<P> The renewable energy systems supply electrical power when available . The fuel cells are activated only when the natural sources are not enough to supply the energy the system needs . The emergency power supply (the fuel cells) is designed to last an average of 10 days . In this way the structure is completely self - sufficient: this enables the maintenance team to pay only few visits to the site, since it is usually hard to get to . </P> <P> There is often local opposition to new masts for reasons of safety and appearance . The latter is sometimes tackled by disguising the mast as something else, such as a flag pole, street lamp, or a tree (e.g. palm trees, pine trees, cypress) or rooftop structures or urban features such as chimneys or panels . </P> <P> These concealed cell sites can distinguish themselves by foliage shape and bark type . The foliage of all these antennas is composed of leaves made of plastic material accurately designed, taking into consideration quantity, shape and array suitable to completely conceal the antennas and all accessory parts in a natural manner . The materials used guarantee absolute radio - electric transparency and resistance to UVA rays . Nicknames include "monopalm" for a monopole disguised as a palm tree or "Pseudopinus telephoneyensis" for a mast disguised as a pine tree . In monopoles, the directional antennas are sometimes hidden in a plastic housing near the top of the pole so that the crossbars can be eliminated . </P> <P> Rooftop structures such as concealment chimneys or panels, 6 to 12 meters high, may conceal one or more mobile telephone operators on the same station . Roofmask panels can be fixed to existing rooftop structures, restyling them quickly and cheaply . </P>

Most cell phone towers have a limited communication range of about one mile