>At 01:27 PM 1/7/01 -0500, Arnold G. Reinhold wrote:
>>"Every inch of floor in more than four buildings was covered with
>>two-by-two-foot squares of bleak brown carpet. When the astronomers
>>tried to replace it, they discovered it was welded with tiny metal
>>fibers to the floor. The result, they eventually realized, is that
>>the rugs prevent the buildings from conducting static electricity.
>>
>>Even the regular lighting looks different, covered by sleek metal
>>grids that prevent the light bulbs from giving off static
>>interference. "
>>
>>Sounds more like TEMPEST shielding.
>>
>
>It resembles TEMPEST, but shielding works both ways. The spooks chose
>the site because it was RF quiet, but had to run their computers in the
>same area as sensitive dishes. It makes sense that the shielding
>was to quiet their own emissions to help their receiving. After
>all, fluorescent bulbs don't leak much intelligence :-) but they
>sure cause electrical noise.
You may be right about their concern being to prevent interference
with their listening equipment, but I don't agree with your last
point. As I understand it, all electrical wiring coming out of a
TEMPEST enclosure has to be carefully (and expensively) filtered.
The power wiring to lighting fixtures can pick up and re-radiate
compromising signals. By shielding the fixtures, they effectively
place the lights outside of the enclosure. I'll bet the wiring to
those fixtures is within carefully grounded conduit.
It would be fun to take a tour!
Arnold Reinhold
