4th Generation iPod

The fourth generation (4G) iPod introduced the click wheel that we’re all familiar with today. Rather than 4 buttons surrounding the scrollwheel or a row of buttons above the scrollwheel, these functions are now controlled on the scrollwheel itself, a feature that had arrived with the iPod mini in January 2004.

4G iPodThe four buttons that once surrounded the scroll wheel are now part of it with menu on the top, play/pause on the bottom, previous track on the left, and next track on the right. The button at the center of the scrollwheel is the select button.

This was the first full-sized iPod that could be charged via USB 2.0 rather than requiring a FireWire port on your Mac or PC – or an AC adapter with a FireWire port.

Even more efficient than the 3G iPod, the 4G can run up to 12 hours from a full charge.

Unlike competing devices that used MP3 file compression, the iPod with iTunes was designed to use the superior AAC (Advanced Audio Coding) audio format in addition to MP3. AAC generally provides superior sound quality over MP3 at the same bit rate, especially at 96 kbps and lower sampling rates, as well as more efficient encoding, which means smaller files.

Hardware Overview


  • Announced: 2004.07.19 at US$299 (20 GB) and $399 (40 GB).
  • Included accessories: earbuds, AC adapter, FireWire and USB 2.0 30-pin dock cables, dock (40 GB only), iTunes CD
  • Code name: Q21
  • Model number: A1059
  • Product numbers:
    • M9282, 20 GB
    • M9268, 40 GB


  • CPUs: 2 ARM 7TDMI-derived CPUs running at variable speeds up to 80 MHz
  • Audio chip: Audio Codecs developed by Wolfson Microelectronics
  • Display: 2″ 160 x 128 pixel LED-backlit LCD.
  • Battery: 600 mAh lithium polymer
  • Charge time: 4 hours max.
  • Play time: 12 hours


  • Original OS: iPod OS 3.0
  • Maximum OS: iPod OS 3.1.1
  • iTunes Versions: iTunes 4.6 and later.
  • Mac OS Required: OS X 10.1.5 or later, 10.3 or later recommended. 10.3.4 required for USB 2.0 support.
  • Windows Versions Supported: 2000 SP4, XP Home or Professional

Dimensions and Weight

  • Dimensions: 4.1″ x 2.4″ x 0.57″ (20 GB) or 0.69″ (40 GB)
  • Weight: 5.6 oz. (20 GB) or 6.2 oz. (40 GB)

Further Reading

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Short link: http://goo.gl/Ca9zKB

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