It's estimated there are 3.5 cellular telephone users in the world today, with that number rising all the time; cell phone towers are now a common sight in most major cities, and some service providers camouflage the towers, placing them inside chimneys or water towers. But are they disguising the towers in the name of urban beautification or to hide a potential health menace? Some scientists have questioned the safety of cellular phones, suggesting that the signals can have a detrimental effect on people's health, and a growing number of people have reported ill effects brought on by proximity to cell phones and signal towers. Filmmaker Talal Jabari examines the controversy behind cell phones and the signals that make them work in his documentary Full Signal, in which he interviews doctors to discuss the impact of cellular signals on the human body, the efforts of the telecommunications industry to prevent further regulation of the cell phone business, and activists fighting for greater transparency regarding the location of cell towers. Full Signal was an official selection at the 2010 Big Sky Documentary Film Festival.