RE: HA without fallback-CBUS

["Ian Lowe" <ianlowe@xxxxxxxxxxxxxxxxx>]

> I've also heard that coax would be better than twisted-pairs, the
separation & the
> dielectric being the thing and the twisting just a way of keeping the
pairs
> together - but using coax would be too expensive.   Am I right in all
this
?

Not really.

We used to use co-ax for networks, the old BNC connectors and 10-Base2
cabling that ran machine to machine in a long bus rather than the more
modern hub to device cabling.

There are situations where Coaxial cables are the best, but that tends to
be
for carrying very high frequency signals, which is not always the same as
high bandwidth. Think of it in terms of radios (because, basically, that's
what they are!) - if you have a single tuner then you can listen to a
single
station - a fixed amount of audio information. If you tune to a higher
frequency, you can get another channel but still the same amount of
information. Move to a completely different range of frequencies and you
can
pick up TV - again a single channel, but more information.

Now, instead, picture that you have thirty or so tuners, all tuned to
different stations - you can now receive a whole lot more audio information
at once, at the same frequency as before by using more of the available
bandwidth. That's more what Gigabit Ethernet (and ADSL for that matter) do
-
they have lots of receivers on a chip, making use of much more of the
available cable.

Co-ax is really good for a single high frequency signal, like your cable-tv
box, but twisted pair is much better for handling digital signals (square
waves essentially behave like an infinite number of sine waves going down
the same cable at once)

Those twists are not just to hold the cable together, far from it. Within
each pair, one wire (normally the coloured one) is the signal wire, and the
other (the colour + white one) is a ground wire. When a signal is sent down
these wires, the signal wire gets the raw output, and the ground wire gets
the opposite of the signal (so, if the signal is a "1", the
ground wire gets
a "0" and so on).

This makes it dramatically better at carrying signals in a
"noisy"
environment (like your house) - the signal wire and ground wire are tied
very closely together, so they get exposed to the same noise along the
path,
and the receiver can easily get the signal back at the other end.

All of the pairs in the cable have a slightly different twist rate, to give
even more protection - it helps stop the signals from bleeding between
pairs
(called "cross talk")

Incidentally, this is the source of the biggest "gotcha" in home
cabling
(and a distressing number of businesses too) If someone wires the CAT5 into
an RJ45 plug as "white colour white colour white colour white
colour", you
get a strange bug - computers can transmit but not receive - they get a
link
light, but no data back. To make matters worse *some* PCs and network cards
will work okay, and some won't.

The reason - the first two cables are okay - that puts the Transmit + and -
on a single pair, but the receive + and - (pins 3 and 6) end up on
different
pairs, which means that the signal is badly deteriorated. If it works (and
usually gigabit cards will work well at 100Mb speeds) it will be slow and
unreliable.

> at the moment, it seems cables are running ahead of the equipment
being
connected, at least > when it comes to Giga-Ethernet - but for how long,
I
wonder - will the move to HD TV & DVD
> change the situation, at least in multi-channel distribution
situations ?

I wouldn't worry about multi-channel distribution on HD. It's highly
unlikely to be even possible, given the DRM paranoia that the studios are
building in right at the lowest level.

Given that HDCP is all about a secure signal path, the chance of having two
outputs active on a player at once is pretty much nil, and conventional
splitters won't work. That's the thing about HD and it's DRM B.S. - it's
going to prevent hobbyists like us from doing what we want to do (like pipe
AV around the house, watch the movie that's playing "big screen"
on the
projector on the wee LCD telly in the kitchen at the same time as well
etc.)

Watch for the "WARNING" page on HD DVDs - I'd bet the dug's
kidney that they
will start to have "illegal if played on non-approved hardware"
messages
soon. Remember what Vivendi's CFO said about DRM - "Pay per view is
coming,
get used to it."

I.