Mobile phone mast. Mobile telephones receive and send voice, text and image data as low-intensity microwaves. The signals are relayed through a network of antennas that are mounted on masts. The main masts are typically 15 metres high with antennas that have a range of a few hundred metres in urban areas. There are two types of antenna. The rectangular ones (top of mast) transmit to and from mobile phones in the coverage area, while the round antennas (not seen) transmit between masts. There are concerns about the effects on humans of microwave radiation from mobile phones and antennas. Photographed in Andalucia, Spain, in October 2004.