This section describes the various RS-xxx (more properly TIA-xxx) standards and some of the V.xx standards from our good friends at the ITU (did we really say that - they are the guys who still charge for specs!).
A partial apology: The ITU, bless their hearts, now have a policy that you can get two docs for free when you sign up. It's a start but why don't they do like the IEEE 802 guys. Free but only after 6 months. If you are desperate you pay, if not you wait.
Note: Until February 11th, 2011 these specs referenced a EIA/TIA number (sometimes even a TIA/EIA number). EIA is no more. TIA has taken over its functions (for the Telecomms sector). Thus all specs should reference TIA, for example, TIA-232 etc.. Since this is the third change in recent memory (RS -> EIA/TIA -> TIA) it is probably bettor to stick with the RS terminology. Technically it is incorrect but it is stable!
EIA/TIA defines Complete and Electrical standards.
Complete standards may define the electrical characteristics or they may call up one or more Electrical standards. They always define a connector since they are supposed to be complete.
|RS 232||RS-232||E||DB25||Unbalanced point-to-point serial interface on a DB25 connector. Max. official data rate 20Kbps (really).|
|-||DB37||Balanced multi-drop serial interface on a DB37 connector. Max data rate 2Mbps. Not quite the biggest connector in the world - that goes to the old ITU V.35 connector but... Sensible people use 530-A instead.|
|A||DB25||Covers Balanced (RS-422 and RS-485), multi-drop (RS-485) and unbalanced (RS-423) serial interface on a DB25 connector. Max data rate 2.1Mbps.|
|RS 561||RS-562||-||RJ45 (MJ8)||Unbalanced point-to-point serial interface on a RJ45 (Modular Connector 8 positions). Max. data rate 38.4Kbps.|
|RS 574||RS-232||-||DB9||Unbalanced point-to-point serial interface on a DB9 connector. Max. data rate 20Kbps (really).|
|RS 613||RS-612||-||?||Balanced point-to-multipoint serial interface on a ? connector. Max data rate 52Mbps.|
These are Electrical standards and are not Complete that is, they do not define signal names. They are typically referenced in a complete standard. Table below highlight the major characteristics.
|RS-232||+- 3V||+- 25V||300||3K - 7K||Unbalanced point-to-point.|
|RS-562||+- 3V||+- 25V||300||3K - 7K||Unbalanced point-to-point.|
|RS-422-B||+- 7V||+- 12V||100||4K||Multi-drop balanced driver and receiver. Max. of 1200 meters all terminals, max of 500 meters between any two terminals.|
|RS-423-B||+- 7V||-||-||-||Multi-drop unbalanced driver and balanced receiver|
|RS-485||+- 7V||+- 12V||-||-||Multi-point balanced driver and receiver. Max of 1200 meters all terminals, max of 500 meters between any two terminals. Up to 32 stations/terminals assuming 12K load. Lower load allows more terminals.|
|RS-612||-0.5V||+2V||-||-||Balanced driver and receiver. Max differential <= 1.5V.|
The ITU, the 500 pound gorilla of the standards world (and the guys who still charge for specs).
|V.24||V.28||Defines the signal names used in serial interfaces. Connector defined in ISO 2110 and ISO 4902. Practically the same as RS-232|
|V.28||-||unbalanced point-to-point serial interface. Practically the same as RS-232.|
|V.35||-||Term still widely used but standard withdrawn years ago and replaced with V.10 and V.11. Still holds the record for the biggest serial connector known to mankind - the infamous CCITT 37 pin connector. Mostly uses a DB25 connector today but not every manufacturer uses the same wiring standard.|
|V.10||-||unbalanced driver and balanced receiver point-to-point serial interface (a.k.a RS-423-B).|
|V.11||-||Balanced driver and receiver point-to-point serial interface (a.k.a. RS-422-B).|
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