sentences:  The information signal can be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing data from a computer.In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency, called the "carrier wave" because it serves to "carry" the information through the air.The information signal is used to modulate the carrier, altering some aspect of it, "piggybacking" the information on the carrier.