The system relies on the use of sidebands, secondary frequencies that are created when two different signals are mixed. For instance, if one takes a radio frequency signal at 10 MHz and mixes that with an audible tone at 2500 Hz, four signals will be produced, at the original signals at 2500 and 10000000, as well as sidebands 9997500 and 10002500. The original 2500 Hz modulating signal is too low frequency to travel far from an antenna, but the other three signals are all radio frequency and can be effectively broadcast.[1]