Re: Powerline modem

From: Peter (peterwn_at_parazzdise.net.nz)
Date: 02/10/05 

Date: Thu, 10 Feb 2005 09:48:44 GMT

On Wed, 09 Feb 2005 15:34:38 -0500, James Knott
<james.knott@rogers.com> wrote:

>Joerg wrote:
>
>> In Germany they send around control signals to turn on "night storage
>> heaters". Basically a huge block of bricks that is heated up off-peak
>> and then a fan kicks out the stored heat during the day.
>
>When I was a kid, we had a flat rate electric water heater. It could be
>turned off by the power company, during periods of high demand, using a
>power line carrier system. The power companies also used the power lines
>to carry low speed data. However, neither of those systems required
>anywhere near the bandwidth of BPL, nor were they likely to cause
>interference.
>

Note however that these systems use signalling frequencies of 200 Hz
to 1500Hz and are 'one way'. Bandwidth and other constraints limited
capacity originally to 12 to 25 on / off channels. Injection may be
at zone substations (signal passes through one transformer) or at grid
exit points (signal passes through two transformers). These would be
electronic system nowadays, older ones used three phase alternators to
generate the signal ane electromechanical receivers (eg reed relay to
respond to signal and motor driven cam for selection).

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