390:
505:
where even RS-423, which was functionally similar to RS-232, no longer fit in a DB25 connector. This led to the use of the larger DC-37, but even that did not have enough pins to support RS-422, so this was "solved" by adding the additional ground wires to a separate DE-9 connector. This resulted in a "horrendous number of wires" and the conclusion in 1983 that its "success... remains to be seen."
687:
475:
During the late 1970s, the EIA began developing two new serial data standards to replace RS-232. RS-232 had a number of issues that limited its performance and practicality. Among these was the relatively large voltages used for signalling, +5 and -5V for mark and space. To supply these, a +12V power
488:
The reason for the large voltages was due to ground voltages. RS-232 included both a protective ground and a signal ground in the standard, but did not define how these were to be implemented. It was often the case that the protective ground was left unconnected, and the signal ground was connected
500:
standards used well-defined grounding that was always based on the sender's reference, and made the signal only 400 mV above or below this reference. In the case of RS-422, for instance, every signal had a second pin operating at the opposite voltage, thereby balancing the voltages and always
504:
The primary difference between RS-422 and RS-423 was that the former had a return line for every signal, while the later had a single shared signal ground. This meant that RS-422 had double the number of signal wires. Along with other changes, the number of connections began to grow, to the point
489:
to ground at both ends. As a result, if there was a slight difference in ground potential at the two ends of the cable, the voltage in the signal ground pin might not be zero, and large signal voltages were needed to provide a positive signal in this case.
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implementations. These high voltages and unbalanced communications also resulted in relatively short cable lengths, nominally set to a maximum of 50 feet (15 m), although in practice they could be somewhat longer if running at slower speeds.
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providing a positive signal. When this process was starting, the decision was made to unbundle the mechanical aspects of the standard from the electrical, with the former becoming the RS-449 standards track.
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connector if the 422 protocol was used. The resulting cable mess was already dismissed as hopeless before the standard was even finalized. The effort was eventually abandoned in favor of
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EIA-449 General
Purpose 37-Position and 9-Position Interface for Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange
136:
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The standard was rarely used, although it could be found on some network communication equipment. EIA-449-1 was rescinded in
January 1986 and superseded by
567:, expansion devices were located on an external port, so the power supply had to feed both 5 and 12V to the machine, and then pass the 12V out though the
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set in, the number of required pins began to grow beyond what a DB-25 could handle, and the RS-449 effort started to define a new connector.
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96:
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November 1977, reprinted in
Telebyte Technology "Data Communication Library" Greenlawn NY, 1985, no ISBN, no Library of Congress card number
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supply was typically required, which made it somewhat difficult to implement in a market that was rapidly being dominated by +5/0V
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512:, the final version EIA-449-1 was withdrawn in September 2002. The most widespread use of RS-422/423, the early
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computers, used a simple 9-pin DIN connector and for inter-machine links used only three-wire connectors.
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The need for 12V to drive RS-232 often led to some complexity in early computer
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connectors. This was initially split into two closely related efforts,
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455:449 emerged as an unwieldy system using a large
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8:
674:. Vol. 8, no. 2. pp. 146–178.
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480:(TTL) circuitry and even lower-voltage
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432:449 was part of an effort to replace
7:
425:. The full title of the standard is
703:RS-449 interface pinout and signals
25:
668:"Welcome to the Standards Jungle"
656:Electronic Industries Association
492:To address this problem, the new
685:
459:connector along with a separate
526:Electronic Industries Alliance
1:
666:Witten, Ian (February 1983).
415:data communications equipment
401:specification, also known as
413:, typically a computer, and
478:transistor-transistor logic
744:
628:"TIA Standards Documents"
723:Physical layer protocols
563:. For instance, in the
411:data terminal equipment
31:Internet protocol suite
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692:RS-422-423 449 pinout
565:Atari 8-bit computers
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694:at Wikimedia Commons
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698:EIA/TIA Standards
690:Media related to
541:Apple Desktop Bus
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38:Application layer
16:(Redirected from
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660:EIA Standard 449
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630:. Archived from
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203:Transport layer
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680:External links
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728:EIA standards
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634:on 2008-02-16
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450:feature creep
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393:RS-449 pinout
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718:Serial buses
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636:. Retrieved
632:the original
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615:Witten 1983
600:Witten 1983
712:Categories
638:2008-01-19
579:References
571:connector.
471:Background
320:Link layer
584:Citations
520:See also
650:Sources
434:RS-232C
407:TIA-449
403:EIA-449
350:more...
334:Tunnels
310:more...
243:more...
193:more...
182:TLS/SSL
137:ONC/RPC
74: (
18:EIA-449
531:RS-485
498:RS-423
494:RS-422
465:RS-530
446:RS-423
442:RS-422
399:RS-449
177:Telnet
76:HTTP/3
547:Notes
457:DC-37
448:. As
438:DB-25
419:modem
304:IPsec
82:HTTPS
672:Byte
496:and
482:CMOS
461:DE-9
444:and
397:The
299:IGMP
279:ICMP
237:QUIC
232:RSVP
227:SCTP
222:DCCP
187:XMPP
167:SNMP
162:SMTP
147:RTSP
122:OSPF
112:NNTP
107:MQTT
102:MGCP
97:LDAP
87:IMAP
72:HTTP
52:DHCP
569:SIO
536:USB
421:or
405:or
344:MAC
339:PPP
329:ARP
294:ECN
289:NDP
217:UDP
212:TCP
172:SSH
157:SIP
152:RIP
142:RTP
132:PTP
127:POP
117:NTP
92:IRC
67:FTP
62:DNS
47:BGP
714::
670:.
658:,
607:^
592:^
429:.
283:v6
272:v6
267:v4
262:IP
56:v6
641:.
378:e
371:t
364:v
285:)
281:(
78:)
58:)
54:(
20:)
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