I'm having this design problem:

I have a couple of PIC16F84:s that have to communicate with each other.
I'm going to use some kind of asyncronous serial protocol. But when the
PIC:s are about 50 meters from each other, what is the smartest way to
connect them?

Alt I
The simplest way would be to just connect e.g. RB0 on all PIC:s to the
same wire and hop there will not be any kind of interference.

Alt II
Use some kind of transistor to rise the voltage to about 12 V and a diod
and a zener to level the signal back to 5 V. I tried to illustrate this
in a fast drawn schematic.
http://www.abo.fi/~adoktar/alt2.gif

Alt III
Some kind of bi-directional buffer. Which part would be suitable?

Thanks for your answers, regards,
Andreas Doktar

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