> > > There is no law that the lower voltage on the bus should be 0V: I 
> > > can imagine a but with for instance signalling levels 9V and 12V.
> > 
> > Works for downstream only. You have some power to get rid of at the 
> > sender, though.
> 
> Hmm... such a system would nessesitate some sort of voltage 
> regulator at the slaves, unless the voltages were 5V and, say, 3V

You will always need a form of regulation at the slavess, unless you can
ensure that the voltage loss in the wires and the voltage drop due to
depletion of local charge storage (the local elco's) does no harm. So I
would go for a voltage that permits local regulators. If the '0' voltage
is still enough for the local regulators you won't have to worry about
big storage capacitors in each slave. But this all depends on current
consumption, number of lasves, length and type of wire, etc.

> So what would the node need to detect a HF signal? High-pass 
> filter w/ a capacitor?

PLL? Or an IR diode + TSOP receiever?

> > > 100 nodes might be too large for some setups, maybe split in 
> > > separate strings, or add repeaters.
> 
> Note that for installation reasons, the nodes really should 
> be in a star configuration, by strings do you mean strings of nodes?

Ooh, you should have said so! And what are the other parameters? (wire
length, wire resistance, current consumption, slave oparting voltage,
cost/reliability balance, etc)

>Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
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