Re: Starting a new flood wiring project

["Keith Doxey" <ukha@xxxxxxx>]

Graham,

We are talking about different areas.

You are mainly talking about cables that are dedicated for a
particular FIXED purpose.

I was referring to the proper usage of STRUCTURED WIRING.
Cables that can be used for any purpose.

Agreed you can buy splitters but that then takes the simplicity away
from structured cabling. You also have to be very careful about how
the splitters are wired.

for example
If the 8 wires are split 1-4 into socket 1, 5-8 into socket 2 then
they are truely split, but if all 8 wires go to each socket but
device A uses 1-4 and device B uses 5-8 again no real problem. The
problem comes when you unplug device A to use device C which used 1-
6, if you have a true splitter then device C would just not work, if
it was a doubler, you could damage both B & C.

There is also an increased possibility of crosstalk between different
devices due to the closer proximity of the cable pairs. Within the
shath there may only be 1mm between conductors whereas with separate
cables there is a minimum of 3mm even if the cables are adjacent for
the whole of the run. CAT5's inherrant high noise immunity may well
prevent any problems but why tempt trouble for the sake of a few
quids worth of cable.

Keith



--- In ukha_d@y..., "Graham Howe" <graham@s...> wrote:
> <very timid mode>I think Keith is wrong, see below</very
timid mode>
>
> Graham
> A CAT5 wire has 8 wires, in a couple of places I have two devices
connected
> to a single CAT5 cable each using different wires. Specifically, at
my front
> door I have the door contact (magnetic, 2 wires) and the hall pir
(4 wires)
> both connected to a single CAT5 cable. In the dining room (others
to follow)
> I have embedded an IR receiver inside a PIR. In both cases the
singals from
> the separate devices are split out at node zero through Krone
blocks. In
> fact a computer network only uses 4 wires and phone only 3 so they
can be
> combined too (splitters can be bought off the shelf). Having said
all of
> this, you should not plan your cable laying to be used in this way
as it
> leaves no headroom at all. But for those of us who have done the
cabling and
> will not be allowed to run more, there are ways of sharing and
splitting.
>