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TRS connector

"Triple contact plug" as described in 1907.
The ring and sleeve are transposed in relation to modern usage.

A TRS connector (tip, ring, sleeve) also called an audio jack, phone plug, jack plug, stereo plug, mini-jack, mini-stereo, or headphone jack, is a common audio connector. It is cylindrical in shape, typically with three contacts, although sometimes with two (a TS connector) or four (a TRRS connector).

It was invented for use in telephone switchboards in the 19th century and is still widely used, both in its original ¼″ (6.3 mm) size and in miniaturized versions ⅛″ (3.5 mm) and 3/32″ (2.5 mm). The connector's name is an initialism derived from the names of three conducting parts of the plug: Tip, Ring, and Sleeve – hence, TRS.

In the UK, the terms jack plug and jack socket are commonly used for the respectively male and female TRS connectors.

In the U.S., a stationary (more fixed) connector is called a jack. The terms phone plug and phone jack are sometimes used to refer to TRS connectors, but are also sometimes used colloquially to refer to RJ11 and older telephone plugs and the corresponding jacks that connect wired telephones to wall outlets. (The similar terms phono plug and phono jack refer to RCA connectors though both plug types are used in tandem when a computer or MP3 player connects to a stereo.) In conversation, the diameter is often added to specify which size: quarter-inch phone plug or 3.5 mm phone jack for the unbalanced two-channel three-contact version, and balanced TRS jack or TRS phone plug for the balanced one-channel three-contact version.

Modern connectors

2.5 mm mono (TS), 3.5 mm mono and stereo (TRS), and 1/4″ (6.35 mm) stereo (TRS) jack plugs
Modern TS and TRS connectors are available in three standard sizes. The original 1/4″ (6.35 mm) version dates from 1878, for use in manual telephone exchanges—making it possibly the oldest electrical connector standard still in use. The 3.5 mm or miniature and 2.5 mm or sub-miniature sizes were originally designed as two-conductor connectors for earpieces on transistor radios. The 3.5 mm and 2.5 mm sizes are also referred to as ⅛″ and 3/32″ respectively in the United States, though those dimensions are only approximations. All three sizes are now readily available in two-conductor (unbalanced mono) and three-conductor (balanced mono or unbalanced stereo) versions.

Four and five conductor versions of the 3.5 mm plug are used for certain applications. A four conductor version is becoming a de facto standard output connector for compact camcorders, providing stereo sound plus a video signal. This interface is also seen on some laptop computers and on the second-generation iPod Shuffle. Proprietary interfaces using both four and five conductor versions exist, where the extra conductors were used to supply power for accessories. The four conductor 3.5 mm plug is also used as a speaker-microphone connector on handheld amateur radio transceivers from Yaesu. There is also an optical connector used for TOSLINK (mainly on things like portable equipment; hi-fi separates and similar tend to use the standard square connector) that is the same size as a 3.5 mm jack. Sockets exist that can make either an optical connection to such a plug or an electrical connection to a stereo jack plug. These combination electrical/optical output jacks are present on all Apple Macbook, Macbook Pro and Intel iMac computers.

A three- or four-conductor version of the 2.5 mm plug is widely used on cell phone handsfree headsets, providing mono (three conductor) or stereo (four conductor) sound and a microphone input. Common stereo headphones with the 2.5 mm plug are often not compatible with this type of socket. A 3.5 mm version of this plug is now commonly available on mobile telephones as well. A 3.5 mm stereo-plus-mic plug is available that is compatible with standard 3.5 mm stereo headphones.

Although relatively unknown in modern consumer electronics, the professional audio world and the telecommunication industry has used tiny telephone (TT) connectors in patch bays which are mid-size phone plugs with a 4.4 mm (0.173-inch) diameter shaft. In the telecom world, this is known as a "bantam" plug. Though unable to handle as much power as a 6.35 mm (0.25-inch) jack, and not as reliable, TTs have been used for professional console and outboard patchbays in studios and live sound applications, in which a single patch panel requires hundreds of patch points in a limited space. The TRS versions of TT connectors are capable of handling balanced line signals and have been employed in pro audio installations. Recently, all-in-one digital audio switching matrixes and digital signal processors have reduced the need for physical patching and extensive patch bays.

Both two-conductor and three-conductor versions of the three standard sizes are readily available in male and female inline versions, and panel-mounting female versions. Panel-mounting male versions of these also exist but are rare, as they are vulnerable to mechanical damage and therefore unreliable. Female inline versions are also notoriously unreliable and are avoided by many users.

The most common arrangement remains to have the male plug on the cable and the female socket mounted in a piece of equipment: the original intention of the design. 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 15 amperes for certain heavy duty 1/4″ versions.

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 .210 inch inside diameter jacks for fire safety communication jacks in public buildings, the same size found in vintage 16 mm projector speaker jacks.

A dual 310 patch cable, two-pin jack plug

  • A two-pin version, known to the telecom industry as a "310 connector" consists of two TRS 6.35 mm jack plugs at a centre spacing of .625 inches. The socket versions of these can be used with normal jack plugs provided the plug bodies are not too large, but the plug version will only mate with two jack sockets at .625 inches centre spacing, or with line sockets, again with sufficiently small bodies. These connectors are still widely used today in telephone company central offices on "DSX" patch panels for DS1 circuits. A similar type of 3.5 mm connector is often used in the armrests of older aircraft, as part of the on-board entertainment system. Plugging a stereo plug into one of the two mono jacks typically results in the audio coming into only one ear. Adaptors are available.
  • A short-barrelled version also exists, once used on high-impedance mono headphones, and in particular those used in World War II aircraft. 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. These are still manufactured but are now regarded as a non-standard size.

Mono and stereo compatibility

Modern profile 2-conductor male 1/4″ TRS connectors.

In the original application in manual telephone exchanges, many different configurations of 1/4″ jack plug 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 with microphones, electric guitars, headphones, loudspeakers, and many other items of audio equipment.

When a three-conductor version of the 1/4″ jack was introduced for use with stereo headphones, it was given a sharper tip profile in order to make it possible to manufacture jacks (sockets) that would accept only stereo plugs, to avoid short-circuiting the right channel amplifier. This attempt has long been abandoned, and now the normal convention is that all plugs fit all sockets of the same size, regardless of whether they are balanced mono, unbalanced mono or stereo. Most 1/4″ plugs, mono or stereo, now have the profile of the original stereo plug, although a few rounded mono plugs are also still produced. The profiles of stereo miniature and subminiature plugs have always been identical to the mono plugs of the same size.

The results of this physical compatibility are:
  • If a two-conductor plug of the same size is connected to a three-conductor socket, the result is that the ring (right channel) of the socket is grounded. This property is deliberately used in several applications, see "tip ring sleeve", below. However, grounding one channel may also be dangerous to the equipment if the result is to short circuit the output of the right channel amplifier. In any case, any signal from the right channel is naturally lost.
  • If a three-conductor plug is connected to a two-conductor socket, normally the result is to leave the ring of the plug unconnected (open circuit). In the days of vacuum tubes this was also potentially dangerous to equipment but most solid state devices tolerate this condition well. A 3-conductor socket could be wired as an unbalanced mono socket to ground the ring in this situation, but the more conventional wiring is to leave the ring unconnected, exactly simulating a mono socket.


Some common uses of jack plugs and their matching sockets are:

  • Headphone and earphone jacks on a wide range of equipment. 1/4″ plugs are common on home and professional component equipment, while 3.5 mm plugs are nearly universal for portable audio equipment. 2.5 mm plugs are not as common, but are used on communication equipment such as cordless phones, mobile phones, and two-way radios.
  • Consumer electronics devices such as digital cameras, camcorders, and portable DVD players use 3.5 mm connectors for composite video and audio output. Typically, a TRS connection is used for mono audio plus video, and a TRRS connection for stereo audio plus video. Cables designed for this use are often terminated with RCA connectors on the other end.
  • Microphone inputs on tape and cassette recorders, sometimes with remote control switching on the ring.
  • Patching points (insert points) on a wide range of equipment.
  • Personal computers, sometimes using a sound card plugged into the computer. Stereo 3.5 mm jacks are used for:
    • Line in (stereo)
    • Line out (stereo)
    • Headphones/loudspeaker out (stereo)
    • Microphone input (mono, usually with 5 volt power available on the ring. Note that traditional, incompatible, use of a stereo plug for a mono microphone is for balanced output)
    • Laptop computers generally have one line level jack for headphones and one mono jack for a microphone at microphone level. You can use an attenuating cable to convert line level or use a signal from an XLR connector, but it is not designed to record from a stereo device such as a radio or music player.
    • LCD monitors with built-in speakers will require a 3.5 mm male-male cable from the sound card.
Note: Higher end sound cards sometimes sport a breakout panel which supports 1/4″ plug devices as well.
    • Devices designed for surround output may use multiple jacks for paired channels (ex. TRS for front left and right; TRRS for front center, rear center, and subwoofer; and TRS for surround left and right). Circuitry on the sound device may be used to switch between traditional Line In/Line Out/Mic functions and surround output.
  • Electric guitars. Almost all electric guitars use a 1/4″ mono jack (socket) as their output connector. Some makes (such as Shergold) use a stereo jack instead for stereo output, or a second stereo jack, in addition to a mono jack (as with Rickenbacker).
  • Instrument amplifiers for guitars, basses and similar amplified musical instruments. 1/4″ jacks are overwhelmingly the most common connectors for:
    • Inputs. A shielded cable with a mono 1/4″ jack plug on each end is commonly called a guitar cord or a patching cord, the first name reflecting this usage, the second the history of the jack plug's development for use in manual telephone exchanges.
    • Loudspeaker outputs, especially on low-end equipment. Speakon connectors are generally considered superior and so are usually preferred on higher-end equipment, although it is not uncommon to find both provided for compatibility. Heavy-duty 1/4″ loudspeaker jacks are rated at 15A maximum which limits them to applications involving less than 1,800 watts. 1/4″ loudspeaker jacks commonly aren't rigged to lock the plug in place and will short out the amplifier's output circuitry if connected or disconnected when the amplifier is live.
    • Line outputs.
    • Foot switches and effects pedals. Stereo plugs are used for double switches (for example by Fender). There is little compatibility between makers.
    • Effects loops, which are normally wired as patch points.
  • Electronic keyboards use jacks for a similar range of uses to guitars and amplifiers, and in addition
    • Sustain pedals.
    • Expression pedals.
  • Electronic drums use jacks to connect sensor pads to the synthesizer module or MIDI encoder. In this usage, a change in voltage on the wire indicates a drum stroke.
  • Some compact and/or economy model audio mixing desks use stereo jacks for balanced microphone inputs.
  • The majority of professional audio equipment uses mono jacks as the standard unbalanced input or output connector, often providing a 1/4″ unbalanced line connector alongside (or in a few cases in the middle of!) and as an alternative to an XLR balanced line connector.
  • Modular synthesizers commonly use monophonic cables for creating patches.
  • ¼ in connectors are widely used to connect external processing devices to mixing consoles' insert points (see Insert ). TRS or TS connectors might be used in pairs as separate Send and Return jacks or a single TRS jack might be employed for both Send and Return in which case the signals are unbalanced. The single unbalanced combination Send/Return TRS insert jack saves both panel space and component complexity. Note that mixing console insert points can also be XLR, RCA or Bantam TT (tiny telephone) jacks, depending on the make and model.
  • Some small electronic devices such as audio cassette players, especially in the cheaper price brackets, use a two-conductor 3.5 mm or 2.5 mm jack as a DC power connector.
  • Some photographic studio strobe lights have 1/4″ or 3.5 mm jacks for the flash synchronization input. A camera's electrical flash output (PC socket or hot shoe adapter) is cabled to the strobe light's sync input jacks. Some examples: Calumet Travelite, and Speedotron use a 1/4″ mono jack as the sync input; White Lightning uses 1/4″ stereo jacks; Pocket Wizard (radio trigger) and Alien Bees use 3.5 mm mono jacks.
  • Some cameras (for example, Canon, Sigma, and Pentax DSLRs) use the 2.5 mm stereo jack for the connector for the remote shutter release (and focus activation); examples are Canon's RS-60E3 remote switch and Sigma's CR-21 wired remote control.
  • Some miniaturized electronic devices use 2.5 mm or 3.5 mm jack plugs as serial port connectors for data transfer and unit programming. This technique is particularly common on graphing calculators, such as the TI-83 series, and some types of amateur and two-way radio, though in some more modern equipment USB mini-B connectors are provided in addition to or instead of jack connectors. The second-generation iPod Shuffle from Apple has a single TRS jack which serves as headphone, USB, or power supply, depending on the connected plug.
  • On CCTV cameras and video encoders, mono audio in (originating from a microphone in or near the camera) and mono audio out (destined to a speaker in or near the camera) are provided on a single three-conductor connector, where one signal is on the tip conductor and the other is on the ring conductor.
  • The Atari 2600 (Video Computer System), the first widely popular home video game console with interchangeable software programs, used a 3.5 mm TS (two conductor) jack for 9V(?) DC power.

Switch contacts

A jack plug breaks the contact of a normally closed switch.
Miniature jack plugs and jacks.
All are 3.5 mm except the gold-plated plug, which is 2.5 mm.
All the jacks are two-conductor (TS).
The tan-colored jacks have a normally-closed switch.

Panel-mounting jacks are often provided with switch contacts. Most commonly, a mono jack is provided with a single 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 live) and one for the ring or collar (right channel live). Some designs of jack 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 socket was in use.

Less commonly, some jacks are provided with normally open (NO) or change-over contacts, and/or the switch contacts may be isolated from the connector.

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 to enable other circuitry to be inserted. This is done by using one NC contact of a stereo jack to connect the tip and ring together when no plug is inserted. The tip is then made the output, and the ring the input (or vice versa), thus forming a patch point.

Another use is to provide alternative mono or stereo output facilities on some guitars and electronic organs. This is achieved by using two mono jacks, one for left channel and one for right, and wiring the NC contact on the right channel jack to the tip of the other, to connect the two connector tips together when the right channel output is not in use. This then mixes the signals so that the left channel jack doubles as a mono output.

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.

A three-conductor signal input socket is used on some battery-powered guitar effects pedals to eliminate the need for a separate power switch. When the user plugs in a two-conductor guitar or microphone lead, the resulting short-circuit between earth 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. A side effect is the risk of inadvertently discharging the battery if the lead is not removed after use, for example if equipment is left connected overnight.

Tip/ring/sleeve terminology

[[Image:Jack plug.png|right|thumb|300px|1. Sleeve: usually ground

2. Ring: Right-hand channel for stereo signals, negative phase for balanced mono signals, power supply for power-requiring mono signal sources

3. Tip: Left-hand channel for stereo signals, positive phase for balanced mono signals, signal line for unbalanced mono signals

4. Insulating rings]]In twisted pair wiring to this day, the non-inverting and/or "live" (or "hot") wire of each pair is known as the ring, while the inverting and/or "earthy" (or "neutral") wire is known as the tip, inherited from the traditional connection via the TRS connector in telephone systems. If the pair is shielded, or if the pair is accompanied by a dedicated earth wire, this third conductor is known as the sleeve. This usage corresponds to the connection to a three-connector jack plug in a manual telephone exchange. This appears to have originated with the use of TRS jacks by switchboard operators with the tip and ring wires attached to the corresponding parts of the jack. Originally, the hot and ground were reversed, but often the metallic desktops of the switch boards were scarred by the discharge from the tips and the system was reversed to the present usage.

The term tip ring sleeve is more common in some English-speaking countries than others. Outside of the USA the term stereo jack plug is probably more common, even for connectors not used for stereo. The modern profile three-conductor jack plug was originally designed for stereo signal connections, with left channel on the tip, right on the ring and common return on the body or sleeve. The term TRS is particularly appropriate to distinguish these three-conductor (stereo) plugs used in other than stereo applications.

Unbalanced Output Unbalanced Input Unbalanced Insert Balanced Stereo
Tip Signal Signal Send or Return signal Positive/"Hot" Left channel
Ring Ground or No Connection Ground or No Connection Return or Send signal Negative/"Cold" Right channel
Sleeve Ground Ground Ground Ground Ground

Note that the first version of the popular Mackie 1604 mixer, the CR1604, used a Tip Negative, Ring Positive jack wiring scheme on the main left and right outputs.

Note that early QSC amplifiers used a tip negative, ring positive input jack wiring scheme.

:Whirlwind Line Balancer/Splitters do not use the Sleeve as a conductor on their unbalanced ¼ in TRS input. Tip and Ring are wired to the transformer's two terminals; Sleeve is not connected.



When a TRS is used to make a balanced connection, the two active conductors are both used for a monaural signal. The ring, used for the right channel in stereo systems, is used instead for the inverting input. This is a common use in small audio mixing desks, where space is a premium and they offer a more compact alternative to XLR connectors. Another advantage offered by TRS connectors used for balanced microphone inputs is that a standard unbalanced signal lead using a mono jack plug can simply be plugged into such an input. The ring (right channel) contact then makes contact with the plug body, correctly grounding the inverting input.

The disadvantage of using TRS jacks for balanced audio connections is that the ground mates last and the socket grounds the plug tip and ring when inserting or pulling out the plug. 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. Professional audio equipment uses XLR connectors which mate the ground signal on pin 1 first.

TRS connectors are also commonly used as unbalanced audio patch points (or insert points, or simply inserts), with the output on many mixers found on the tip (left channel) and the input on the ring (right channel). This is often expressed as "tip send, ring return." Other mixers have unbalanced insert points with "ring send, tip return." One advantage of this system is that the switch contact within the panel socket, originally designed for other purposes, can be used to close the circuit when the patch point is not in use. An advantage of the "tip send" patch point is that if it is used as an output only, a 2-conductor mono jack plug correctly grounds the input. In the same fashion, use of a "tip return" insert style allows a mono jack plug to bring an unbalanced signal directly into the circuit, though in this case the output must be robust enough to withstand being grounded. Combining Send and Return functions via single 1/4″ TRS connectors in this way is seen in very many professional and semi-professional audio mixing desks, due to the halving of space needed for insert jack fields which would otherwise require two jacks, one for Send and one for Return. The tradeoff is that unbalanced signals are more prone to buzz, hum and outside interference.

In some TRS inserts, the concept is extended by using specially designed TRS jacks that will accept a mono jack plug partly inserted "to the first click" and will then connect the tip to the signal path without breaking it. Most standard TRS jacks can also be used in this way with varying success, but neither the switch contact nor the tip contact can be relied upon unless the internal contacts have been designed with extra strength for holding the plug tip in place. Even with stronger contacts, an accidental mechanical movement of the inserted plug can interrupt signal within the circuit. For maximum reliability, any usage involving "first click" or "half-click" positions will instead rewire the plug to short Tip and Ring together and then insert this modified plug all the way into the jack.

The TRS Tip Return, Ring Send unbalanced insert configuration is mostly found on older mixers. This allowed for the insert jack to serve as a standard-wired mono line input that would bypass the mic preamp (and likely a resistive pad, as well as other circuitry, depending on the design), and thus improve sound quality. However tip send has become the generally accepted standard for mixer inserts since the early-to-mid 1990s. The TRS Ring Send configuration is still found on some compressor sidechain input jacks such as the dbx 166XL.

In some very compact equipment, 3.5 mm TRS jacks are used as patch points.

Some sound recording devices use a TRS as a mono microphone input, using the tip as the signal path and the ring to connect a standby switch on the microphone.

Computer sound

Personal computer sound cards from Creative Labs, Sound Blaster or compatible to these use a 1/8″ TRS as a mono microphone input, and deliver a 5 V polarising voltage on the ring to power electret microphones from the card manufacturer. Sometimes called phantom power, this is not a suitable power source for microphones designed for true phantom power and is better called bias voltage. (Note that this is not a polarizing voltage for the condenser, as electrets by definition have an intrinsic voltage; it is power for a preamplifier FET [transistor] built into the electret microphone can.) Compatibility between different manufacturers is unreliable.

Normally, 1/8″ 3-conductor sockets are used in computer soundcards for stereo output. Thus, for a soundcard with 5.1 output, there will be 3 sockets to accommodate 6 channels—front left & right, surround left & right, and center & subwoofer. But the 6.1 and 7.1 channel soundcards from Creative Labs are equipped with 1 and 2 sockets of 1/8″ 4-conductor sockets respectively. This is to accommodate rear-center (6.1) or rear left & right (7.1) channels without additional sockets on the sound card. But speaker have normal 3-conductor sockets. In Creative's documentation, the word "pole" is used instead of "conductor".

The Applemarker PlainTalk microphone jack used on some older Macintosh systems is designed to accept an extended 1/8″ TRS; in this case, the tip carries power for a preamplifier inside the microphone. If a PlainTalk-compatible microphone is not available, the jack can accept a line-level sound input, though it cannot accept a standard microphone without a preamp.

Generally, all of Apple's computers now have combination electric/optical 1/8″ TRS jacks for both input and output. This allows for conventional stereo input and output with electrical connections, or 5.1 digital input and output with a mini-Toslink cable.

Plug-in power( from: )

Recording equipment

Stereo devices which use "plug-in power": the electret capsules are wired in this way

Many small video cameras, laptops, Minidisc recorders and other consumer devices use a 3.5 mm microphone connector for attaching a (mono/stereo) microphone to the system.These fall into three categories:
  • Devices (usually of the "toy" variety), which use an un-powered microphone: usually a cheap dynamic or piezo microphone. The microphone generates its own voltage, and does not require power.
  • Devices (usually very expensive recorders, for hi-fi or broadcast use) which use a self-powered microphone: usually an expensive dynamic microphone with internal battery-powered amplifier.
  • Devices (most consumer equipment) which use a "plug-in powered" microphone: an electret microphone containing an internal FET amplifier. These provide a good quality signal, in a very small microphone. However, the internal FET requires a DC power supply, which is provided as a bias voltage for an internal preamp transistor.

Plug-in power is supplied on the same line as the audio signal, using an RC filter. The DC bias voltage supplies the FET amplifier (at a low current), while the capacitor decouples the DC supply from the AC input to the recorder. Typically, V=1.5 V, R=1 kΩ, C=47 µF.

If a recorder provides plug-in power, and the microphone does not need it, everything will usually work ok, although the sound quality may be lower than expected. In the converse case (recorder provides no power; microphone requires power), no sound will be recorded. Neither misconfiguration will damageconsumer hardware, but it could destroy a broadcast-type microphone.

Aircraft headsets

Aviation plug type U-174/U or Nexus TP120, commonly used on military aircraft and civil helicopters.
Commercial and general aviation civil airplane headset plugs are similar, but with a difference. A standard 1/4″ monaural plug, type PJ-055, is used for headphones, paired with special tip-ring-sleeve, 0.206 inch diameter plug, type PJ-068, for the microphone. The extra connection in the microphone plug is used by an optional push-to-talk switch.

Military aircraft and civil helicopters have another type known by the designation U-174/U. They are also known as Nexus TP120 telephone plugs. They are similar to a standard 1/4″ (6.3 mm) stereo plug, but with a 7.1 mm (0.281") diameter short shaft with an extra sleeve. This provides four connections in one plug, allowing for a pair of monaural headphones, a microphone, a push-to-talk switch and a common ground conductor.

Some mobile phones such as the Nokia N95, the Apple iPhone and the HP IPAQ 500 Voice Messenger also use a similarly-wired plug for their headset.

Configurations and schematic symbols

These examples are meant to illustrate each possible component of such jacks, but many other configurations using these basic components are available. All examples in the above figure are oriented so the plug 'enters' from the right.

A. A simple two-conductor jack. 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. A three-conductor, or TRS, jack. The upper connector is the tip, as it is farther away from the sleeve. The sleeve is shown connected directly to the chassis, a very common configuration. This is the typical configuration for a balanced connection. Some jacks have metal mounting connections (which would make this connection) and some have plastic, to isolate the sleeve from the chassis, and provide a separate sleeve connection point, as in A.

C. This three-conductor jack has two isolated SPDT switches. They are 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 would be useful for a device that turns on when a plug is inserted, and off otherwise, with the power routed through the switches.

D. This three-conductor jack has two normally closed switches connected to the contacts themselves. This would be useful for a patch point, for instance, or for allowing another signal to feed the line until a plug is inserted. The switches open when a plug is inserted. A common use for this style of connector is a stereo headphone jack that shuts off the default output (speakers) when the connector is plugged in.

Color Codes

These codes were standardized by Microsoft and Intelmarker in 1999 for computers as part of the PC99 standard. See: PCxx Standards.
green TRS 1/8″ stereo output, front channels or headphones
black TRS 1/8″ stereo output, rear channels
grey TRS 1/8″ stereo output, side channels
gold TRS 1/8″ dual output, center and subwoofer
blue TRS 1/8″ stereo input, line level
pink TRS 1/8″ mono or stereo microphone input

See also


  1. Gibson, Bill. (2007) The Ultimate Live Sound Operator's Handbook, p. 202. Hal Leonard Corporation. ISBN 1423419715
  2., page 137

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