:On 17-Jul-99 Matthew Dillon wrote:
:>
:> Obviously you don't get square waves going down the wire - But it is
:> still a digital communications protocol.
:>
:> -Matt
:
:However the physical layer, i.e. the cable, is analogue and the discussion was
:about cables. To carry your reasoning a bit further - a digital
:cellular phone system is not an RF/Wireless system because the data is digital.
:I hope we agree that it is!
:
:Duncan
Duncan, the entire physical world is an analog medium. Well, not
including quantum mechanical effects anyway. Even the photons running
down *FIBER* are essentially analog signals - because the lasers cannot
be turned on and off instantly.
The difference between treating the medium as analog or digital is that
when you treat it as digital you quantize it well above the noise floor
and treat errors seriously - the idea is to recover the data exactly as
it was sent.
When you treat the medium as analog, you either do not quantize it at all,
or you quantize it close to the noise floor and ignore the errors. The
recovered data does not have to exactly match what was sent.
-Matt
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