X.21 (sometimes referred to as X21) is an interface specification for differential communications introduced in the mid-1970s by the ITU-T . X.21 was first introduced as a means to provide a digital signaling interface for telecommunications between carriers and customers' equipment. This includes specifications for DTE / DCE physical interface elements, alignment of call control characters and error checking , elements of the call control phase for circuit switching services, and test loops.
31-477: When X.21 is used with V.11 , it provides synchronous data transmission at rates from 600 bit/s to 10 Mbit/s. There is also a variant of X.21 that is only used in select legacy applications, “circuit switched X.21”. X.21 normally is found on a 15-pin D-sub connector and is capable of running full-duplex data transmissions. The Signal Element Timing, or clock, is provided by the carrier (the telephone company), and
62-430: A constant multiple, diameters vary geometrically . Any two successive gauges (e.g., A and B ) have diameters whose ratio (dia. B ÷ dia. A ) is 92 39 {\displaystyle {\sqrt[{39}]{92}}} (approximately 1.12293), while for gauges two steps apart (e.g., A , B , and C ), the ratio of the C to A is about 1.12293 ≈ 1.26098. Similarly for gauges n steps apart
93-468: A copper conductor with plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area . Fusing current (melting wire) is estimated based on 25 °C (77 °F) ambient temperature. The table below assumes DC , or AC frequencies equal to or less than 60 Hz, and does not take skin effect into account. "Turns of wire per unit length"
124-408: A cross section of 250 kcmil. A circular mil is the area of a wire one mil in diameter. One million circular mils is the area of a circle with 1,000 mil (1 inch) diameter. An older abbreviation for one thousand circular mils is MCM . AWG can also be used to describe stranded wire. The AWG of a stranded wire represents the sum of the cross-sectional diameter of the individual strands;
155-575: A slash. For example, a 22 AWG 7/30 stranded wire is a 22 AWG wire made from seven strands of 30 AWG wire. As indicated in the Formulas and Rules of Thumb sections above, differences in AWG translate directly into ratios of diameter or area. This property can be employed to easily find the AWG of a stranded bundle by measuring the diameter and count of its strands. (This only applies to bundles with circular strands of identical size.) To find
186-399: A true multi-point communications network, such as with RS-485 , since there can be only one driver on each pair of wires. However, one driver can fan-out to up to ten receivers. RS-422 can interoperate with interfaces designed to MIL-STD-188-114B , but they are not identical. RS-422 uses a nominal 0 to 5- volt signal, while MIL-STD-188-114B uses a signal symmetric about 0 V. However,
217-612: Is a technical standard originated by the Electronic Industries Alliance , first issued in 1975, that specifies electrical characteristics of a digital signaling circuit. It was meant to be the foundation of a suite of standards that would replace the older RS-232C standard with standards that offered much higher speed, better immunity from noise, and longer cable lengths. RS-422 systems can transmit data at rates as high as 10 Mbit/s , or may be sent on cables as long as 1,200 meters (3,900 ft) at lower rates. It
248-493: Is closely related to RS-423 , which uses the same signaling systems but on a different wiring arrangement. RS-422 specifies differential signaling , with every data line paired with a dedicated return line. It is the voltage difference between these two lines that defines the mark and space, rather than, as in RS-232, the difference in voltage between a data line and a local ground. As the ground voltage can differ at either end of
279-592: Is responsible for correct clocking of the data. X.21 was primarily used in Europe and Japan, for example in the Scandinavian DATEX and German Datex-L [ de ] circuit-switched networks during the 1980s. Article based on X.21 at FOLDOC , and X.21 Pinouts , used with permission . This computer networking article is a stub . You can help Misplaced Pages by expanding it . ITU-T V.11 RS-422 , also known as TIA/EIA-422 ,
310-417: Is similar to many other non-metric gauging systems such as British Standard Wire Gauge (SWG). However, AWG is dissimilar to IEC 60228 , the metric wire-size standard used in most parts of the world, based directly on the wire cross-section area (in square millimetres, mm ). The AWG tables are for a single, solid and round conductor. The AWG of a stranded wire is determined by the cross-sectional area of
341-464: Is the reciprocal of the conductor diameter; it is therefore an upper limit for wire wound in the form of a helix (see solenoid ), based on uninsulated wire. In the North American electrical industry, conductors thicker than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm . The next wire size thicker than 4/0 has
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#1732772573577372-558: The Sony 9-pin connection was used, which makes use of a DE-9 connector. This is the de facto industry standard connector for RS-422, which is still found on broadcast equipment today. AWG American Wire Gauge ( AWG ) is a logarithmic stepped standardized wire gauge system used since 1857, predominantly in North America , for the diameters of round, solid, nonferrous, electrically conducting wire . Dimensions of
403-408: The iMac in 1998. RS-422 is a common transport mechanism for RS-232 extenders. These consist of RS-232 ports on either end of an RS-422 connection. Before hard-disk-based playout and editing systems were used, broadcast automation systems and post-production linear editing facilities used RS-422A to remotely control the players/recorders located in the central apparatus room . In most cases,
434-407: The AWG of 7-strand wire with equal strands, subtract 8.4 from the AWG of a strand. Similarly, for 19-strand subtract 12.7, and for 37 subtract 15.6. Measuring strand diameter is often easier and more accurate than attempting to measure bundle diameter and packing ratio. Such measurement can be done with a wire gauge go-no-go tool or with a caliper or micrometer. Alternative ways are commonly used in
465-485: The RS-422 specification only defines one signal path and does not assign any function to it. Any complete cable assembly with connectors should be labeled with the specification that defined the signal function and mechanical layout of the connector, such as RS-449 . One of the most widespread uses of RS-422 was on the early Macintosh computers. This was implemented in a multi-pin connector that had enough pins to support
496-399: The above formulas. For instance, for 0000 AWG or 4/0 AWG, use n = −3 . The sixth power of √ 92 is very close to 2, which leads to the following rules of thumb: Convenient coincidences result in the following rules of thumb for resistances: The table below shows various data including both the resistance of the various wire gauges and the allowable current ( ampacity ) based on
527-681: The cable, this required RS-232 to use signals with voltage magnitudes greater than 5 volts. Moving to dedicated return lines and always defining ground in reference to the sender allows RS-422 to use 0.4 V, allowing it to run at much higher speeds. RS-423 differs primarily in that it has a single return pin instead of one for each data pin. RS-422 is the common short form title of American National Standards Institute (ANSI) standard ANSI/TIA/EIA-422-B Electrical Characteristics of Balanced Voltage Differential Interface Circuits and its international equivalent ITU-T Recommendation T-REC-V.11 , also known as X.27 . These technical standards specify
558-611: The development of standardized wire gauges rationalized selection of wire for a particular purpose. While the AWG is essentially identical to the Brown & Sharpe (B&S) sheet metal gauge, the B&;S gauge was designed for use with sheet metals as its name suggests. These are functionally interchangeable but the use of B&S in relation to wire gauges, rather than sheet metal gauges, is technically improper. Increasing gauge numbers denote logarithmically decreasing wire diameters, which
589-414: The electrical characteristics of the balanced voltage digital interface circuit. RS-422 provides for data transmission, using balanced, or differential, signaling , with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop. In contrast to EIA-485 , RS-422/V.11 does not allow multiple drivers but only multiple receivers. The first version of RS-422
620-464: The electrical industry to specify wire sizes as AWG. AWG is colloquially referred to as gauge and the zeros in thick wire sizes are referred to as aught / ˈ ɔː t / . Wire sized 1 AWG is referred to as "one gauge" or "No. 1" wire; similarly, thinner sizes are pronounced " x gauge" or "No. x " wire, where x is the positive-integer AWG number. Consecutive AWG wire sizes thicker than No. 1 wire are designated by
651-461: The equivalent solid conductor. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG. By definition, 36 AWG is 0.005 inches in diameter, and 0000 AWG is 0.46 inches in diameter. The ratio of these diameters is 1:92, and there are 40 gauge sizes from 36 to 0000, or 39 steps. Because each successive gauge number increases cross sectional area by
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#1732772573577682-714: The figure A.1. This figure is a conservative guide based on empirical data, not a limit imposed by the standard. RS-422 specifies the electrical characteristics of a single balanced signal. The standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications that require a balanced voltage circuit to transmit data. These other standards would define protocols, connectors, pin assignments and functions. Standards such as EIA-530 ( DB-25 connector) and EIA-449 ( DC-37 connector) use RS-422 electrical signals. Some RS-422 devices have 4 screw terminals for pairs of wire, with one pair used for data in each direction. RS-422 cannot implement
713-411: The gaps between strands are not counted. When made with circular strands, these gaps occupy about 25% of the wire area , thus requiring the overall bundle diameter to be about 13% larger than a solid wire of equal gauge. Stranded wires are specified with three numbers, the overall AWG size, the number of strands, and the AWG size of a strand. The number of strands and the AWG of a strand are separated by
744-507: The individual installation. Figure A.1 shows a maximum length of 1,200 meters (3,900 ft), but this is with a termination, and the annex discusses the fact that many applications can tolerate greater timing and amplitude distortion, and that experience has shown that the cable length may be extended to several kilometers. Conservative maximum data rates with 24 AWG UTP ( POTS ) cable are 10 Mbit/s at 12 m (39 ft) to 90 kbit/s at 1,200 m (3,900 ft), as shown in
775-568: The majority of the common RS-232 pins; the first models used a 9-pin D connector , but this was quickly replaced by a mini-DIN -8 connector. The ports could be put into either RS-232 or RS-422 mode, which changes the behavior of some of the pins while turning others on or off completely. These connectors are used to support RS-232 devices like modems , AppleTalk networking, RS-422 printers, and other peripherals. Two such ports were part of early Apple Macintosh series designs until they were replaced, along with ADB ports, by Universal Serial Bus on
806-447: The maximum data rate decreases as cable length increases. Figure A.1 in the annex plotting this stops at 10 Mbit/s . The maximum cable length is not specified in the standard, but guidance is given in its annex. (This annex is not a formal part of the standard, but is included for information purposes only.) Limitations on line length and data rate vary with the parameters of the cable length, balance, and termination, as well as
837-594: The ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322. ASTM B258-02 also dictates that wire diameters should be tabulated with no more than 4 significant figures, with a resolution of no more than 0.0001 inches (0.1 mils) for wires thicker than 44 AWG, and 0.00001 inches (0.01 mils) for wires 45 AWG and thinner. Sizes with multiple zeros are successively thicker than 0 AWG and can be denoted using " number of zeros /0", for example 4/0 AWG for 0000 AWG. For an m /0 AWG wire, use n = −( m − 1) = 1 − m in
868-583: The ratio of the first to last gauges is about 1.12293 . The diameter of an AWG wire is determined according to the following formula: (where n is the AWG size for gauges from 36 to 0, n = −1 for 00, n = −2 for 000, and n = −3 for 0000. See below for rule.) or equivalently: The gauge can be calculated from the diameter using and the cross-section area is The standard ASTM B258-02 (2008), Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors , defines
899-445: The tolerance for common-mode voltage in both specifications allows them to interoperate. Care must be taken with the termination network. RS-423 is a similar specification for unbalanced signaling. When used in relation to communications wiring, RS-422 wiring refers to cable made of 2 sets of twisted pair , often with each pair being shielded, and a ground wire. While a double-pair cable may be practical for many RS-422 applications,
930-492: The wires are given in ASTM standard B 258. The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity . The AWG originated in the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) required more passes through the drawing dies than 0 gauge wire did. Manufacturers of wire formerly had proprietary wire gauge systems;
961-615: Was issued in 1975, with revision A issued in December 1978. Revision B, published in May 1994 was reaffirmed by the Telecommunications Industry Association in 2005. Several key advantages offered by this standard include the differential receiver, a differential driver and data rates as high as 10 megabits per second at 12 meters (40 ft). Since the signal quality degrades with cable length,