Emanuel aides have said if the mayor were to move forward and pursue the tax hike, he would use it for "needed modernizations and operations at our 911 center." If approved by aldermen, the tax could generate as much as $27 million per year for the city, based on its previous returns. If officials were to spend the money on improving the 911 service, that would free up extra money elsewhere that the city planned to spend on the 911 center.