Hi Frans:

1. Balanced lines (with RS422/485 differential drivers and receivers)
rejects common mode noise. That's why TV, radio and recording studios
use balanced lines for all routings for high quality sound (mostly
reducing AC 60 Hz and florescent light hum).

2. RS422/485 line impedance is usually used with 50 or 120 ohms
termination, lower than RS232's 1 K unterminated - so signal reflections
are much less. This gives higher bandwidth to a given cable and allows
longer signal lines (until the wire's series resistance gets large
compared to the termination).

3. RS422/485 outputs are lower voltage swing, slew-rate controlled,
which helps crosstalk and reflections.

See this URL for more details:
 http://www.maxim-ic.com/AppNotes.htm

-Wayne
> ----------
> From:         Frans Gunawan[SMTP:f@POBOXES.COM]
> Sent:         Thursday, November 06, 1997 3:02 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [OT}balanced line
>
> I would like to ask, why with using balanced line(rs485) data can be
> transmitted longer than using unbalanced line(rs232)?
> I can't find good explanation about this. if possible, detail
> please...
> thanks
> www.poboxes.com/f
> f
>