Re: Surge suppressors

[Nigel Orr <nigel.orr@xxxxxxx>]

At 16:03 27/07/99 +0100, you wrote:
>A signal being vulnerable to filtering is not the problem - surely
>anything transmitted across the mains (or other medium) can suffer from
>that.

True, anything except wired connections are _very_ easily disrupted
(whereas wired are just fairly easily disrupted!).  That's why I wouldn't
currently use X10 or RF for anything critical (although I would trust
spread spectrum for fixed use if it were developed a little more, against
all but the most malicious jamming attempt), and why it worries me to see a
post on comp.home.automation today asking about X-10 linked smoke alarms...

>X10 strikes me as intrinsically sound, it's just the protocol is
>seriously under-developed which is quite amazing considering how old it
>is, and how cheap embedded electronics seems to be.

Power Line (PL) control isn't _such_ a bad idea- though CE marking hasn't
helped- too many manufacturers are making up for bad design by slapping a
suppressor across the L&N terminals to stop the noise getting out... at
least in RF other peoples suppressors usually help rather than hinder!  It
certainly doesn't look to have much of a chance for data transfer outside
the domestic environment, if the IEE continue to point out the problems
that presents...

And it could be made more reliable, with some simple error correction (but
not quite as simple as the current system, which I understand sends the
command bits, then the command bits inverted), and an acknowledge from the
remote end.

>I don't really understand why noone in the USA has furthered the
>development of X10 in this area - there must surely be sufficient
>demand...

I would expect that CEBus or CAN, in their PL spec, require some sort of
acknowledgement and/or error correction.  There is definitely the potential
for it, but I'm not sure if it is required for compliance with the
standard.  If it is, I would expect X10 to modify their products to comply
with whichever standard seems to be winning through, and I'm sure that
could be done, without wasting too much bandwidth, without making the
existing items obsolete.

Maybe there isn't demand- there seem to be a lot of happy X10 users out
there, and as long as they can be convinced they have something good, and
that the reliability is adequate, they won't be rushing to spend money on
something slightly better- cf VHS v Betamax...

So those of us who want something more reliable, but still affordable, will
have to wait till the marketeers have found enough early adopters with
money who will pay for the research, or build our own...

Nigel
--
Nigel Orr                  Research Associate   O   ______
Underwater Acoustics Group,              o / o    \_/(
Dept of Electrical and Electronic Engineering     (_   <   _ (
University of Newcastle Upon Tyne             \______/ \(

------------------------------------------------------------------------
GET WHAT YOU DESERVE! A NextCard Platinum VISA: DOUBLE Rewards points,
NO annual fee & rates as low as 9.9% FIXED APR. Apply online today!
http://clickhere.egroups.com/click/606


eGroups.com home: http://www.egroups.com/group/ukha_d
http://www.egroups.com - Simplifying
group communications