Re: TV Detecotrs (was They don't take bookings for individuals on Friday, Satruday and Sundays)

On Wed, 30 Nov 2005 15:38:21 +0000 someone who may be Ian Blake
<NoNotMe@NotAnywhere> wrote this:-

>>Cathode ray tubes emit enough radiation during the raster scan for the
>>image they are showing to be fairly reliably reconstructed through a
>>brisk wall, so detector vans certainly used to work very well.
>
>I do not believe the detector vans tried to get the picture.

I have no idea. However, should one wish to do so then there is no
great problem. Governments spend a fortune on preventing the images
on some screens being available to others to view. In reasonably
well informed circles the name TEMPEST is often used to describe
this subject, though that name is/was (I am out of date on the
subject) in fact just related to a particular part of the whole
subject.

>Apparently the pulse can also be detected on the national grid when a
>popular television program is on. Everybody adding in their little
>pulses synchronised to the local transmitter.

Signals from electrical equipment are indeed transmitted "backwards"
along electricity systems. If one can lock in on a particular piece
of equipment then one can see what it is doing, though the further
away one is from it then the more difficult it becomes to pick that
particular piece of equipment out from all the others. One can avoid
this by expensive screening and filters. Governments, large
companies and other criminals can afford this sort of thing, though
large companies are often woefully ill-informed.

For the sort of equipment members of the public are likely to have,
an LCD screen powered by batteries is about as good as one can do.
Should one want to do more then that is possible if one gets in
touch with those who know what they are doing. A television licence
is cheaper though:-)




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
.

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