The New York Police Department has quietly flipped the switch on a high-tech command center designed to protect lower Manhattan from terrorist threats.

The center, located in a nondescript office tower, is part of an ambitious $100 million security initiative launched in response to the Sept. 11, 2001 terrorist attack on the World Trade Center.

Earlier this month, about 30 officers assigned to the command center for the first time began monitoring 150 closed-circuit cameras trained on Wall Street. Police say there will be 3,000 cameras in the financial district by 2011.

The program was modeled in part after the "ring of steel" surveillance measures in London's financial district. But Police Commissioner Raymond Kelly says it will exceed that effort in scope and sophistication.