1 ⁄ 4 inch) two-contact phone plug used for various signals including loudspeaker, A 6.35 mm (inch) two-contact phone plug used for various signals including electric guitar microphone and line-level audio. Similarly, two-, four- and five- contact versions are called TS, TRRS and TRRRS connectors respectively.
The original 1⁄4 inch (6.35 mm) version descends from as early as 1877, when the first-ever telephone switchboard was installed at 109 Court Street in Boston in a building owned by Charles Williams, Jr.;[8][9] or 1878, when an early switchboard was used for the first commercial manual telephone exchange[10][11] in New Haven, Connecticut created by George W. In February 1884, C. E. Scribner was issued US Patent 293,198[14] for a “jack-knife” connector that is the origin of calling the receptacle a “jack”.
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) 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 or miniature size was originally designed in the 1950s as two-conductor connectors for earpieces on transistor radios, and remains a standard still used today. [23] This roughly half-sized version of the original, popularized by the Sony EFM-117J radio (released in 1964),[24][25][failed verification] is still commonly used in portable applications. The three-conductor version became very popular with its application on the Walkman in 1979, as unlike earlier transistor radios, these devices had no speaker of their own; the usual way to listen to them was to plug in headphones.
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. A four-conductor version is often used in compact camcorders and portable media players, providing stereo sound and composite analog video. It is also used for a combination of stereo audio, a microphone, and controlling media playback, calls, volume and/or a virtual assistant on some laptop computers and most mobile phones,[27] and some handheld amateur radio transceivers from Yaesu.
Professional audio and the telecommunication industry use a 0.173 in (4.4 mm) diameter plug, associated with trademarked names including Bantam, TT, Tini-Telephone, and Tini-Tel. [31] The three-conductor TRS versions are capable of handling balanced line signals and are used in professional audio installations. Though unable to handle as much power, and less reliable than a 6.35 mm (0.250 in) jack,[32] Bantam connectors are used for professional console and outboard patchbays in recording studio and live sound applications, where large numbers of patch points are needed in a limited space.
A two-pin version, known to the telecom industry as a “310 connector”, consists of two 1⁄4-inch phone plugs at a centre spacing of 5⁄8 inch (16 mm).
These connectors are still 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 in-flight entertainment system. A short-barrelled version of the phone plug was used for 20th century high-impedance mono headphones, and in particular those used in World War II aircraft. Commercial and general aviation (GA) civil airplane headset plugs are similar, but not identical.
Aviation headphones are paired with special tip-ring-sleeve, 3/16-in (0.206 in)/5.23-mm diameter plug,[citation needed] type PJ-068 (PL-68), for the microphone.
The extra (tip) connection in the microphone plug is often left unconnected but is also sometimes used for various functions, most commonly an optional push-to-talk switch, but on some aircraft it carries headphone audio and on others a DC supply. Aviation plug type U-174/U or Nexus TP120, commonly used on military aircraft and civil helicopters Of these many varieties, only the two-conductor version with a rounded tip profile was compatible between different manufacturers, and this was the design that was at first adopted for use with microphones, electric guitars, headphones, loudspeakers, and other audio equipment.
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 in order 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. 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. 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.
Personal computer sound cards, such as Creative Labs’ Sound Blaster line, use a 3.5 mm phone connector as a mono microphone input, and deliver a 5 V voltage on the ring to power electret microphones. Normally, 3.5 mm three-conductor sockets are used in computer sound cards for stereo output.
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. Neither misconfiguration will damage consumer hardware, but providing power when none is needed could destroy a broadcast-type microphone.
All iPhone models from the first generation to the 6S and SE use a four-conductor (TRRS) phone connector (center) for a wired headset. Three- or four-conductor (TRS or TRRS) 2.5 mm and 3.5 mm sockets are common on older cell phones and newer smartphones respectively, providing mono (three conductor) or stereo (four conductor) sound and a microphone input, together with signaling (e.g., push a button to answer a call). The second, which reverses these contacts, with the microphone on the sleeve, is used by Apple’s iPhone line, and has become the de facto TRRS standard, to maintain compatibility with these products. This is referred to as CTIA/AHJ, and has the disadvantage that the mic will be shorted to ground if the body of the device is metal and the sleeve has a flange that contacts it.
If a CTIA headset is connected to a mobile phone with OMTP interface, the missing ground will effectively connect speakers in out-of-phase series, resulting in no voice on typical popular music recordings where the singers are in the center; in this case, if the main microphone button is held down, shorting across the microphone and restoring ground, the correct sound may be audible. 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. Some devices transparently handle many jack standards,[60][61] and there are hardware implementations of this available as components.
Compared to the legacy TRRS standard, TRRRS provides one extra line that can be used for connecting a second microphone or external power to/from the audio accessory. P.382 requires compliant sockets and plugs to be backwards compatible with legacy TRRS and TRS connectors. TRRRS connectors enable following audio applications: active noise cancelling, binaural recording and others, where dual analogue microphone lines can be directly connected to a host device.
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 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. 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 standard stereo jack is used on most battery-powered guitar effects pedals to eliminate the need for a separate power switch.
In this configuration, the internal battery has its negative terminal wired to the sleeve contact of the jack. When the user plugs in a two-conductor (mono) guitar or microphone lead, the resulting short circuit between 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. A drawback of this design is the risk of inadvertently discharging the battery if the lead is not removed after use, such as if the equipment is left plugged in overnight. 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 most common circuit configurations are the simple mono and stereo jacks (A and B); however there are a great number of variants manufactured. Notes 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. Early QSC amplifiers used a tip negative, ring positive input wiring scheme. When a phone connector is used to make a balanced connection, the two active conductors are both used for a monaural signal.
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.
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 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 (bridged) are not interrupted by the insertion or removal of connectors. XLR connectors used in much professional audio equipment mate the ground signal on pin 1 first.
Phone connectors with three conductors 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). 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 phone plug correctly grounds the input. In the same fashion, use of a “tip return” insert style allows a mono phone 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 in TRS connectors in this way is seen in very many professional and semi-professional audio mixing desks, because it halves the space needed for insert jack fields which would otherwise need two jacks, one for send and one for return. Even with stronger contacts, an accidental mechanical movement of the inserted plug can interrupt signal within the circuit.
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. The TRS ring send configuration is still found on some compressor sidechain input jacks such as the dbx 166XL. ^ [33] 0.210 inch inside diameter jacks are also found in discontinued Bell & Howell 16 mm projector speakers. ^ Some higher-end sound cards provide a breakout panel that supports 1 ⁄ 4 in plug devices as well. ^ The traditional use of a stereo plug for a mono microphone for balanced output is incompatible with this configuration.
^ An attenuating cable can convert line level or use a signal from an XLR connector , but is not designed to record from a stereo device such as a radio or music player. ^ Circuitry on the sound device may be used to switch between traditional Line In/Line Out/Mic functions and surround output.
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