2008 Jeep Commander Owner Manual - Page 211

UNDERSTANDING YOUR INSTRUMENT PANEL 211 Two Types of Signals There are two basic types of radio signals...AM or Amplitude Modulation, in which the transmitted sound causes the amplitude, or height, of the radio waves to vary...and FM or Frequency Modulation, in which the frequency of the wave is varied to carry the sound. Electrical Disturbances Radio waves may pick up electrical disturbances during transmission. They mainly affect the wave amplitude, and thus remain a part of the AM reception. They interfere very little with the frequency variations that carry the FM signal. AM Reception AM sound is based on wave amplitude, so AM reception can be disrupted by such things as lightning, power lines and neon signs. FM Reception Because FM transmission is based on frequency variations, interference that consists of amplitude variations can be filtered out, leaving the reception relatively clear, which is the major feature of FM radio. NOTE: The radio, steering wheel radio controls (if equipped), and 6 disc CD/DVD changer (if equipped) will remain active for up to 10 minutes after the ignition switch has been turned off. Opening a vehicle front door will cancel this feature. 4