Editing RS-232 (section)

=={{anchor|A|B|C|D|E|F}}History==
RS-232 was first introduced in 1960<ref name="CAM_1974"/> by the [[Electronic Industries Association]] (EIA) as a ''Recommended Standard''.<ref>{{cite web |title=RS232 Tutorial on Data Interface and cables |url=http://www.arcelect.com/rs232.htm|publisher=ARC Electronics |access-date=2011-07-28 |year=2010}}</ref><ref name="Metering_Glossary">[http://www.landisgyr.eu/en/pub/services_support/metering_glossary.cfm?eventGlossary=glossary.Search&initial=E Metering Glossary] {{webarchive|url=https://web.archive.org/web/20121129015220/http://www.landisgyr.eu/en/pub/services_support/metering_glossary.cfm?eventGlossary=glossary.Search&initial=E |date=2012-11-29 }} Landis + Gyr Tutorial (see ''EIA'')</ref> The original DTEs were electromechanical [[teletypewriter]]s, and the original DCEs were (usually) modems. When [[electronic terminal]]s (smart and dumb) began to be used, they were often designed to be interchangeable with teletypewriters, and so supported RS-232.

Because the standard did not foresee the requirements of devices such as computers, printers, test instruments, [[POS terminal]]s, and so on, designers implementing an RS-232 compatible interface on their equipment often interpreted the standard idiosyncratically. The resulting common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. The lack of adherence to the standards produced a thriving industry of [[breakout box]]es, patch boxes, test equipment, books, and other aids for the connection of disparate equipment. A common deviation from the standard was to drive the signals at a reduced voltage. Some manufacturers therefore built transmitters that supplied +5&nbsp;V and −5&nbsp;V and labeled them as "RS-232 compatible".{{Citation needed|date=April 2011}}

Later personal computers (and other devices) started to make use of the standard so that they could connect to existing equipment. For many years, an RS-232-compatible port was a standard feature for [[serial communication]]s, such as modem connections, on many computers (with the computer acting as the DTE). It remained in widespread use into the late 1990s. In personal computer peripherals, it has largely been supplanted by other interface standards, such as USB. RS-232 is still used to connect older designs of peripherals, industrial equipment (such as [[programmable logic controller|PLC]]s), [[system console|console]] ports, and special purpose equipment.

The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and, most recently as TIA 232. The standard continued to be revised and updated by the [[Electronic Industries Association]] and since 1988 by the [[Telecommunications Industry Association]] (TIA).<ref>{{cite web |title=TIA Facts at a Glance |url=http://www.tiaonline.org/about/ |work=About TIA |publisher=[[Telecommunications Industry Association]] |access-date=2011-07-28}}</ref> Revision C was issued in a document dated August 1969. Revision D was issued in 1986. The current revision is ''TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange'', issued in 1997. Changes since Revision C have been in timing and details intended to improve harmonization with the [[CCITT]] standard {{ill|ITU-T V.24{{!}}ITU-T/CCITT V.24|de|V.24}}, but equipment built to the current standard will interoperate with older versions.{{Citation needed|date=April 2011}}

Related [[ITU-T]] standards include V.24 (circuit identification) and {{ill|ITU-T V.28{{!}}ITU-T/CCITT V.28|de|V.28}} (signal voltage and timing characteristics).{{Citation needed|date=April 2011}}

In revision D of EIA-232, the D-subminiature connector was formally included as part of the standard (it was only referenced in the appendix of RS-232-C). The voltage range was extended to ±25&nbsp;volts, and the circuit capacitance limit was expressly stated as 2500&nbsp;pF. Revision E of EIA-232 introduced a new, smaller, standard D-shell 26-pin "Alt A" connector, and made other changes to improve compatibility with CCITT standards V.24, V.28 and ISO 2110.<ref>S. Mackay, E. Wright, D. Reynders, J. Park, ''Practical Industrial Data Networks: Design, Installation, and Troubleshooting'', Newnes, 2004 {{ISBN|07506 5807X}}, pages 41-42</ref>

Specification document revision history:
*EIA RS-232 (May 1960) "Interface Between Data Terminal Equipment & Data"<ref name="CAM_1974"/>
*EIA RS-232-A (October 1963)<ref name="CAM_1974"/>
*EIA RS-232-B (October 1965)<ref name="CAM_1974"/>
*EIA RS-232-C (August 1969) "Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange"<ref name="CAM_1974">{{citation |title=Standards for Computer Aided Manufacturing |author-first1=John M. |author-last1=Evans, Jr. |author-first2=Joseph T. |author-last2=O'Neill |author-first3=John L. |author-last3=Little |author-first4=James S. |author-last4=Albus |author-first5=Anthony J. |author-last5=Barbera |author-first6=Dennis W. |author-last6=Fife |author-first7=Elizabeth N. |author-last7=Fong |author-first8=David E. |author-last8=Gilsinn |author-first9=Frances E. |author-last9=Holberton |author-first10=Brian G. |author-last10=Lucas |author-first11=Gordon E. |author-last11=Lyon |author-first12=Beatrice A. S. |author-last12=Marron |author-first13=Albercht J. |author-last13=Neumann |author-first14=Mabel V. |author-last14=Vickers |author-first15=Justin C. |author-last15=Walker |location=Office of Developmental Automation and Control Technology, Institute for Computer Sciences and Technology, National Bureau of Standards, Washington, DC, USA |edition=Second Interim Report |date=October 1976 |publisher=Manufacturing Technology Division, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio 45433 |id=NBSIR 76-1094 |url=https://archive.org/stream/standardsforcom7610evan_0/standardsforcom7610evan_0_djvu.txt |access-date=2017-03-04}}</ref>
*EIA EIA-232-D (1986)
*TIA TIA/EIA-232-E (1991) "Interface Between Data Terminal Equipment and Data Communications Equipment Employing Serial Binary Data Interchange"
*TIA TIA/EIA-232-F (October 1997<!-- 1997-10-01 -->)
*ANSI/TIA-232-F-1997 (R2002)
*TIA TIA-232-F (R2012)