Inside the NASDAQ Tower

Inside the tower is a workstation where one person decides what will go on the sign. And this is more complicated than it seems. For example, there are holes in the sign that accommodate windows, and when an ad goes up, it often needs to be adjusted so the words don't land in those holes. To this end, the operator can move pieces around. To help, there's a camera located in an office on the other side of Times Square that lets the operator see what the sign looks like to the outside world.

©2007 HowStuffWorks This camera inside the operator's station keeps an eye on the sign for potential mistakes.

From the operator's station, data flows to a whole rack of computers and controllers that break down the image and figure out how every individual pixel must be lit. These machines format the data that goes to the tiles, and the tiles then decode the data to create the correct image.

©2007 HowStuffWorks The computers pictured on the left control the NASDAQ MarketSite Tower. ­

The sign itself uses about 500,000 watts when all the LEDs are on. That doesn't count the power used by the 12 air conditioning units. The tiles and their LEDs turn all of that power into light. The light is able to produce an stunning, bright color display that can be clearly seen both day and night.

For more information on the NASDAQ Tower, the stock market and related topics, see the links on the next page.