Wireless communication involves sending and receiving information through the air or through space via electromagnetic waves, most often as radio waves. Wireless devices send and receive signals over distances ranging from a few feet or meters to thousands of miles or kilometers. Many people use such small wireless communication devices as cordless telephones, walkie-talkies, pagers, and cellular telephones. The military often uses larger wireless units that can be carried or mounted in vehicles. All communications to aircraft and sea vessels are wireless. Artificial satellites relay telephone calls in the form of microwave transmissions. The remote control devices that control home electronic equipment use infrared light waves.