That would be a shield room, not a SCIF, per se.
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You are probably referring to what I called a Screen Room. That’s what we used for High Power RF testing. The purpose was to avoid accidental exposure to high levels of electromagnetic energy if the setup leaked radiation. That didn’t really happen but it was a reasonable precaution.
And yes, that is different from a SCIF. I am working from memory but I’m pretty sure the SCIFs I worked in were shielded. I really don’t know how they did it but I assumed they used something like the Screen Room mesh embedded in the walls and ceiling.
I could be wrong but that is my recollection.
“what I called a Screen Room. “
Us electron heads call it a Faraday Cage.
screen room, shield room, two terms for the same thing. In my experience with shield rooms, which was 1988 - 2003, the walls were solid metal. The doors were airlock style, with copper “fingers” to seal in the RF.
One facility I worked in was built by the military. They tried for a gold plated facility, and used large doors pneumatically operated. One of them malfunctioned once, and started slamming shut with great force. We were lucky nobody was killed before it was fixed.