The proceedings at the high-security, high-tech courtroom due to host the trial of five alleged plotters in America's worst terror attack, September 11, are heard in the press gallery and in a room where human rights groups and victims' families sit, with a 40 second delay.

This is done so a court security officer, or CSO, sitting next to the judge can block anything deemed classified.

The officer has two switches -- "stop" and "go" -- and spectators behind a thick glass window can see a red light go on when proceedings are in fact being silenced.

Judge James Pohl disclosed Thursday that the government -- by means of the so-called original classification authority (OCA) -- also has a switch, but outside the courtroom, that allows it to cut off the broadcast of the proceedings.

On Monday part of the proceedings were censored when the discussion touched on secret CIA prisons where the suspects were held and abused.

The judge said he was surprised and angry that the censoring mechanism was activated from outside the court, without his knowledge.

This must stop, Pohl said, adding that "the judge and only the judge" can decide what happens in his courtroom.

On Thursday, the last day of this round of hearings, Pohl said the government must "disconnect the outside feed or ability to suspend the broadcast" from outside his court.

The ruling means censoring can go on, but it cannot be activated from outside the courtroom.

The judge said the "public has no unfettered right to access classified info. However, the only person who is authorized to close the courtroom is the judge."

"This order takes effect immediately," he said.

The Justice Department prosecutor in charge of classified material questions, Joanna Baltes, had said the OCA had the possibility of controlling the outside feed.

It was the CIA who ran the secret so-called black site facilities where terror suspects were subjected to "enhanced" interrogation methods that many people said were tantamount to torture.

Pohl insisted it was the judge and only the judge who could authorize the court security officer to control what came out of the courtroom.

Thursday was the last day of the latest session of pre-trial hearings. The five defendants, including self-proclaimed 9/11 mastermind Khalid Sheikh Mohamed, were not present as they are boycotting the sessions.

The 9/11 trial at this US base on the southeastern tip of Cuba is not expected to start for at least a year.

The five men accused of plotting the suicide airliner attacks against the Twin Towers and the Pentagon face the death penalty if convicted. The attacks left nearly 3,000 people dead.

Before Pohl's ruling, defense attorneys filed an emergency request seeking to suspend the proceedings on grounds that a dispute over the confidentiality of their conversations with their clients had not been resolved.

David Nevin, lawyer for Mohamed, said all his conversations with his client -- including during prison visits and even in the courtroom -- are being recorded.

The next hearings are scheduled to begin February 11, and the confidentiality issue is to be addressed. Pohl has ordered the defendants be present for that hearing.