Re: Nigel's gratuitous troll

["Keith Doxey" <keith.doxey@xxxxxxx>]

Hi Raymond,

First of all....why I am not in favour of Radio/Powerline comms

When the first cordless telephone appeared many moons ago there was no
security coding on them and very few people had problems with them because
they were expensive and there werent many around. As they grew in
popularity
so did the problems,

people using other peoples base stations to make calls. -  cured by
security
coding
difficulty getting a clear channel - temporarily cured by adding more
channels

Then came digital and the interference mostly went away, but they still
arent in everyones houses. When they are there will be congestion problems
again at certain times. Consider what it is like trying to use a mobile
phone on the motorway immeadiately after a big pile up has occured, no
connection because everyone is trying to use the network at the same time
and there isnt the bandwidth available.

With your DECT phone you only use it for a small percentage of the day. The
chances of you and all your neighbours within interfering range all wanting
to use them at the same time is probably nil. However, when you start
talking about using RF for linking your Hifi and TV throughout the house
and
having all sorts of appliances constantly chatting amongst themselves then
the airwaves get pretty full. As the prices drop and your neighbours start
to buy these goodies as well I thing it will get pretty hectic.

Collision detection avoids problems with data corruption but they are still
a bad thing, firstly you sent the data and got an acknowledgement that it
was bad data so you resend and it is confirmed good data. End result...data
gets through but it took twice as long as it should have, it doubled the
traffic on the network and more traffic means greater risk of collisions.
(just like the roads !!!)

With cable it would almost certainly have got through first time.
Powerline technology like X10 also suffers similar problems but without
error checking and acknowledgement the problems are much worse. We in the
UK
also have a greater risk of interference from adjacent properties. Our
houses are much smaller and much closer together than in the US. Also the
Americans only seem to have 2 houses fed from a mains transformer, here a
single substation can feed several streets.

Taking your point about not plugging things in twice, if that were the
case,
everyone would still have a radiogram in the corner of the lounge so they
only had to plug the mains in. Loads of things have more than one lead, you
already mentioned the TV, lots of them are portables that allegedly dont
need an aerial but most people plug one in because the RF reception on it
is
crap due to reflections from people moving in the room. Video, Satellite,
Hifi many phones and answering machines, computers all have more than one
lead to plug in.

USB does indeed combine 2 data wires and 2 power wires in the one
cable/plug
but only for very low power devices. Big stuff still requires its own power
supply, and by daisy chaining the USB lead are you not plugging it in more
than once?

At work I am installing CCTV cameras using my Video over CAT 5 boxes
(yes...the first "production run" does now exist) and these use a
single
CAT5 for the power and video (+ audio if required). They are plugged into
our structured wiring and can be moved wherever we want them almost
instantly. For checking camera positions we were plugging into different
sockets and patching them to a TV where we could see the image. It is dead
easy to move stuff anywhere.

Lots of people have to rewire older homes and those fortunate enough to
have
custom built home all have the opportunity to install CAT5 with the minimum
of effort. As long as you have CAT5 adjacent to every mains socket you can
have anything anywhere.

Thats what I am doing but I appreciate others do feel differently.

Keith

Keith Doxey
http://www.btinternet.com/~krazy.keith
Krazy Keith's World of DIY HomeAutomation


> -----Original Message-----
> From: Raymond [mailto:Reb.barnett@xxxxxxx]
> Sent: 01 September 1999 17:26
> To: 'ukha_d@xxxxxxx'
> Subject: [ukha_d] Re: Nigel's gratuitous troll
>
> I'm not really articulating myself properly, but my basic point is
that
> for domestic home automation, you are never going to sell a system to
> ordinary people that needs a re-wire of their house and everything
> plugged in twice. I'm sure the ideal would be to use a 4-pin plug to
> transmit your data down, but I can't see that happening for a long
> while. And if you don't sell the system to ordinary people, then
volumes
> will always be low, and we'll moan about high prices in the UK.
>
> Radio transmissions do seem to be fairly well regulated, so I don't
see
> why a standard for DECT like transmissions of audio and control
> information isn't possible within a domestic environment. If the
> transmissions via radio are digital and have proper collision
detection
> etc then I don't see what the problem is.
>
> I accept that cabled protocols will always be better in principal, but
> then I also accept that Betamax was better in principal...
>


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