Aphone connector is a family ofcylindrically-shapedelectrical connectors primarily foranalogaudio signals. Invented in the late 19th century fortelephone switchboards, the phone connector remains in use for interfacing wiredaudio equipment, such asheadphones,speakers,microphones,mixing consoles, andelectronic musical instruments (e.g.electric guitars,keyboards, andeffects units). Amale connector (a plug), is mated into afemale connector (a socket), thoughother terminology is used.
Plugs have 2 to 5electrical contacts. Thetip contact is indented with a groove. Thesleeve contact is nearest the (conductive orinsulated)handle.[1] Contacts are insulated from each other by a band of non-conductive material. Between the tip and sleeve are 0 to 3ring contacts. Since phone connectors have many uses, it is common to simply name the connector according to its number of rings:
| Abbreviation (full name) | Contacts | Typical uses | Plug appearance |
|---|---|---|---|
| TS (tip sleeve) | 2 | mono audio |  |
| TRS (tip ring sleeve) | 3 | stereo audio |  |
| mono audio (balanced) | |||
| MIDI[2] | |||
| TRRS (tip ring ring sleeve) | 4 | stereo headset with mono microphone |  |
| video with stereo audio | |||
| TRRRS (tip ring ring ring sleeve) | 5 | stereo audio (balanced) |  |
The sleeve isusually acommon ground referencevoltage or returncurrent for signals in thetip and any rings. Thus, the number of transmittablesignals is less than the number of contacts.
The outside diameter of the sleeve is 6.35 millimetres (1⁄4 inch) for full-sized connectors,3.5 mm (1⁄8 in) for "mini" connectors, and only2.5 mm (1⁄10 in) for "sub-mini" connectors. Rings are typically the same diameter as the sleeve.
The 1902International Library of Technology simply usesjack for the female andplug for the male connector.[3] The 1989Sound Reinforcement Handbook usesphone jack for the female andphone plug for the male connector.[4] Robert McLeish, who worked at theBBC, usesjack orjack socket for the female andjack plug for the male connector in his 2005 bookRadio Production.[5] TheAmerican Society of Mechanical Engineers, as of 2007, says the more fixedelectrical connector is the jack, while the less fixed connector is the plug,without regard to thegender of the connector contacts.[6] TheInstitute of Electrical and Electronics Engineers in 1975 also made a standard that was withdrawn in 1997.[7]
The intended application for a phone connector has also resulted in names such asaudio jack,headphone jack,stereo plug,microphone jack,aux input, etc. Among audio engineers, the connector may often simply be called aquarter-inch to distinguish it fromXLR, another frequently used audio connector. These naming variations are also used for the 3.5 mm connectors, which have been calledmini-phone,mini-stereo,mini jack, etc.
RCA connectors are differently shaped, but confusingly are similarly named asphono plugs andphono jacks (or in the UK,phono sockets). 3.5 mm connectors are sometimes—counter to the connector manufacturers' nomenclature[8]—referred to asmini phonos.[9]
Confusion also arises because phone jack and phone plug may sometimes refer to theRJ11 and various oldertelephone sockets and plugs that connect wired telephones to wall outlets.
The original1⁄4-inch (6.35 mm) version descends from as early as 1877 inBoston when the first telephone switchboard was installed[10] or 1878, when an early switchboard was used for the first commercialmanual telephone exchange[11][12] inNew Haven created byGeorge W. Coy.[13][14]
Charles E. Scribner filed a patent[15] in 1878 to facilitate switchboard operation using hisspring-jack switch. In it, a conductivelever pushed by aspring is normally connected to one contact. But 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. The receptacle was called a jack-knife because of its resemblance to a pocketclasp-knife.[16] This is said to be the origin of calling the receptacle ajack. Scribner filed a patent[17] in 1880 which removes the lever and resembles the modern connector and made improvements to switchboard design in subsequent patents[18][19] filed in 1882.
Henry P. Clausen filed a patent[20] in 1901 for improved construction of thetelephone switchboard-plug with today's1⁄4 inch TS form still used on audio equipment.
Western Electric was the manufacturing arm of theBell 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 theUS military.
By 1907, Western Electric had designed a number of models for different purposes, including:[21]
| Code No. | Description |
|---|---|
| 47 | 2-conductor plugs for use with type 3, 91, 99, 102, 103, 108, and 124 jacks—used for switchboards |
| 85 | 3-conductor plugs for use with type 77 jacks—used for the operator's head telephone |
| 103 | twin 2-conductor plugs for use with type 91, and type 99 jacks—used for the operator's head telephone and chest transmitter (microphone) |
| 109 | 3-conductor plugs for use with jack 92 on telephone switchboards (with the same basic shape as the modern Bantam plugs) |
| 110 | 3-conductor plug for use with jacks 49, 117, 118, 140, and 141 on switchboards |
| 112 | twin 2-conductor plug for use with jacks 91 and 99—used for the operator's head telephone and chest, with a transmitter cutout key (microphone mute) |
| 116 | 1-conductor plug for use with cordless jack boxes |
| 126 | 3-conductor plug for use with type 132 and type 309 jacks on portable street railway sets |
By 1950, the two main plug designs were:
Several modern designs have descended from those earlier versions:
U.S. military versions of the Western Electric plugs were initially specified in Amendment No.1, MIL-P-642, and included:
The 3.5 mm orminiature size was originally designed in the 1950s as two-conductor connectors for earpieces ontransistor radios, and remains a standard still used today.[24] This roughly half-sized version of the original, popularized by the Sony EFM-117J radio (released in 1964),[25][26][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 theWalkman 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. There is also an EIA standard for 0.141-inch miniature phone jacks.
The 2.5 mm orsub-miniature sizes were similarly popularized on small portable electronics. They 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. They were also used for low-voltage DC power input from wall adapters. In the latter role, they were soon replaced by coaxialDC power connectors. 2.5 mm phone jacks have also been used as headset jacks on mobile telephones (see§ Mobile devices).
The1⁄8 in and1⁄10 in sizes, approximately 3.5 mm and 2.5 mm respectively in mm, though those dimensions are only approximations.[27] All sizes are now readily available in two-conductor (unbalanced mono) and three-conductor (balanced mono or unbalanced stereo) versions.
Four-conductor versions of the 3.5 mm plug and jack are used for certain applications. A four-conductor version is often used in compactcamcorders 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 avirtual assistant on somelaptop computers and mostmobile phones,[28] and some handheldamateur radio transceivers fromYaesu.[29] Some 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.[30]
By the 1940s, broadcast radio stations were using Western Electric Code No. 103 plugs and matching jacks for patching audio throughout studios. This connector was used because of its use inAT&T's Long Line circuits for the distribution of audio programs over the radio networks' leased telephone lines.[citation needed] Because 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. The 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. The Type 291 plug avoids this by having a shorter tip.[31]
Professional audio and the telecommunication industry use a 0.173 in (4.4 mm) diameter plug, associated with trademarked names includingBantam, TT, Tini-Telephone, and Tini-Tel. They are not compatible with standard EIA RS-453/IEC 60603-111⁄4-inch jacks. In addition to a slightly smaller diameter, they have a slightly different geometry.[32] The three-conductor TRS versions are capable of handling balanced signals and are used in professional audio installations. Though unable to handle as much power, and lessreliable than a6.35 mm (1⁄4 in) jack,[33] Bantam connectors are used formixing console and outboardpatchbays in recording studio andlive sound applications, where large numbers of patch points are needed in a limited space.[32] The slightly different shape of Bantam plugs is also less likely to cause shorting as they are plugged in.[citation needed]
A two-pin version, known to the telecom industry as a "310 connector", consists of two1⁄4-inch phone plugs at a centre spacing of5⁄8 inch (16 mm). The 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 at5⁄8 inches centre spacing, or with line sockets, again with sufficiently small bodies. These connectors are still used today in telephone company central offices on "DSX" patch panels forDS1 circuits. A similar type of 3.5 mm connector is often used in the armrests of older aircraft, as part of the on-boardin-flight entertainment system. Plugging a stereo plug into one of the two mono jacks typically results in the audio coming into only one ear. Adapters are available.
A short-barrelled version of the phone plug was used for 20th-century high-impedance mono headphones, and in particular those used inWorld War II aircraft. These have become rare. It 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.
Less commonly used sizes, both diameters and lengths, are also available from some manufacturers, and are used when it is desired to restrict the availability of matching connectors, such as 0.210-inch (5.3 mm) inside diameter jacks for fire safety communication in public buildings.[a]
While phone connectors remain a standard connector type in some fields, such as desktop computers, musical instrument amplification,[35] and live audio and recording equipment,[36][37] they have been removed from many smartphones.[38]
Digital audio is now common and may be transmitted viaUSB sound cards, USB headphones,Bluetooth,display connectors with integrated sound (e.g.DisplayPort andHDMI). Digital devices may also have internal speakers and mics. Thus the phone connector is sometimes considered redundant and a waste of space, particularly on thinnermobile devices. And while low-profilesurface-mount socketswaterproofed up to 1 meter exist,[39] removing the socket entirely facilitateswaterproofing.[40]
Chinese phone manufacturers were early in not using a phone socket: first withOppo's Finder in July 2012 (which came packaged withmicro-USB headphones and supportedBluetooth headphones), followed byVivo's X5Max in 2014 andLeEco in April 2016 andLenovo'sMoto Z in September 2016.[41]Apple's September 2016 announcement of theiPhone 7 was initially mocked for removing the socket by other manufacturers likeSamsung and Google who eventually followed suit.[42] The socket is also not present in some tablets and thin laptops (e.g.Lenovo DuetChromebook andAsusZenBook 13 in 2020[43]).
The US military uses a variety of phone connectors including9⁄32-inch (0.281-inch, 7.14 mm) and1⁄4-inch (0.25 inch, 6.35 mm) diameter plugs.[44]
Commercial andgeneral aviation (GA) civil aircraft headsets often use a pair of phone connectors. A standard1⁄4-inch (6.3 mm) 2 or 3-conductor plug, type PJ-055, is used for headphones. For the microphone, a smaller3⁄16-inch (0.206 inch / 5.23 mm) diameter 3-conductor plug, type PJ-068, is used.
Military aircraft and civil helicopters have another type termed the U-174/U (Nexus TP-101),[45] also known as U-93A/U (Nexus TP-102)[46] and Nexus TP-120.[47] These are also known asUS NATO plugs. These have a 0.281 in (7.1 mm) diameter shaft with four conductors, allowing two for the headphones, and two for the microphone. Also 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.[48][49]
There is a confusingly similar four-conductor British connector, Type 671 (10H/18575), with a slightly larger diameter of 7.57 mm (0.298 in)[50] used for headsets in many UK military aircraft and often referred to as aUK NATO orEuropean NATO connector.[51]
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. A 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 15amperes for certain heavy-duty1⁄4 in versions intended forloudspeaker connections.[52]
Common uses of phone plugs and their matching sockets include:
Any number of 3.5 mm sockets for input and output may be found onpersonal computers, either fromintegrated sound hardware common onmotherboards or from insertablesound cards. The1999 PC System Design Guide's color code for 3.5 mm TRS sockets is common, which assigns pink formicrophone, light blue forline in, and lime forline level.AC'97 and its 2004 successorIntel High Definition Audio have been widely adopted specifications that, while not mandating physical sockets, do provide specifications for afront panel connector with pin assignments for two ports with jack detection. Front panels commonly have a stereo output socket for headphones and (slightly less commonly) a stereo input socket for a mic. The back panel may have additional sockets, most commonly forline out,mic,line in, and less commonly for multiplesurround sound outs.Laptops andtablets tend to have fewer sockets thandesktops due to size constraints.
Some computers include a 3.5 mm TRS socket for mono microphone that delivers a 5 Vbias voltage on the ring to power anelectret microphone's integratedbuffer amplifier, though details depend on the manufacturer.[53] TheApplePlainTalk microphone socket is a historical variant that accepts either a 3.5 mmline input or an elongated 3.5 mm TRS plug whose tip carries the amplifier's power.
Some 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. These are particularly used forvoice over IP.
Sound cards that output5.1 surround sound have three sockets to accommodate six channels: front left and right; surround left and right; and center and subwoofer. 6.1 and 7.1 channel sound cards from Creative Labs, however, use a single three-conductor socket (for thefront speakers) and two four-conductor sockets.[b] This 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.
Some portable computers have a combined 3.5 mm TRS/TOSLINK jack, supporting stereo audio output using either a TRS connector or TOSLINK (stereo or 5.1Dolby Digital/DTS) digital output using a suitable optical adapter. Most 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. Support for input was dropped on various later models[54][55]
The original application for the 6.35 mm (1⁄4 in) phone jack was in manual telephone exchanges.[56] Many different configurations of these phone plugs were used, some accommodating five or more conductors, with several tip profiles. 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 withmicrophones, electric guitars,headphones,loudspeakers, and otheraudio equipment.
When 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. 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. Most 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. The profiles of stereo miniature and sub-miniature plugs have always been identical to the mono plugs of the same size.
The results of this physical compatibility are:
Equipment aware of this possible shorting allows, for instance:
Some devices for an even higher number of ringsmight possibly bebackwards-compatible with an opposite-gendered device with fewer rings, or may cause damage. 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. Conversely, 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).[57]
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. This can result in a contact in the socket bridging (shorting) the ring and sleeve contacts on a phone connector.
Equipment requiring video with stereo audio input or output sometimes uses 3.5 mm TRRS connectors. Two incompatible variants exist, of 15 millimetres (0.59 in) and 17 mm (0.67 in) length, and using the wrong variant may either simply not work, or could cause physical damage.
Attempting 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. However, partially inserting the plug will work as the tip/ring/ring distances are the same for both variants.
A 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).
The shorter 15 mm TRRS variant is more common and physically compatible with standard 3.5 mm TRS and TS connectors.
Many small video cameras, laptops, recorders and other consumer devices use a 3.5 mm microphone connector for attaching a microphone to the system. 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 andsmartphones 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). These are used both forhandsfreeheadsets and for stereo headphones.
3.5 mm TRRS (stereo-plus-mic) sockets became particularly common onsmartphones, 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. Many computers, especially laptops, also include a TRRS headset socket compatible with the headsets intended for smartphones.
The four conductors of a TRRS connector are assigned to different purposes by different manufacturers. Any 3.5 mm plug can be plugged mechanically into any socket, but many combinations are electrically incompatible. For 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. Mono 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, orvice versa.
Two different forms are frequently found. Both place left audio on the tip and right audio on the first ring, same as stereo connectors. They differ in the placement of the microphone and return contacts.
TheOMTP standard places the ground return on the sleeve and the microphone on the second ring.[58] It has been accepted as a national Chinese standard YDT 1885–2009. In the West, it is mostly used on older devices, such as older Nokia mobiles, olderSamsung smartphones, and someSony Ericsson phones.[59] It is widely used in products meant for the Chinese market.[60][61] Headsets using this wiring are sometimes indicated by black plastic separators between the rings.[62][61]
TheCTIA/AHJ standard reverses these contacts, putting the microphone on the sleeve. It is used by Apple'siPhone line until the6S andSE (1st). In the West, these products made it the de facto TRRS standard.[63][64][65] It is now used byHTC devices, recentSamsung,Nokia, andSony phones, among others. It 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. Headsets using this wiring are sometimes indicated by white plastic separators between the rings.[62][61]
If a CTIA headset is connected to an OMTP device, the missing ground effectively connects the speakers in series,out-of-phase. This removes the singer's voice on typical popular music recordings, which place the singers in the center. If the main microphone button is held down, shorting across the microphone and restoring ground, the correct sound may be audible.[61]
| Standard | Tip | Ring 1 | Ring 2 | Sleeve | Devices using this standard |
|---|---|---|---|---|---|
| CTIA,AHJ | Left audio | Right audio | Ground | Microphone | MostAndroid devices.[66]Apple,HTC,LG,BlackBerry, latestNokia (including 1st generation Lumia as well as later models[clarification needed]), latestSamsung,Jolla,Microsoft (includingSurface, andXbox One controller), Sony Playstation 4 (DualShock 4[67]), Google Pixel 4a,Librem 5 |
| CTIA-style AV[68] | Left audio | Right audio | Ground | CVBS video | AppleiPod (up to 6th generation),Raspberry Pi (2014 onwards),Xbox 360 E,Zune (defunct), some older mobile phones (includingNokia N93,Nokia N95,[69]Samsung Galaxy S GT-I9000,[70]T-Mobile Sidekick 4G) |
| OMTP | Left audio | Right audio | Microphone | Ground | Old Nokia and alsoLumia starting from the 2nd generation),[71] old Samsung (2012Chromebooks), some old Sony Ericsson smartphones (2010 and 2011Xperias),[72] Sony (PlayStation Vita),OnePlus One. |
| OMTP-style radios | Speaker | Clone | Microphone / PTT | Ground | Yaesu FT-60Ramateur radio hand-held.[73][74][75] |
| Video/audio 1 | Left audio | CVBS video | Ground | Right audio | Sony and Panasoniccamcorders. On some early Sony camcorders, this socket doubled up as a headphone socket. When a headphone plug was inserted, ring 2 was shorted to the sleeve contact and the camcorder output the right audio on ring 1.[76] |
| Video/audio 2 | CVBS video | Left audio | Right audio | Ground | Unknown camcorders, portable VCD and DVD players, Western Digital TV live!, some newer LG TVs. |
| Video/audio 3 | CVBS video | Left audio | Ground | Right audio | Toshiba TVs |
| Video/audio 4 | Left audio | Right audio | CVBS video | Ground | Grandstream GXV-3500[77] |
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.[78] 3-pole 3.5 mm TRS connectors are defined in JIS C 6560. See also JIS C 5401 and IEC 60130-8.
Apple'siPod Shuffle 2G reuses its TRRS socket not just for audio but also for charging and syncing overUSB when docked.[79]
TheUSB Type-C Cable and Connector Specification specifies a mapping from aUSB-C jack to a 4-pole TRRS jack, for the use of headsets, and supports both CTIA and OMTP (YD/T 1885–2009) modes.[80] Some devices transparently handle many jack standards,[81][82] and there are hardware implementations of this available as components.[83] This is accomplished in some cases by applying a voltage to the sleeve and second ring to detect the wiring. The 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.[84]
A TRRRS standard for 3.5 mm connectors was developed by ITU-T.[85] The standard, called P.382 (formerly P.MMIC), outlines technical requirements and test methods for a 5-conductor socket and plug configuration. Compared 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.
P.382 requires compliant sockets and plugs to be backward compatible with legacy TRRS and TRS connectors. Therefore, P.382-compliant TRRRS connectors should allow for seamless integration when used on new products. 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. It was commonly found onSony phones starting with theXperia Z1,Xperis XZ1 andXperia 1 II.
Another TRRRS standard for 4.4 mm connectors following JEITA RC-8141C was introduced in 2015 and is used forbalanced audio connections, in particular forheadphone cables. This connector is often called aPentaconn connector, following the brand name of Nippon DICS (NDICS). It is used by some Sony products like theM1Z Walkman of their Signature series and by someSennheiser products like theHD 820 headphone or the HDV 820 DAC headphone amplifier.[86][87]
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Panel-mounted jacks may include switch contacts. Most 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. Stereo sockets commonly provide two such NC contacts, one for the tip (left channel) and one for the ring or collar (right channel). Some jacks also have such a connection on the sleeve. As 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. Less commonly, jacks may feature normally open (NO) or change-over contacts or the switch contacts may be isolated from the connector signals.
The original purpose of these contacts was for switching in telephone exchanges, for which there were many patterns. Two sets of change-over contacts, isolated from the connector contacts, were common. The more recent pattern of one NC contact for each signal path, internally attached to the connector contact, stems from their use as headphone jacks. In many amplifiers and equipment containing them, such as electronic organs, a headphone jack is provided that disconnects the loudspeakers when in use. This is done by means of these switch contacts. In other equipment, a dummy load is provided when the headphones are not connected. This is also easily provided by means of these NC contacts.
Other uses for these contacts have been found. One is to interrupt a signal path in a mixing console toinsert an effects processor. 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. A similar arrangement is used in patch panels fornormalization (seePatch panel § Normalization).
Where 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.
To eliminate the need for a separate power switch, a standard stereo jack is used on most battery-powered guitareffects pedals. The internal battery has its negative terminal wired to the sleeve contact of the jack. When 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.
The connector assembly is usually made by one or more hollow and one solid pin. The jack is then assembled with pins separated by aninsulating material.
Connectors that are tarnished, or that were not manufactured within tight tolerances, are prone to cause poor connections.[88] Depending 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).[88]
A great number of jack configurations have been used, including the following, though the simple mono and stereo jack (examples A and B) are most common:[89]
 | A. Two-conductor TS phone connector (without extra switches). 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. |
 | B. Three-conductor TRS phone connector (without extra switches). 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 inA. |
 | C. Three-conductor jack with two isolatedSPDT 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. |
 | D. Three-conductor jack with two normally closed switches connected to the contacts themselves. This is useful forpatch panel normalization. Another common use is as stereo headphone jack that shuts off the default output (speakers) when the connector is plugged in. |
| Pin | Unbalanced mono | Balanced mono in/out (simplex)[90][A][B] | Unbalanced stereo | |
|---|---|---|---|---|
| In/out (simplex) | Insert[94] | |||
| Tip | Signal | Send or return signal | Positive,hot | Left channel |
| Ring | Ground, orno connection | Return or send signal | Negative,cold | Right channel |
| Sleeve | Ground[C] | |||
When a phone connector is used to make abalanced audio connection, the two active conductors are used fordifferential versions of a monaural signal. The ring, used for the right channel in stereo systems, is used instead for the inverting input.
Where space is a premium, TRS connectors offer a more compact alternative toXLR connectors, and so are common in small audiomixing desks.
Another 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. The inverting input on the ring contact gets correctly grounded when it makes contact with the plug body.
When 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. 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.
This problem does not occur with XLR or when usinggauge B[96] 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. This 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. This same tapered shape used in thegauge B plug can be seen also in aviation and military applications on various diameters of jack connector including the PJ-068 and Bantam plugs. The more common straight-sided profile used in domestic and commercial applications and discussed in most of this article is known asgauge A.
Alternatively, some switched audio jacks contain built-in isolated switches that only activate when the plug is fully inserted.[97] This can be used to avoid the insertion issue, for instance by wiring the connectors through adouble pole, double throw switch that activates only upon full insertion. Or 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.
Phone connectors with three conductors are also commonly used as unbalanced audiopatch points (orinsert points, or simplyinserts), with the output on many mixers found on the tip and the input on the ring. This is often expressed astip send, ring return.[c] Older mixers and some outboard gear[d] have unbalanced insert points withring send, tip return.[e]
In many implementations, the switch contact within the panel socket is used to close the circuit betweensend andreturn when the patch point has no plug inserted. Combiningsend andreturn functions via single1⁄4 in TRS connectors halves the space needed for insert jack fields which would otherwise require two jacks, one forsend and one forreturn.[f]
In some three-conductor TRS phone inserts, the concept is extended by using specially designed phone jacks that will accept a mono phone plug partly insertedto the first click and will then connect the tip to the signal path without breaking it. Standard TRS connectors may also be used in this way with varying success.
In some very compact equipment includingmodular synthesizers, 3.5 mm TS phone connectors are used for patch points.
tip ring sleeve 0–1922.
Also called a 3.5 mm or 1/8" connector, it is a plug and socket widely used for analog audio signals in portable devices.
(e.g.) 3.5mm female stereo mini phone jack to 1/4" male Stereo phone plug Adapter
Remember that sound cards use the smaller 1/8-inch mini-phono plug...
1/8-inch stereo mini-phono plug adapter.
3.5 mm Plug/Jack: Also referred to as a 1/8 inch, auxiliary input, mini stereo, and mini phono.
The 3.5mm mini-phono plug connector of the ATC Probe plugs into the 3.5mm mini-phono jack on the pH meter.
...instead of the headphone jack.... There will be a lightning-to-mini phono adapter included as well.
High power 2-conductor speaker jack carries 15A (continuous) audio speaker current levels.
In order to fit the Chinese national conditions, Apple China released Earpods with some changes, specifically for the Chinese market, to make it in line with the Chinese domestic OMTP standard. ... Therefore, iPhone original headsets sold in China are different from Earpods sold in other regions.
