FM broadcasting was invented in 1933 and began in India in 1977 in Chennai. It later expanded to other major cities in the 1990s, nearly 50 years after taking off in the US. FM broadcasting works through the transmission of radio waves that encode sound using frequency modulation. A radio receiver then extracts the audio signal and plays it through a loudspeaker. While portable and cheaper than other media, FM broadcasts can be affected by weather and have coverage limitations.