in a socket designed for the longer connector may not be retained firmly and may result in wrong signal routing or a short circuit inside the equipment (e.g. the plug tip may cause the contacts inside the receptacle – tip/ring 1, etc. – to short together).\nThe shorter 15 mm TRRS variant is more common and physically compatible with standard 3.5 mm TRS and TS connectors.\n# [Different length 3.5 mm TRRS connectors | upload.wikimedia.org/wikipedia/commons/e/ed/TRRS///3.5mm///-///2///length///variants.jpg]\n\n# Recording equipment\nMany small video cameras, laptops, recorders and other consumer devices use a 3.5 mm microphone connector for attaching a microphone to the system.\nThese fall into three categories:\n# [Stereo devices which use \"plug-in power\": the electret capsules are wired in this way. | upload.wikimedia.org/wikipedia/commons/5/5e/Jackplug-wiring.svg]\n\n# Mobile devices\nThree- or four-conductor (TRS or TRRS) 2.5 mm and 3.5 mm sockets were common on older cell phones and [smartphones](https://bliptext.com/articles/smartphone) 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).\nThese are used both for [handsfree](https://bliptext.com/articles/handsfree) [headsets](https://bliptext.com/articles/headset-audio) and for stereo headphones.\n3.5 mm TRRS (stereo-plus-mic) sockets became particularly common on [smartphones](https://bliptext.com/articles/smartphones), and have been used by Nokia and others since 2006, and as mentioned in the compatibility section, they are often compatible with standard 3.5 mm stereo headphones.\nMany computers, especially laptops, also include a TRRS headset socket compatible with the headsets intended for smartphones.\nThe four conductors of a TRRS connector are assigned to different purposes by different manufacturers.\nAny 3.5 mm plug can be plugged mechanically into any socket, but many combinations are electrically incompatible.\nFor example, plugging TRRS headphones into a TRS headset socket, a TRS headset into a TRRS socket, or plugging TRRS headphones from one manufacturer into a TRRS socket from another may not function correctly, or at all.\nMono audio will usually work, but stereo audio or the microphone may not work, or the pause/play controls may be inactive, as is common when trying to use headphones with controls for iPhones on an Android device, or vice versa.\n# [All iPhone models from the first generation to the 6S and SE (first generation) use a four-conductor (TRRS) phone connector (center) for a wired headset. | upload.wikimedia.org/wikipedia/commons/3/3b/iPod///and///iPhone///audio///plugs.JPG]\n\n## TRRS standards\nTwo different forms are frequently found.\nBoth place left audio on the tip and right audio on the first ring, same as stereo connectors.\nThey differ in the placement of the microphone and return contacts.\nThe [OMTP](https://bliptext.com/articles/omtp) standard places the ground return on the sleeve and the microphone on the second ring.\nIt has been accepted as a national Chinese standard YDT 1885–2009.\nIn the West, it is mostly used on older devices, such as older Nokia mobiles, older [Samsung](https://bliptext.com/articles/samsung) smartphones, and some [Sony Ericsson](https://bliptext.com/articles/sony-ericsson) phones.\nIt is widely used in products meant for the Chinese market.\nHeadsets using this wiring are sometimes indicated by black plastic separators between the rings.\nThe [CTIA](https://bliptext.com/articles/ctia-organization)/[AHJ](https://bliptext.com/articles/american-headset-jack) standard reverses these contacts, putting the microphone on the sleeve.\nIt is used by [Apple](https://bliptext.com/articles/apple-inc)'s [iPhone](https://bliptext.com/articles/iphone) line until the [6S](https://bliptext.com/articles/iphone-6s) and [SE (1st)](https://bliptext.com/articles/iphone-se-1st-generation).\nIn the West, these products made it the de facto TRRS standard.\nIt is now used by [HTC](https://bliptext.com/articles/htc) devices, recent [Samsung](https://bliptext.com/articles/samsung), [Nokia](https://bliptext.com/articles/nokia), and [Sony phones](https://bliptext.com/articles/sony-mobile), among others.\nIt has the disadvantage that the microphone gets shorted to ground if the device has a metal body and the sleeve has a flange, touching the body.\nHeadsets using this wiring are sometimes indicated by white plastic separators between the rings.\nIf a CTIA headset is connected to an OMTP device, the missing ground effectively connects the speakers in series, out-of-phase.\nThis removes the singer's voice on typical popular music recordings, which place the singers in the center.\nIf the main microphone button is held down, shorting across the microphone and restoring ground, the correct sound may be audible.\nThe 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.\n3-pole 3.5 mm TRS connectors are defined in JIS C 6560.\nSee also JIS C 5401 and IEC 60130-8.\n[Apple](https://bliptext.com/articles/apple-inc)'s [iPod Shuffle 2G](https://bliptext.com/articles/ipod-shuffle) reuses its TRRS socket not just for audio but also for charging and syncing over [USB](https://bliptext.com/articles/usb) when docked.\n\n### Interoperability\nThe USB Type-C Cable and Connector Specification specifies a mapping from a [USB-C](https://bliptext.com/articles/usb-c) jack to a 4-pole TRRS jack, for the use of headsets, and supports both CTIA and OMTP (YD/T 1885–2009) modes.\nSome devices transparently handle many jack standards, and there are hardware implementations of this available as components.\nThis is accomplished in some cases by applying a voltage to the sleeve and second ring to detect the wiring.\nThe last two conductors may then be switched to allow a device made to one standard to be used with a headset made to the other.\n\n## TRRRS standards\nA TRRRS standard for 3.5 mm connectors was developed by ITU-T.\nThe standard, called P.382 (formerly P.MMIC), outlines technical requirements and test methods for a 5-conductor socket and plug configuration.\nCompared to the TRRS standard, TRRRS provides one extra conductor that can be used for connecting a second microphone or providing power to or from the audio accessory.\nP.382 requires compliant sockets and plugs to be backward compatible with legacy TRRS and TRS connectors.\nTherefore, P.382-compliant TRRRS connectors should allow for seamless integration when used on new products.\nTRRRS 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.\nIt was commonly found on [Sony](https://bliptext.com/articles/sony) phones starting with the [Xperia Z1](https://bliptext.com/articles/xperia-z1)-[XZ1](https://bliptext.com/articles/sony-xperia-xz1) and [Xperia 1 II](https://bliptext.com/articles/xperia-1-ii).\nAnother TRRRS standard for 4.4 mm connectors following JEITA RC-8141C was introduced in 2015 and is used for [balanced audio](https://bliptext.com/articles/balanced-audio) connections, in particular for [headphone](https://bliptext.com/articles/headphone) cables.\nThis connector is often called a **Pentaconn** connector following the brand name of Nippon DICS (NDICS).\nIt is used by some Sony products like the [M1Z](https://bliptext.com/articles/m1z) Walkman of their Signature series and by some [Sennheiser](https://bliptext.com/articles/sennheiser) products like the [HD 820](https://bliptext.com/articles/hd-820) headphone or the HDV 820 DAC headphone amplifier.\n\n# Switch contacts\nPanel-mounted jacks may include switch contacts.\nMost commonly, a mono jack is provided with one normally closed (NC) contact, which is connected to the tip (live) connection when no plug is in the socket, and disconnected when a plug is inserted.\nStereo sockets commonly provide two such NC contacts, one for the tip (left channel) and one for the ring or collar (right channel).\nSome jacks also have such a connection on the sleeve.\nAs this contact is usually ground, it is not much use for signal switching but could be used to indicate to electronic circuitry that the jack is in use.\nLess commonly, jacks may feature normally open (NO) or change-over contacts or the switch contacts may be isolated from the connector signals.\nThe original purpose of these contacts was for switching in telephone exchanges, for which there were many patterns.\nTwo sets of change-over contacts, isolated from the connector contacts, were common.\nThe more recent pattern of one NC contact for each signal path, internally attached to the connector contact, stems from their use as headphone jacks.\nIn many amplifiers and equipment containing them, such as electronic organs, a headphone jack is provided that disconnects the loudspeakers when in use.\nThis is done by means of these switch contacts.\nIn other equipment, a dummy load is provided when the headphones are not connected.\nThis is also easily provided by means of these NC contacts.\nOther uses for these contacts have been found.\nOne is to interrupt a signal path in a mixing console to [insert](https://bliptext.com/articles/insert-effects-processing) an effects processor.\nThis 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.\nA similar arrangement is used in patch panels for normalization (see ).\nWhere a 3.5 mm or 2.5 mm jack is used as a DC power inlet connector, a switch contact may be used to disconnect an internal battery whenever an external power supply is connected, to prevent incorrect recharging of the battery.\nTo eliminate the need for a separate power switch, a standard stereo jack is used on most battery-powered guitar [effects pedals](https://bliptext.com/articles/effects-pedal).\nThe internal battery has its negative terminal wired to the sleeve contact of the jack.\nWhen the user plugs in a two-conductor (mono) plug, the resulting short circuit between the sleeve and ring connects an internal battery to the unit's circuitry, ensuring that it powers up or down automatically whenever a signal lead is inserted or removed.\n# [Miniature phone plugs and jacks. All are 3.5 mm except the gold-plated plug, which is 2.5 mm. One of the 3.5 mm jacks is two-conductor and the others are three conductor. In this collection the tan-colored jacks have normally-closed switches. | upload.wikimedia.org/wikipedia/commons/1/1b/Small///jack///plugs.jpg]\n\n# Design\nThe connector assembly is usually made by one or more hollow and one solid pin.\nThe jack is then assembled with pins separated by an [insulating](https://bliptext.com/articles/insulator-electricity) material.\nConnectors that are tarnished, or that were not manufactured within tight tolerances, are prone to cause poor connections.\nDepending upon the surface material of the connectors, tarnished ones can be cleaned with a burnishing agent (for solid brass contacts typical) or contact cleaner (for plated contacts).\n# [Examples of jack configurations, oriented so the plug enters from the right. The most common circuit configurations are the simple mono and stereo jacks (A and B); however, there are a great number of variants manufactured. \n

A two-conductor TS phone connector. The connection to the sleeve is the rectangle towards the right, and the connection to the tip is the line with the notch. Wiring connections are illustrated as white circles.
A three-conductor TRS phone connector. The upper connector is the tip, as it is farther away from the sleeve. The sleeve is shown connected directly to the chassis, a typical configuration for a balanced connection. Some jacks use plastic, to isolate the sleeve from the chassis, and provide a separate sleeve connection point, as in A.
This three-conductor jack has two isolated SPDT switches activated by a plug going into the jack, which disconnects one throw and connects the other. The white arrowheads indicate a mechanical connection, while the black arrowheads indicate an electrical connection. This configuration is useful for a device that turns on when a plug is inserted, and off otherwise, with the power routed through the switches.
This three-conductor jack has two normally closed switches connected to the contacts themselves. This is useful for patch panel normalization. Another common use is as stereo headphone jack that shuts off the default output (speakers) when the connector is plugged in.

| upload.wikimedia.org/wikipedia/commons/7/77/Phone///Jack///Symbols.svg]\n# [

Sleeve: Usually ground
Ring: Right-hand channel for stereo signals, negative polarity for balanced mono signals, power supply for power-using mono signal sources
Tip: Left-hand channel for stereo signals, positive polarity for balanced mono signals, signal line for unbalanced mono signals
Insulating rings

| upload.wikimedia.org/wikipedia/commons/9/93/Jack///plug.png]\n\n# Audio signals\n\n## Balanced audio\nWhen a phone connector is used to make a [balanced audio](https://bliptext.com/articles/balanced-audio) connection, the two active conductors are used for [differential](https://bliptext.com/articles/differential-signaling) versions of a monaural signal.\nThe ring, used for the right channel in stereo systems, is used instead for the inverting input.\n\n### Advantages\nWhere space is a premium, TRS connectors offer a more compact alternative to [XLR connectors](https://bliptext.com/articles/xlr-connector), and so are common in small audio [mixing desks](https://bliptext.com/articles/mixing-desk).\nAnother advantage offered by TRS connectors used for balanced microphone inputs is that a standard unbalanced signal lead using a TS phone jack can simply be plugged into such an input.\nThe inverting input on the ring contact gets correctly grounded when it makes contact with the plug body.\n# [The Sony Walkman NW-ZX300 has a balanced 4.4 mm Pentaconn output alongside a standard 3.5 mm unbalanced output. | upload.wikimedia.org/wikipedia/commons/4/43/Sony///NW-ZX300///DAP///headphone///outputs.jpg]\n\n### Disadvantages\nWhen using non-switching phone connectors to make balanced audio connections, the socket grounds the plug tip and ring when inserting or disconnecting the plug, and the ground mates last.\nThis 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.\nThis problem does not occur with XLR or when using gauge B which although it is of 0.25 in (6.35 mm) diameter has a smaller tip and a recessed ring so that the ground contact of the socket never touches the tip or ring of the plug.\nThis type was designed for balanced audio use, being the original telephone switchboard connector and is still common in broadcast, telecommunications and many professional audio applications where it is vital that permanent circuits being monitored are not interrupted by the insertion or removal of connectors.\nThis same tapered shape used in the gauge B plug can be seen also in aviation and military applications on various diameters of jack connector including the PJ-068 and Bantam plugs.\nThe more common straight-sided profile used in domestic and commercial applications and discussed in most of this article is known as gauge A.\nAlternatively, some switched audio jacks contain built-in isolated switches that only activate when the plug is fully inserted.\nThis can be used to avoid the insertion issue, for instance by wiring the connectors through a [double pole, double throw](https://bliptext.com/articles/double-pole-double-throw) switch that activates only upon full insertion.\nOr for instance by having the switch control a circuit that gracefully ramps up the audio once the plug is fully-inserted and mutes the audio when not fully-inserted.\n\n## Unbalanced audio\nPhone connectors with three conductors are also commonly used as unbalanced audio patch points (or insert points, or simply [inserts](https://bliptext.com/articles/insert-effects-processing)), with the output on many mixers found on the tip and the input on the ring.\nThis is often expressed as tip send, ring return.\nOlder mixers and some outboard gear have unbalanced insert points with ring send, tip return.\nIn 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.\nCombining send and return functions via single 1/4 in TRS connectors halves the space needed for insert jack fields which would otherwise require two jacks, one for send and one for return.\nIn some three-conductor TRS phone inserts, the concept is extended by using specially designed phone jacks that will accept a mono phone plug partly inserted to the first click and will then connect the tip to the signal path without breaking it.\nStandard TRS connectors may also be used in this way with varying success.\nIn some very compact equipment including [modular synthesizers](https://bliptext.com/articles/modular-synthesizer), 3.5 mm TS phone connectors are used for patch points.\n\n# Explanatory notes","current_revision":null,"created_by":"kACnuQmH5k9Nr5VNVEpVeg7XpvUmMctD","created_at":"2025-01-25T18:56:01.781Z","updated_at":"2025-01-25T18:56:01.781Z","search_vector":"'audio':3 'connector':2 'phone':1","search_content":" \n \n\n# \nA **phone connector** is a family of [cylindrically](https://bliptext.com/articles/cylinder)-shaped [electrical connectors](https://bliptext.com/articles/electrical-connectors) primarily for [analog](https://bliptext.com/articles/analog-signal) [audio signals](https://bliptext.com/articles/audio-signal).\nInvented in the late 19th century for telephone switchboards, the phone connector remains in use for interfacing wired [audio equipment](https://bliptext.com/articles/audio-equipment), such as headphones, [speakers](https://bliptext.com/articles/loudspeaker), microphones, [mixing consoles](https://bliptext.com/articles/mixing-console), and [electronic musical instruments](https://bliptext.com/articles/electronic-musical-instruments) (e.g. [electric guitars](https://bliptext.com/articles/electric-guitars), [keyboards](https://bliptext.com/articles/electronic-keyboard), and [effects units](https://bliptext.com/articles/effects-units)).\nA male connector (a plug), is mated into a female connector (a socket), though [other terminology](https://bliptext.com/articles/) is used.\nPlugs have 2 to 5 [electrical contacts](https://bliptext.com/articles/electrical-contacts).\nThe **tip** contact is indented with a groove.\nThe **sleeve** contact is nearest the (conductive or insulated) [handle](https://bliptext.com/articles/handle).\nContacts are [insulated](https://bliptext.com/articles/insulation-electric) from each other by a band of non-conductive material.\nBetween the tip and sleeve are 0 to 3 **ring** contacts.\nSince phone connectors have many uses, it is common to simply name the connector according its number of rings:\nThe sleeve is usually a [common ground](https://bliptext.com/articles/ground-electricity) reference [voltage](https://bliptext.com/articles/voltage) or return [current](https://bliptext.com/articles/electric-current) for signals in the [tip and any rings](https://bliptext.com/articles/tip-and-ring).\nThus, the number of transmittable [signals](https://bliptext.com/articles/signal) is less than the number of contacts.\nThe outside diameter of the sleeve is 6.35 mm for full-sized connectors, 3.5 mm for \"[mini](https://bliptext.com/articles/)\" connectors, and only 2.5 mm for \"sub-[mini](https://bliptext.com/articles/)\" connectors.\nRings are typically the same diameter as the sleeve.\n# [Phone plug mated in a phone socket. The plug's grooved tip is held firmly by the socket's spring tip contact. When not mated, this spring instead connects to the flat switch contact for detecting a plug. | upload.wikimedia.org/wikipedia/commons/8/83/Mated-plug-socket-switched.jpg]\n# [TS and TRS plugs of different sizes | upload.wikimedia.org/wikipedia/commons/c/c1/Phone-connectors-labeled.jpg]\n\n# Other terms\nThe 1902 International Library of Technology simply uses jack for the female and plug for the male connector.\nThe 1989 Sound Reinforcement Handbook uses phone jack for the female and phone plug for the male connector.\nRobert McLeish, who worked at the [BBC](https://bliptext.com/articles/bbc), uses jack or jack socket for the female and jack plug for the male connector in his 2005 book Radio Production.\nThe [American Society of Mechanical Engineers](https://bliptext.com/articles/american-society-of-mechanical-engineers), as of 2007, says the more fixed [electrical connector](https://bliptext.com/articles/electrical-connector) is the jack, while the less fixed connector is the plug, without regard to the [gender](https://bliptext.com/articles/gender-of-connectors-and-fasteners) of the connector contacts.\nThe [Institute of Electrical and Electronics Engineers](https://bliptext.com/articles/institute-of-electrical-and-electronics-engineers) in 1975 also made a standard that was withdrawn in 1997.\nThe intended application for a phone connector has also resulted in names such as audio jack, headphone jack, stereo plug, microphone jack, aux input, etc. Among audio engineers, the connector may often simply be called a quarter-inch to distinguish it from [XLR](https://bliptext.com/articles/xlr-connector), another frequently-used audio connector.\nThese naming variations are also used for the 3.5 mm connectors, which have been called mini-phone, mini-stereo, mini jack, etc.\n[RCA connectors](https://bliptext.com/articles/rca-connector) are differently-shaped, but confusingly are similarly-named as phono plugs and phono jacks (or in the UK, phono sockets).\n3.5 mm connectors are sometimes—counter to the connector manufacturers' nomenclature —referred to as mini phonos.\nConfusion also arises because phone jack and phone plug may sometimes refer to the [RJ11](https://bliptext.com/articles/rj11) and various older [telephone sockets and plugs](https://bliptext.com/articles/telephone-jack-and-plug) that connect wired telephones to wall outlets.\n\n# Historical development\nThe original 1/4 in version descends from as early as 1877 in [Boston](https://bliptext.com/articles/boston) when the first telephone switchboard was installed or 1878, when an early switchboard was used for the first commercial [manual telephone exchange](https://bliptext.com/articles/telephone-switchboard) in [New Haven](https://bliptext.com/articles/new-haven) created by [George W. Coy](https://bliptext.com/articles/george-w-coy).\nCharles E. Scribner filed a patent in 1878 to facilitate switchboard operation using his spring-jack switch.\nIn it, a conductive [lever](https://bliptext.com/articles/lever) pushed by a [spring](https://bliptext.com/articles/spring-device) is normally connected to one contact.\nBut when a cable with a conductive plug is inserted into a hole and makes contact with that lever, the lever pivots and breaks its normal connection.\nThe receptacle was called a jack-knife because of its resemblance to a pocket [clasp-knife](https://bliptext.com/articles/clasp-knife).\nThis is said to be the origin of calling the receptacle a jack.\nScribner filed a patent in 1880 which removes the lever and resembles the modern connector and made improvements to switchboard design in subsequent patents filed in 1882.\nHenry P. Clausen filed a patent in 1901 for improved construction of the telephone switchboard-plug with today's 1/4 inch TS form still used on audio equipment.\n[Western Electric](https://bliptext.com/articles/western-electric) was the manufacturing arm of the [Bell System](https://bliptext.com/articles/bell-system), and thus originated or refined most of the engineering designs, including the telephone jacks and plugs which were later adopted by other industries, including the [US military](https://bliptext.com/articles/us-military).\nBy 1907, Western Electric had designed a number of models for different purposes, including:\nBy 1950, the two main plug designs were:\nSeveral modern designs have descended from those earlier versions:\n# [Mated connectors in Scribner's patent 489,570 filed on December 27, 1880 | upload.wikimedia.org/wikipedia/commons/d/dd/Scribner///Phone-Connector///Patent///489570.png]\n# [Henry P. Clausen's 1901 patent | upload.wikimedia.org/wikipedia/commons/a/a8/Clausen-telephone-switchboard-plug-patent.png]\n# [227x227px | upload.wikimedia.org/wikipedia/commons/7/7f/Oldphoneplugs.jpg]\n# [220x220px | upload.wikimedia.org/wikipedia/commons/e/ee/2-conductor///male///TS///connectors.jpg]\n\n## Military variants\nU.S. military versions of the Western Electric plugs were initially specified in Amendment No.1, MIL-P-642, and included:\n\n## Miniature size\nThe 3.5 mm or miniature size was originally designed in the 1950s as two-conductor connectors for earpieces on [transistor radios](https://bliptext.com/articles/transistor-radio), and remains a standard still used today.\nThis roughly half-sized version of the original, popularized by the Sony EFM-117J radio (released in 1964), is still commonly used in portable applications and has a length of 15 mm. The three-conductor version became very popular with its application on the [Walkman](https://bliptext.com/articles/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.\nThere is also an EIA standard for 0.141-inch miniature phone jacks.\nThe 2.5 mm or sub-miniature sizes were similarly popularized on small portable electronics.\nThey often appeared next to a 3.5 mm microphone jack for a remote control on-off switch on early portable tape recorders; the microphone provided with such machines had the on-off switch and used a two-pronged connector with both the 3.5 and 2.5 mm plugs.\nThey were also used for low-voltage DC power input from wall adapters.\nIn the latter role, they were soon replaced by coaxial [DC power connectors](https://bliptext.com/articles/dc-power-connector).\n2.5 mm phone jacks have also been used as headset jacks on mobile telephones (see ).\nThe 1/8 in and 1/10 in sizes, approximately 3.5 mm and 2.5 mm respectively in mm, though those dimensions are only approximations.\nAll sizes are now readily available in two-conductor (un[balanced](https://bliptext.com/articles/balanced-audio) mono) and three-conductor ([balanced](https://bliptext.com/articles/balanced-audio) mono or un[balanced](https://bliptext.com/articles/balanced-audio) stereo) versions.\nFour-conductor versions of the 3.5 mm plug and jack are used for certain applications.\nA four-conductor version is often used in compact [camcorders](https://bliptext.com/articles/camcorder) and portable media players, providing stereo sound and composite analog video.\nIt is also used for a combination of stereo audio, a microphone, and controlling media playback, calls, volume and/or a [virtual assistant](https://bliptext.com/articles/virtual-assistant) on some [laptop computers](https://bliptext.com/articles/laptop-computers) and most [mobile phones](https://bliptext.com/articles/), and some handheld [amateur radio](https://bliptext.com/articles/amateur-radio) transceivers from [Yaesu](https://bliptext.com/articles/yaesu-brand).\nSome headphone amplifiers have used it to connect balanced stereo headphones, which require two conductors per audio channel as the channels do not share a common ground.\n\n## Broadcast usage\nBy the 1940s, broadcast radio stations were using Western Electric Code No. 103 plugs and matching jacks for patching audio throughout studios.\nThis connector was used because of its use in [AT&T](https://bliptext.com/articles/at-t)'s Long Line circuits for the distribution of audio programs over the radio networks' leased telephone lines.\nBecause of the large amount of space these patch panels required, the industry began switching to 3-conductor plugs and jacks in the late 1940s, using the WE Type 291 plug with WE type 239 jacks.\nThe type 291 plug was used instead of the standard type 110 switchboard plug because the location of the large bulb shape on this TRS plug would have resulted in both audio signal connections being shorted together for a brief moment while the plug was being inserted and removed.\nThe Type 291 plug avoids this by having a shorter tip.\n\n## Patch bay connectors\n[Professional audio](https://bliptext.com/articles/professional-audio) and the telecommunication industry use a 0.173 in diameter plug, associated with trademarked names including Bantam, TT, Tini-Telephone, and Tini-Tel.\nThey are not compatible with standard EIA RS-453/IEC 60603-11 1/4-inch jacks.\nIn addition to a slightly smaller diameter, they have a slightly different geometry.\nThe three-conductor TRS versions are capable of handling balanced signals and are used in professional audio installations.\nThough unable to handle as much power, and less [reliable](https://bliptext.com/articles/reliability-engineering) than a 6.35 mm jack, Bantam connectors are used for [mixing console](https://bliptext.com/articles/mixing-console) and outboard [patchbays](https://bliptext.com/articles/patchbay) in recording studio and [live sound](https://bliptext.com/articles/live-sound) applications, where large numbers of patch points are needed in a limited space.\nThe slightly different shape of Bantam plugs is also less likely to cause shorting as they are plugged in.\n\n## Less common\nA 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 in.\nThe socket versions of these can be used with normal phone plugs provided the plug bodies are not too large, but the plug version will only mate with two sockets at 5/8 inches centre spacing, or with line sockets, again with sufficiently small bodies.\nThese connectors are still used today in telephone company central offices on \"DSX\" patch panels for [DS1 circuits](https://bliptext.com/articles/digital-signal-1).\nA 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](https://bliptext.com/articles/in-flight-entertainment) system.\nPlugging a stereo plug into one of the two mono jacks typically results in the audio coming into only one ear.\nAdapters are available.\nA 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](https://bliptext.com/articles/world-war-ii-aircraft).\nThese have become rare.\nIt is physically possible to use a normal plug in a short socket, but a short plug will neither lock into a normal socket nor complete the tip circuit.\nLess 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 in inside diameter jacks for fire safety communication in public buildings.\n# [A dual 310 patch cable, two-pin phone plug | upload.wikimedia.org/wikipedia/commons/6/68/Aadoublejackplug.jpg]\n\n## Decline\n[Digital audio](https://bliptext.com/articles/digital-audio) is now common and may be transmitted via [USB sound cards](https://bliptext.com/articles/usb-sound-card), USB headphones, [Bluetooth](https://bliptext.com/articles/bluetooth), [display connectors with integrated sound](https://bliptext.com/articles/audio-and-video-interfaces-and-connectors) (e.g. [DisplayPort](https://bliptext.com/articles/displayport) and [HDMI](https://bliptext.com/articles/hdmi)).\nDigital devices may also have internal speakers and mics.\nThus the phone connector is sometimes considered redundant and a waste of space, particularly on thinner [mobile devices](https://bliptext.com/articles/mobile-devices).\nAnd while low-profile [surface-mount](https://bliptext.com/articles/surface-mount) sockets [waterproofed up to 1 meter](https://bliptext.com/articles/ip67) exist, removing the socket entirely facilitates [waterproofing](https://bliptext.com/articles/waterproofing).\nChinese phone manufacturers were early in not using a phone socket: first with [Oppo](https://bliptext.com/articles/oppo)'s Finder in July 2012 (which came packaged with [micro-USB](https://bliptext.com/articles/micro-usb) headphones and supported [Bluetooth headphones](https://bliptext.com/articles/bluetooth-headphones)), followed by [Vivo](https://bliptext.com/articles/vivo-technology-company)'s X5Max in 2014 and [LeEco](https://bliptext.com/articles/leeco) in April 2016 and [Lenovo](https://bliptext.com/articles/lenovo)'s [Moto Z](https://bliptext.com/articles/moto-z) in September 2016.\n[Apple](https://bliptext.com/articles/apple-inc)'s September 2016 announcement of the [iPhone 7](https://bliptext.com/articles/iphone-7) was initially mocked for removing the socket by other manufacturers like [Samsung](https://bliptext.com/articles/samsung-electronics) and Google who eventually followed suit.\nThe socket is also not present in some tablets and thin laptops (e.g. [Lenovo](https://bliptext.com/articles/lenovo) Duet [Chromebook](https://bliptext.com/articles/chromebook) and [Asus](https://bliptext.com/articles/asus) [ZenBook](https://bliptext.com/articles/zenbook) 13 in 2020 ).\n\n# Aviation and US military connectors\nThe US military uses a variety of phone connectors including 9/32-inch (0.281-inch, 7.14 mm) and 1/4-inch (0.25 inch, 6.35 mm) diameter plugs.\nCommercial and [general aviation](https://bliptext.com/articles/general-aviation) (GA) civil aircraft headsets often use a pair of phone connectors.\nA standard 1/4-inch (6.3 mm) 2 or 3-conductor plug, type PJ-055, is used for headphones.\nFor the microphone, a smaller 3/16-inch (0.206 inch / 5.23 mm) diameter 3-conductor plug, type PJ-068, is used.\nMilitary aircraft and civil helicopters have another type termed the U-174/U (Nexus TP-101), also known as U-93A/U (Nexus TP-102) and Nexus TP-120.\nThese are also known as US NATO plugs.\nThese have a 0.281 in diameter shaft with four conductors, allowing two for the headphones, and two for the microphone.\nAlso used is the U-384/U (Nexus TP-105), which has the same diameter as the U-174/U but is slightly longer and has 5 conductors instead of 4.\nThere is a confusingly similar four-conductor British connector, Type 671 (10H/18575), with a slightly larger diameter of 7.57 mm used for headsets in many UK military aircraft and often referred to as a UK NATO or European NATO connector.\n# [PJ-055 (top) and PJ-068 (bottom) General Aviation Audio Phone Connectors | upload.wikimedia.org/wikipedia/commons/2/24/PJ-055///and///PJ-068///Connectors.png]\n\n# General use\nIn 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.\nA considerable variety of line plugs and panel sockets is available, including plugs suiting various cable sizes, right-angle plugs, and both plugs and sockets in a variety of price ranges and with current capacities up to 15 [amperes](https://bliptext.com/articles/ampere) for certain heavy-duty 1/4 in versions intended for [loudspeaker](https://bliptext.com/articles/loudspeaker) connections.\nCommon uses of phone plugs and their matching sockets include:\n# [A 3.5 mm phone connector | upload.wikimedia.org/wikipedia/commons/1/16/TRS///connector.JPG]\n# [A 3.5 mm 4-conductor TRRS phone connector | upload.wikimedia.org/wikipedia/commons/3/3b/3.5mm.jpg]\n# [A 3.5 mm 5-conductor TRRRS phone connector | upload.wikimedia.org/wikipedia/commons/1/11/Klinkenstecker///5-polig.jpg]\n\n# Computer sound\nAny number of 3.5 mm sockets for input and output may be found on [personal computers](https://bliptext.com/articles/personal-computers), either from [integrated sound hardware](https://bliptext.com/articles/sound-card) common on [motherboards](https://bliptext.com/articles/motherboards) or from insertable [sound cards](https://bliptext.com/articles/sound-cards).\nThe [1999 PC System Design Guide's color code](https://bliptext.com/articles/pc-system-design-guide) for 3.5 mm TRS sockets is common, which assigns pink for microphone, light blue for line in, and lime for line level.\n[AC'97](https://bliptext.com/articles/ac-97) and its 2004 successor [Intel High Definition Audio](https://bliptext.com/articles/intel-high-definition-audio) have been widely adopted specifications that, while not mandating physical sockets, do provide specifications for a [front panel connector](https://bliptext.com/articles/intel-high-definition-audio) with pin assignments for two ports with jack detection.\nFront panels commonly have a stereo output socket for headphones and (slightly less commonly) a stereo input socket for a mic.\nThe back panel may have additional sockets, most commonly for line out, mic, line in, and less commonly for multiple [surround sound](https://bliptext.com/articles/surround-sound) outs.\n[Laptops](https://bliptext.com/articles/laptops) and [tablets](https://bliptext.com/articles/tablet-computer) tend to have fewer sockets than [desktops](https://bliptext.com/articles/desktop-computer) due to size constraints.\n# [221x221px | upload.wikimedia.org/wikipedia/commons/b/bf/Desktop///sound///connectors.svg]\n# [This connector's color indicates it should plug into a computer's line audio out socket | upload.wikimedia.org/wikipedia/commons/8/8b/Audio-TRS-Mini-Plug.jpg]\n\n## Microphone power\nSome computers include a 3.5 mm TRS socket for mono microphone that delivers a 5 V [bias voltage](https://bliptext.com/articles/bias-voltage) on the ring to power an [electret microphone](https://bliptext.com/articles/electret-microphone)'s integrated [buffer amplifier](https://bliptext.com/articles/buffer-amplifier), though details depend on the manufacturer.\nThe [Apple](https://bliptext.com/articles/apple-inc) [PlainTalk](https://bliptext.com/articles/plaintalk) microphone socket is a historical variant that accepts either a 3.5 mm [line](https://bliptext.com/articles/line-level) input or an elongated 3.5 mm TRS plug whose tip carries the amplifier's power.\n\n## TRRS headset sockets\nSome newer computers, especially laptops, have 3.5 mm TRRS headset sockets, which are compatible with phone headsets and may be distinguished by a headset icon instead of the usual headphones or microphone icons.\nThese are particularly used for [voice over IP](https://bliptext.com/articles/voice-over-ip).\n\n## Surround sound\nSound cards that output [5.1 surround sound](https://bliptext.com/articles/5-1-surround-sound) have three sockets to accommodate six channels: front left and right; surround left and right; and center and subwoofer.\n6.1 and 7.1 channel sound cards from Creative Labs, however, use a single three-conductor socket (for the front speakers) and two four-conductor sockets.\nThis is to accommodate rear-center (6.1) or rear left and right (7.1) channels without the need for additional sockets on the sound card.\n\n## Combined TRS and TOSLINK\nSome portable computers have a combined 3.5 mm TRS/[TOSLINK](https://bliptext.com/articles/toslink) jack, supporting stereo audio output using either a TRS connector or [TOSLINK](https://bliptext.com/articles/toslink) (stereo or 5.1 [Dolby Digital](https://bliptext.com/articles/dolby-digital)/[DTS](https://bliptext.com/articles/dts-sound-system)) digital output using a suitable optical adapter.\nMost iMac computers have this digital/analog combo output feature as standard, with early MacBooks having two ports, one for analog/digital audio input and the other for output.\nSupport for input was dropped on various later models\n\n# Compatibility for different numbers of rings\nThe original application for the 6.35 mm (1/4 in) phone jack was in manual telephone exchanges.\nMany different configurations of these phone plugs were used, some accommodating five or more conductors, with several tip profiles.\nOf 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](https://bliptext.com/articles/microphone), electric guitars, [headphones](https://bliptext.com/articles/headphones), [loudspeakers](https://bliptext.com/articles/loudspeaker), and other [audio equipment](https://bliptext.com/articles/audio-equipment).\nWhen a three-conductor version of the 6.35 mm plug was introduced for use with stereo headphones, it was given a sharper tip profile to make it possible to manufacture jacks that would accept only stereo plugs, to avoid short-circuiting the right channel of the amplifier.\nThis 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.\nMost 6.35 mm plugs, mono or stereo, now have the profile of the original stereo plug, although a few rounded mono plugs are still produced.\nThe profiles of stereo miniature and sub-miniature plugs have always been identical to the mono plugs of the same size.\nThe results of this physical compatibility are:\nEquipment aware of this possible shorting allows, for instance:\nSome devices for an even higher number of rings might possibly be [backwards-compatible](https://bliptext.com/articles/backwards-compatible) with an opposite-gendered device with fewer rings, or may cause damage.\nFor 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.\nConversely, those TRRS headsets can plug into TRS sockets, in which case its speakers may still work even though its mic won't work (the mic's signal contact will be disconnected).\nBecause 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.\nThis can result in a contact in the socket bridging (shorting) the ring and sleeve contacts on a phone connector.\n\n# Video\nEquipment requiring video with stereo audio input or output sometimes uses 3.5 mm TRRS connectors.\nTwo incompatible variants exist, of 15 mm and 17 mm length, and using the wrong variant may either simply not work, or could cause physical damage.\nAttempting to fully insert the longer (17 mm) plug into a receptacle designed for the shorter (15 mm) plug may damage the receptacle, and may damage any electronics located immediately behind the receptacle.\nHowever, partially inserting the plug will work as the tip/ring/ring distances are the same for both variants.\nA shorter plug in a socket designed for the longer connector may not be retained firmly and may result in wrong signal routing or a short circuit inside the equipment (e.g. the plug tip may cause the contacts inside the receptacle – tip/ring 1, etc. – to short together).\nThe shorter 15 mm TRRS variant is more common and physically compatible with standard 3.5 mm TRS and TS connectors.\n# [Different length 3.5 mm TRRS connectors | upload.wikimedia.org/wikipedia/commons/e/ed/TRRS///3.5mm///-///2///length///variants.jpg]\n\n# Recording equipment\nMany small video cameras, laptops, recorders and other consumer devices use a 3.5 mm microphone connector for attaching a microphone to the system.\nThese fall into three categories:\n# [Stereo devices which use \"plug-in power\": the electret capsules are wired in this way. | upload.wikimedia.org/wikipedia/commons/5/5e/Jackplug-wiring.svg]\n\n# Mobile devices\nThree- or four-conductor (TRS or TRRS) 2.5 mm and 3.5 mm sockets were common on older cell phones and [smartphones](https://bliptext.com/articles/smartphone) 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).\nThese are used both for [handsfree](https://bliptext.com/articles/handsfree) [headsets](https://bliptext.com/articles/headset-audio) and for stereo headphones.\n3.5 mm TRRS (stereo-plus-mic) sockets became particularly common on [smartphones](https://bliptext.com/articles/smartphones), and have been used by Nokia and others since 2006, and as mentioned in the compatibility section, they are often compatible with standard 3.5 mm stereo headphones.\nMany computers, especially laptops, also include a TRRS headset socket compatible with the headsets intended for smartphones.\nThe four conductors of a TRRS connector are assigned to different purposes by different manufacturers.\nAny 3.5 mm plug can be plugged mechanically into any socket, but many combinations are electrically incompatible.\nFor example, plugging TRRS headphones into a TRS headset socket, a TRS headset into a TRRS socket, or plugging TRRS headphones from one manufacturer into a TRRS socket from another may not function correctly, or at all.\nMono audio will usually work, but stereo audio or the microphone may not work, or the pause/play controls may be inactive, as is common when trying to use headphones with controls for iPhones on an Android device, or vice versa.\n# [All iPhone models from the first generation to the 6S and SE (first generation) use a four-conductor (TRRS) phone connector (center) for a wired headset. | upload.wikimedia.org/wikipedia/commons/3/3b/iPod///and///iPhone///audio///plugs.JPG]\n\n## TRRS standards\nTwo different forms are frequently found.\nBoth place left audio on the tip and right audio on the first ring, same as stereo connectors.\nThey differ in the placement of the microphone and return contacts.\nThe [OMTP](https://bliptext.com/articles/omtp) standard places the ground return on the sleeve and the microphone on the second ring.\nIt has been accepted as a national Chinese standard YDT 1885–2009.\nIn the West, it is mostly used on older devices, such as older Nokia mobiles, older [Samsung](https://bliptext.com/articles/samsung) smartphones, and some [Sony Ericsson](https://bliptext.com/articles/sony-ericsson) phones.\nIt is widely used in products meant for the Chinese market.\nHeadsets using this wiring are sometimes indicated by black plastic separators between the rings.\nThe [CTIA](https://bliptext.com/articles/ctia-organization)/[AHJ](https://bliptext.com/articles/american-headset-jack) standard reverses these contacts, putting the microphone on the sleeve.\nIt is used by [Apple](https://bliptext.com/articles/apple-inc)'s [iPhone](https://bliptext.com/articles/iphone) line until the [6S](https://bliptext.com/articles/iphone-6s) and [SE (1st)](https://bliptext.com/articles/iphone-se-1st-generation).\nIn the West, these products made it the de facto TRRS standard.\nIt is now used by [HTC](https://bliptext.com/articles/htc) devices, recent [Samsung](https://bliptext.com/articles/samsung), [Nokia](https://bliptext.com/articles/nokia), and [Sony phones](https://bliptext.com/articles/sony-mobile), among others.\nIt has the disadvantage that the microphone gets shorted to ground if the device has a metal body and the sleeve has a flange, touching the body.\nHeadsets using this wiring are sometimes indicated by white plastic separators between the rings.\nIf a CTIA headset is connected to an OMTP device, the missing ground effectively connects the speakers in series, out-of-phase.\nThis removes the singer's voice on typical popular music recordings, which place the singers in the center.\nIf the main microphone button is held down, shorting across the microphone and restoring ground, the correct sound may be audible.\nThe 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.\n3-pole 3.5 mm TRS connectors are defined in JIS C 6560.\nSee also JIS C 5401 and IEC 60130-8.\n[Apple](https://bliptext.com/articles/apple-inc)'s [iPod Shuffle 2G](https://bliptext.com/articles/ipod-shuffle) reuses its TRRS socket not just for audio but also for charging and syncing over [USB](https://bliptext.com/articles/usb) when docked.\n\n### Interoperability\nThe USB Type-C Cable and Connector Specification specifies a mapping from a [USB-C](https://bliptext.com/articles/usb-c) jack to a 4-pole TRRS jack, for the use of headsets, and supports both CTIA and OMTP (YD/T 1885–2009) modes.\nSome devices transparently handle many jack standards, and there are hardware implementations of this available as components.\nThis is accomplished in some cases by applying a voltage to the sleeve and second ring to detect the wiring.\nThe last two conductors may then be switched to allow a device made to one standard to be used with a headset made to the other.\n\n## TRRRS standards\nA TRRRS standard for 3.5 mm connectors was developed by ITU-T.\nThe standard, called P.382 (formerly P.MMIC), outlines technical requirements and test methods for a 5-conductor socket and plug configuration.\nCompared to the TRRS standard, TRRRS provides one extra conductor that can be used for connecting a second microphone or providing power to or from the audio accessory.\nP.382 requires compliant sockets and plugs to be backward compatible with legacy TRRS and TRS connectors.\nTherefore, P.382-compliant TRRRS connectors should allow for seamless integration when used on new products.\nTRRRS 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.\nIt was commonly found on [Sony](https://bliptext.com/articles/sony) phones starting with the [Xperia Z1](https://bliptext.com/articles/xperia-z1)-[XZ1](https://bliptext.com/articles/sony-xperia-xz1) and [Xperia 1 II](https://bliptext.com/articles/xperia-1-ii).\nAnother TRRRS standard for 4.4 mm connectors following JEITA RC-8141C was introduced in 2015 and is used for [balanced audio](https://bliptext.com/articles/balanced-audio) connections, in particular for [headphone](https://bliptext.com/articles/headphone) cables.\nThis connector is often called a **Pentaconn** connector following the brand name of Nippon DICS (NDICS).\nIt is used by some Sony products like the [M1Z](https://bliptext.com/articles/m1z) Walkman of their Signature series and by some [Sennheiser](https://bliptext.com/articles/sennheiser) products like the [HD 820](https://bliptext.com/articles/hd-820) headphone or the HDV 820 DAC headphone amplifier.\n\n# Switch contacts\nPanel-mounted jacks may include switch contacts.\nMost commonly, a mono jack is provided with one normally closed (NC) contact, which is connected to the tip (live) connection when no plug is in the socket, and disconnected when a plug is inserted.\nStereo sockets commonly provide two such NC contacts, one for the tip (left channel) and one for the ring or collar (right channel).\nSome jacks also have such a connection on the sleeve.\nAs this contact is usually ground, it is not much use for signal switching but could be used to indicate to electronic circuitry that the jack is in use.\nLess commonly, jacks may feature normally open (NO) or change-over contacts or the switch contacts may be isolated from the connector signals.\nThe original purpose of these contacts was for switching in telephone exchanges, for which there were many patterns.\nTwo sets of change-over contacts, isolated from the connector contacts, were common.\nThe more recent pattern of one NC contact for each signal path, internally attached to the connector contact, stems from their use as headphone jacks.\nIn many amplifiers and equipment containing them, such as electronic organs, a headphone jack is provided that disconnects the loudspeakers when in use.\nThis is done by means of these switch contacts.\nIn other equipment, a dummy load is provided when the headphones are not connected.\nThis is also easily provided by means of these NC contacts.\nOther uses for these contacts have been found.\nOne is to interrupt a signal path in a mixing console to [insert](https://bliptext.com/articles/insert-effects-processing) an effects processor.\nThis 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.\nA similar arrangement is used in patch panels for normalization (see ).\nWhere a 3.5 mm or 2.5 mm jack is used as a DC power inlet connector, a switch contact may be used to disconnect an internal battery whenever an external power supply is connected, to prevent incorrect recharging of the battery.\nTo eliminate the need for a separate power switch, a standard stereo jack is used on most battery-powered guitar [effects pedals](https://bliptext.com/articles/effects-pedal).\nThe internal battery has its negative terminal wired to the sleeve contact of the jack.\nWhen the user plugs in a two-conductor (mono) plug, the resulting short circuit between the sleeve and ring connects an internal battery to the unit's circuitry, ensuring that it powers up or down automatically whenever a signal lead is inserted or removed.\n# [Miniature phone plugs and jacks. All are 3.5 mm except the gold-plated plug, which is 2.5 mm. One of the 3.5 mm jacks is two-conductor and the others are three conductor. In this collection the tan-colored jacks have normally-closed switches. | upload.wikimedia.org/wikipedia/commons/1/1b/Small///jack///plugs.jpg]\n\n# Design\nThe connector assembly is usually made by one or more hollow and one solid pin.\nThe jack is then assembled with pins separated by an [insulating](https://bliptext.com/articles/insulator-electricity) material.\nConnectors that are tarnished, or that were not manufactured within tight tolerances, are prone to cause poor connections.\nDepending upon the surface material of the connectors, tarnished ones can be cleaned with a burnishing agent (for solid brass contacts typical) or contact cleaner (for plated contacts).\n# [Examples of jack configurations, oriented so the plug enters from the right. The most common circuit configurations are the simple mono and stereo jacks (A and B); however, there are a great number of variants manufactured. \n \n A two-conductor TS phone connector. The connection to the sleeve is the rectangle towards the right, and the connection to the tip is the line with the notch. Wiring connections are illustrated as white circles. \n A three-conductor TRS phone connector. The upper connector is the tip, as it is farther away from the sleeve. The sleeve is shown connected directly to the chassis, a typical configuration for a balanced connection. Some jacks use plastic, to isolate the sleeve from the chassis, and provide a separate sleeve connection point, as in A. \n This three-conductor jack has two isolated SPDT switches activated by a plug going into the jack, which disconnects one throw and connects the other. The white arrowheads indicate a mechanical connection, while the black arrowheads indicate an electrical connection. This configuration is useful for a device that turns on when a plug is inserted, and off otherwise, with the power routed through the switches. \n This three-conductor jack has two normally closed switches connected to the contacts themselves. This is useful for patch panel normalization. Another common use is as stereo headphone jack that shuts off the default output (speakers) when the connector is plugged in. \n | upload.wikimedia.org/wikipedia/commons/7/77/Phone///Jack///Symbols.svg]\n# [ Sleeve: Usually ground Ring: Right-hand channel for stereo signals, negative polarity for balanced mono signals, power supply for power-using mono signal sources \n Tip: Left-hand channel for stereo signals, positive polarity for balanced mono signals, signal line for unbalanced mono signals Insulating rings \n | upload.wikimedia.org/wikipedia/commons/9/93/Jack///plug.png]\n\n# Audio signals\n\n## Balanced audio\nWhen a phone connector is used to make a [balanced audio](https://bliptext.com/articles/balanced-audio) connection, the two active conductors are used for [differential](https://bliptext.com/articles/differential-signaling) versions of a monaural signal.\nThe ring, used for the right channel in stereo systems, is used instead for the inverting input.\n\n### Advantages\nWhere space is a premium, TRS connectors offer a more compact alternative to [XLR connectors](https://bliptext.com/articles/xlr-connector), and so are common in small audio [mixing desks](https://bliptext.com/articles/mixing-desk).\nAnother advantage offered by TRS connectors used for balanced microphone inputs is that a standard unbalanced signal lead using a TS phone jack can simply be plugged into such an input.\nThe inverting input on the ring contact gets correctly grounded when it makes contact with the plug body.\n# [The Sony Walkman NW-ZX300 has a balanced 4.4 mm Pentaconn output alongside a standard 3.5 mm unbalanced output. | upload.wikimedia.org/wikipedia/commons/4/43/Sony///NW-ZX300///DAP///headphone///outputs.jpg]\n\n### Disadvantages\nWhen using non-switching phone connectors to make balanced audio connections, the socket grounds the plug tip and ring when inserting or disconnecting the plug, and the ground mates last.\nThis 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.\nThis problem does not occur with XLR or when using gauge B which although it is of 0.25 in (6.35 mm) diameter has a smaller tip and a recessed ring so that the ground contact of the socket never touches the tip or ring of the plug.\nThis type was designed for balanced audio use, being the original telephone switchboard connector and is still common in broadcast, telecommunications and many professional audio applications where it is vital that permanent circuits being monitored are not interrupted by the insertion or removal of connectors.\nThis same tapered shape used in the gauge B plug can be seen also in aviation and military applications on various diameters of jack connector including the PJ-068 and Bantam plugs.\nThe more common straight-sided profile used in domestic and commercial applications and discussed in most of this article is known as gauge A.\nAlternatively, some switched audio jacks contain built-in isolated switches that only activate when the plug is fully inserted.\nThis can be used to avoid the insertion issue, for instance by wiring the connectors through a [double pole, double throw](https://bliptext.com/articles/double-pole-double-throw) switch that activates only upon full insertion.\nOr for instance by having the switch control a circuit that gracefully ramps up the audio once the plug is fully-inserted and mutes the audio when not fully-inserted.\n\n## Unbalanced audio\nPhone connectors with three conductors are also commonly used as unbalanced audio patch points (or insert points, or simply [inserts](https://bliptext.com/articles/insert-effects-processing)), with the output on many mixers found on the tip and the input on the ring.\nThis is often expressed as tip send, ring return.\nOlder mixers and some outboard gear have unbalanced insert points with ring send, tip return.\nIn 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.\nCombining send and return functions via single 1/4 in TRS connectors halves the space needed for insert jack fields which would otherwise require two jacks, one for send and one for return.\nIn some three-conductor TRS phone inserts, the concept is extended by using specially designed phone jacks that will accept a mono phone plug partly inserted to the first click and will then connect the tip to the signal path without breaking it.\nStandard TRS connectors may also be used in this way with varying success.\nIn some very compact equipment including [modular synthesizers](https://bliptext.com/articles/modular-synthesizer), 3.5 mm TS phone connectors are used for patch points.\n\n# Explanatory notes","revisionCount":0},"hasMore":false,"nextCursor":null}

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