At 11:41 11/6/97 -0700, you wrote:
>The less than simple answer is that RS-485 has a much better common mode
>rejection ratio.  If one observes the same signal in both transmission
>wires, the error can be corrected very easily.
>>The simple answer is that the noise cancels out.
>>>I would like to ask, why with using balanced line(rs485) data can be
>>>transmitted longer than using unbalanced line(rs232)?

Another simple answer,,, and maby a bit more to the point, the 50 foot
limit on rs232 is from the fcc,,, nothing to do with data tranmission, just
rf noise.  I've seen good cable rs232 links run well over a thousand feet
in the "old days".



'Grif' N7IVS