2008 Jeep Patriot Owner's Manual - Page 196

194 UNDERSTANDING YOUR INSTRUMENT PANEL 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. 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 six-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. ELECTRONIC DIGITAL CLOCK The clock and radio each use the display panel built into the radio. A digital readout shows the frequency and/or time in hours and minutes (depending on your radio model), whenever the ignition switch is in the ON or ACC position. When the ignition switch is in the OFF position, or when the radio frequency is being displayed, timekeeping is accurately maintained. On the AM/FM/CD (6-disc) radio, the time button alternates the location of the time and frequency on the display. On the AM/FM/CD (single-disc) radio, only one of the two, time or frequency, is displayed.