> i seem to recall that RS232 transmissions should be done over
> short cables. since there are only -3/+3v levels, is this true.

Essentially, yes.  EIA/TIA-232 is designed for short distances.
(It was upgraded from a recommended standard, i.e. RS-, to a
full EIA/TIA standard over a decade ago.)

In summary, EIA-232-E specifies the transmiter as +5 to +15 or
-5 to -15 volts.  Receiver state is defined when the circuit is
less than -3 volts or more than +3 volts.

EIA-232-E, section 2.1.3 -- "the signal shall be considered in
the marking (binary 1) state" when the circuit's voltage "is more
negative than -3 volts" and "shall be considered in the spacing
(binary 0) state" when "more positive than +3 volts".  The range
between -3 to +3 volts "is defined as the transition region.  The
signal state is undefined when the voltage" is in this range

EIA-232-E, section 2.1.6 -- "open circuit generator voltage shall
not exceed 25 volts in magnitude".  "The generator [transmitter]
with a test load of 3000 to 7000 ohms [required receiver specs],
the potential at the interface point shall not be less than 5
volts nor more than 15 volts in magnitude".


> Since this transfer shall travel from 0.3 M - 200M i may need
> a potent voltage level and a good shielding.
>
> Which do you think is the best way too boost such a signal,

I wouldn't boost it.  I'd use a balanced transmission mechanism
like EIA-422.
                                                Lee Jones

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