> > Soon my electronic gate will be ready witch is
> > About 120 feet far from my desk and I need to
> > Build bidirectional communication with whole
> > House there are doors and switches I need to know
> > The status of it. My favorite interface is I2C but the problem
> > Is that I2C is not good for 120 feet distance I guess my
> > Choice is RS485 differential phase but what I do not know is
> > By using 4 wires 2 for receive and 2 for transmit can I
communicate
> > with all 35 sensors ?. So RS485 works like RS232 I do not see any
way
> > of sharing from same bus I need to make communication like I2C but
> > for 120 feet long any help will highly appreciated.

There's an online RS485 article at...

http://www.circuitcellar.com/library/ccofeature/perrin0799/index.asp

Tim

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