Mobile phone masts near a playground. Mobile telephones send and receive voice, text and image data as low-intensity microwaves. The signals are relayed through a network of antennas that are mounted on masts. The masts are typically 15 metres high with antennas that have a range of a few hundred metres in urban areas. Hundreds of masts and smaller antennas are required to provide uninterrupted coverage across a network. There are concerns about the effects on humans of microwave radiation from mobile phones and antennas, especially on children. Photographed in Andalucia, Spain, in October 2004.