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USB FAQ
What is USB? USB ("Universal Serial Bus") standard supports computer peripherals, such as keyboards, mice, and storage devices. It is also used on consumer items such as PDA's and cell phones.

USB 1 devices are slow, running at a maximum of 1.5 MB/sec
USB 2.0 devices will run at up to 40 MB/sec.
USB Comparison table
USB 1.1 For peripherals like keyboards, mice, etc.
Transfer rate: 1.5 MB/sec
USB 2.0 For external hard drives, usb drives, card readers, printers, scanners, etc.
Transfer rate: 40 MB/sec
Are USB 1.1 devices compatible with USB 2.0 devices? Yes, both types may coexist.
  • USB 1 and 2 devices can mix and match on the same comptuter or hub.
  • USB 1.1 hubs will work fine on USB 2.0 ports, but still run at 1.1 speeds.
  • USB 2.0 hubs can be used on older USB 1.1 computers.
  • What do the connectors look like?
    Type A Used on most USB devices. The computer's USB ports are type A.
    Type B Found on USB hubs. USB hubs connect to computers using USB A-B cables.
    Mini-USB, 4 pin Used on portable devices such as cell phones and cameras.
    Mini-USB, 5 pin Used on portable devices such as cell phones and cameras, and external data storage devices, such as hard disk drives and optical disc drives.
    Micro-USB Significantly smaller than and designed to replace Mini-USB. Used on smartphones and PDA's.
    What is the maximum length of USB cables? 5 meters. However, USB hubs may be added to acheive longer runs.

    USB on Wikipedia