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A jack plug (. MODERN JACK PLUGS Modern jack plugs are available in three standard sizes. The original 6.35 mm or 1/4" 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 '''subminiature''' sizes were originally designed as two-conductor connectors for earpieces on Transistor Radio s. The 3.5 mm and 2.5 mm sizes are also referred to as 1/8" and 3/32" respectively in the United States. All three sizes are now readily available in two-conductor (mono) and three-conductor ( Stereo or Tip Ring Sleeve ) 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 Camcorder s, providing stereo sound plus a video signal. This interface is also seen on some Laptop Computer s. Proprietary interfaces using both four and five conductor versions exist, notably the audio connector on the IPod MP3 player, where the extra conductors are used to supply power for accessories. 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 3.5mm jack. Sockets exist that can make either an optical connection to such a plug or an electrical connection to a stereo jack. Both two-conductor and three-conductor versions of the three standard sizes are readily available in Male (plug) and Female (socket or simply "jack") line 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 line 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, which was 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 about 15 Ampere s for the 1/4" version. Non-standard 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. Several obsolete versions of the 1/4" jack plug exist, including:
MONO AND STEREO COMPATIBILITY 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 Microphone s, Electric Guitar s, Headphones 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 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:
USES Some common uses of jack plugs and their matching jacks are:
SWITCH CONTACTS 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 though this is less useful as that contact is usually ground. 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, thus forming a patch point. See Tip Ring Sleeve . 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 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. On some DI Unit s and guitar Effects Unit s, a normally open switch contact on one of the signal connectors is used to connect an internal battery whenever a cord is connected. The desired effect is to switch the unit off whenever the cord is removed. A side effect is to discharge the battery if it is not removed, for example if equipment is left connected overnight. If it is desired to activate the switch contacts without actually inserting a plug in a 1/4 inch jack socket, a rod of the construction toy Knex can be used. However care should be taken to use a rod long enough that it can be pulled back out. 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. 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 Switch es. 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. SEE ALSO |
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