Operators now have access to cameras throughout the city that can those cameras can give operators important information to pass along to first responders.

The 911 system is linked to police surveillance cameras around the city.

When a squad car is dispatched to a shooting scene, or firefighters roll on a chemical spill, how valuable would it be for a dispatcher to actually see and describe what the first responders will be encountering? That's the intent behind a federally financed marriage of the city's 911 system and its network of public surveillance cameras.

When a call comes in to the 911 center, the call-taker immediately sees the number and location of the call. A dispatcher then notifies police or fire, and off they go to the scene.

Now, when a call comes in, the call-taker can look at an additional computer screen that shows the locations of public surveillance cameras in the caller's neighborhood. If one of those cameras is located within 150 feet of the caller's location, it automatically feeds real-time video of the scene to the call-taker, who then shares it with the dispatcher, who then can tell the emergency responders what they're heading into.

"It's a tremendous advantage if the more intelligence you have of any situation, no matter what it is, no matter what you're going into it, the better off you are," said Ray Orozco, OEMC executive director.

In mid-December, when this 911 upgrade was in the test stage, a call came in to a call-taker of a theft in progress out in front of Macy's State Street store. The call-taker, from his position in the 911 center, was able to orient the camera on the sidewalk looking north on State and see a supposed Salvation Army volunteer who was allegedly taking loose change from the kettle and putting it in his own pocket.

"The call-taker using this technology was able to see the theft in progress and directed the responding officer," Orozco said.

Police then approached and the man with his hand in the kettle was placed under arrest. Clearly not a violent crime, but applying another set of eyes -- no matter the circumstances -- is seen by emergency responders as invaluable.

"It can help officers know how to approach. It's limitless with the potential it can do for us," said Supt. Jody Weis, Chicago Police.

There are thousands of cameras throughout the city that are now linked to the 911 center through what's called Operation Virtual Shield. The mayor is an advocate of "a camera on every corner," a desire he reiterated Thursday.

"Cameras prevent, it issues prevention. The more cameras you put on the street, the idea you prevent more crime. That is the whole issue," the mayor said.

Despite the proliferation of public surveillance cameras throughout Chicago and the rest of the country, there has been very little research done on how they impact crime fighting.

Some studies done in London, which has the world's most sophisticated network of surveillance cameras, reach the conclusion that the cameras move crime around but don't necessarily prevent it.

There is a "first-of-its-kind" study underway on the effectiveness of police neighborhood cameras, and that study has Chicago as its big-city focal point.