Ancient Wall

The Ancient wall opens using a sub-sonic tone

"I've set up a sub-sonic tone generator outside. The wall is now permanently open."
Rodney McKay[src]

The sub-sonic tone generator was a device used by the Tau'ri to emit a special type of sound.

In 2008, when Rodney McKay and Daniel Jackson found Janus' secret lab in Atlantis, they used a sub-sonic tone generator to keep the Ancient wall, that was blocking the entrance, open without the need to use the three sonic devices outside the laboratory. The generator was activated so that the wall wouldn't break apart the body of a person going through it if the sound emitted by the three lights happened to go off while a person was still going through the wall. (SGA: "First Contact")

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