RE: Re: Starting a new flood wiring project

["Graham Howe" <graham@xxxxxxx>]

None of my CAT5 cables are 'fixed' purpose, they all terminate in standard
RJ45 ports. What I am saying is that I have in a couple of places, put two
devices on one piece of CAT5 that is then terminated with an RJ45 plug and
can be stuck into any socket. It is true to say that this has so far
involved items that tend to be in a fixed location, but part of the logic
of
plugging such items in is to enable them to be relocated if necessary (e.g.
false triggers on a PIR or removal of an alarm system due to house move).

Graham

> -----Original Message-----
> From: Keith Doxey [mailto:ukha@xxxxxxx]
> Sent: 12 October 2001 14:42
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: Starting a new flood wiring project
>
>
> 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.
> >
>
>
>
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