{{Short description|Standard for serial communication}} {{Infobox fieldbus protocol |name = RS423 | standard = EIA RS-423 |governing_body = |website = |type_of_network = |physical_media = Group of copper cables |network_topology = Point-to-point, Multi-dropped |maximum_devices = 10 (1 driver & 10 receivers) |maximum_distance = 1200 meters (4000 feet) |maximum_speed = |device_addressing = |mode_of_operation = Single-ended (unbalanced) |maximum_baud_rate =Up to 100kbit/s |voltage = -6V to +6V (maximum) |mark1=-4V to -6V |space0=+4V to +6V |available_signals=Tx, Rx, GND |connector_types = Not specified }}

'''RS-423''', also known as '''TIA/EIA-423''', is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. RS-423 systems can transmit data on cables as long as {{Convert|1200|m|sp=us}}.{{dubious|Maximum length|date=September 2021}} Although it was originally intended as a successor to RS-232C offering greater cable lengths, it is not widely used.<ref>{{cite web |title=EIA-423 |url=http://foldoc.org/rs-423|publisher=foldoc.org|access-date=2021-07-08}}</ref>

RS-423 specifies an unbalanced (single-ended) interface, similar to RS-232, with a single, unidirectional sending driver, and allowing for up to 10 receivers.<ref>Buchanan W.J. (2004) RS-422, RS-423 and RS-485. In: ''The Handbook of Data Communications and Networks.'' Springer, Boston, MA.{{ISBN|978-1-4757-1067-0}} page 627</ref> It is normally implemented in integrated circuit technology and can also be employed for the interchange of serial binary signals between DTE & DCE. It is related to RS-422, which uses similar voltage levels but operates with differential signaling.

==Standard scope== RS-423 is the common short form title of American National Standards Institute (ANSI) standard ''ANSI/TIA/EIA-423-B Electrical Characteristics of Unbalanced Voltage Digital Interface Circuits'' and its international equivalent ''ITU-T Recommendation T-REC-V.10'',<ref>{{cite web |title=V.10 : Electrical characteristics for unbalanced double-current interchange circuits operating at data signalling rates nominally up to 100&nbsp;kbit/s |url=https://www.itu.int/rec/T-REC-V.10/en%20V.10%20ITU%20Recommendation%20T-REC-V.10|website=itu.int |access-date=3 May 2023}}</ref> also known as ''X.26''. These technical standards specify the electrical characteristics of the unbalanced voltage digital interface circuit.<ref name="definition">''TIA/EIA STANDARD, Electrical Characteristics of Unbalanced Voltage Digital Interface Circuits, TIA/EIA-423-B'', May 1993</ref> RS-423 provides for data transmission, using unbalanced or single-ended signals, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.

== Characteristics == thumb|Guidelines for data rate versus line length RS-423 is related to the RS-422 standard, but uses single-ended signaling referenced to a common ground instead of the differential signaling used by RS-422. Use of a common ground is one weakness of RS-423 (and RS-232): if devices are far enough apart or on separate power systems, the ground will degrade between them and communications will fail, resulting in a condition that is difficult to trace.<ref>[http://www.ti.com/lit/an/snla044b/snla044b.pdf National Semiconductor Application Note AN-1031 "TIA/EIA-422-B Overview", January 2000, National Semiconductor Inc.] page 2 - evaluate the combination of cable length and data rate.</ref>

RS-423 specifies the electrical characteristics of a single unbalanced signal. The standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications which require a unbalanced voltage circuit to transmit data.{{citation needed|date=May 2023}}

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-423 electrical signals.{{citation needed|date=May 2023}}

== Applications == The BBC Micro computer uses RS-423 with a 5-pin DIN connector. DEC used it extensively with a Modified Modular Jack connector. This was sometimes called "DEC-423".{{citation needed|date=May 2023}}

==See also== * List of network buses * Fieldbus * Profibus

==References== {{Reflist}}

==Further reading== {{Wikibooks|Serial Programming/RS-423}} * [http://pinouts.ru/SerialPorts/rs-423_pinout.shtml RS-423 specification] * [http://www.zprod.org/PG/machines/bbcMicroInterface.htm Diagram of pin connections for BBC micro]

{{Computer-bus}}

{{DEFAULTSORT:Rs-423}} Category:Serial buses Category:EIA standards