>
> I am imaging two diodes in parallel, and one of them inverted, like a
>transmision gate, and where is signal, then that way is the one
>transmitting...ummm...i don't know if someone understand what i am
>triying to say, but i am getting things clear...

The two diode trick is cute.

Assume two units, "left" and "right", with the diodes in the middle:

Left----------+-->|--+------------Right
              |      |
              +--|<--+


When LEFT sends +5V to RIGHT, the current flows left to right, and the top diode that points left to right conducts, and you get +0.3V on the left side, relative to the right.
When RIGHT sends, you get +0.3V on the right side, relative to the left.

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