At 11:05 AM -0800 1/7/00, David Linker wrote:
>My recollection is that in addition, RS-232 specifies 12V, while RS-422
>specifies 5V, although virtually all hardware will work with the lower
>voltage.

The big difference (that everyone else has missed) is that RS-232 specifies
a pinout and at least first order functions for those pins.  RS-422 *only*
specifies voltage levels, and I think pulse shaping, leaving it to RS-449
or some other standard to specify pinout and function.

RS-232 specifies +/- 3-25 Volts as the output so both 5 and 12 are OK.  On
input nominally you would just look at which way you were from zero volts,
though most implementations used a +1.5V threshold or so to avoid input
noise on unconnected or grounded lines.  I'm pretty sure RS-422 is similar,
except the signals are differential.  As someone noted you can take the
right half of a RS-422 output and it becomes RS-423, which is compatible
with RS-232 voltage levels.

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