At 01:01 PM 11/27/97 +1000, you wrote:
>There has been some discussion about sending data via a powerline.  National
>Semiconductor make the LM1893/LM2893 Carrier-Current Transceiver. . . .
>
>Sounds pretty good to me.  Maybe someone  has had experience with this IC.
  I
>would like to use it to transmitt digitised temperature data 250 metres
across
>a farm.

        i have some experience using this chip, and it works pretty well.
i used an external driver and was able to get 9600 baud all over a house
(though it's really not spec'd for that.)  some problems:

-my application (multiple channel dimming) generated quite a lot of
conducted EMI.  this has to be carefully filtered if the link is going to
work at high speeds.

-it won't work across multiple legs of a transformer unless you
specifically couple it.  in your standard 220/110V house, that means if you
plug it into an outlet, only about half the other outlets will see the
signal.  putting a .1 600v cap across both hot lines will help with this
problem.

-bill von