Please Mr Andy, don't think I ran away after asking my questions,
It is just not as easy as you could imagine for me to be often connected.
Yours replies are very helped, I understand as Mr Kai explained in his second threat when he said with voltage driving we could use only one line to drive many outputs.
I'm going to read to carefully read the link Mr Kai gave to have a look at the use of currents signal before before asking any else questions. Thanks for all Sirs.