They relay antennas, are both related to antennas dedicated to mobile phones as terrestrial television repeaters, radio equipment of state services such as the military, firefighters and hospitals.

The antennas are devices capable of receiving and dissemination of electromagnetic waves. They convert electrical signals into electromagnetic waves. They exist from the beginning of the wave radiators and are classified according to their frequency.
These antennas propagate radio waves are electromagnetic waves of 3 Hz to 300 MHz. Microwaves are electromagnetic waves of 300 MHz to 300 GHz.