A subcarrier is one telecommunication signal carrier that is carried on top of another carrier so that effectively two signals are carried at the same time. At the receiving end, the main carrier and subcarrier signals are demodulated separately. A subcarrier can be used for some purpose entirely different from the purpose of the main carrier. For example, broadcast audio signals in the AM and FM ranges can carry a subcarrier along with the main audio signal. According to the U.S. Federal Communications Commission, these subcarrier channels can be used for many different purposes, "including (but not limited to) paging, inventory distribution, bus dispatching, stock market reports, traffic control signal switching,...and muzak."