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Maximum USB length

Discussion in 'Recording' started by Prolab, Feb 14, 2003.

  1. Prolab

    Prolab Guest

    I am running a projector from a laptop and the distance is 50 feet from the laptop rack to the ceiling mounted video projector. SVGA and USB are required to do what I require to the projector from the laptop (Toshiba)

    Since no one has a 50' USB, I ran a #432 cable. (6 Pair each pair indivigually shielded). I am going "wire to wire" for pinout.

    I understand that a USB contains the following:

    +/- Voltage
    Digital I/O

    Questions are this:

    Will 50 feet work?

    Is their one cable of the bunch that needs indivigual shielding?

    This will be used in a moderate to low RF environment...not really noisy.

    Thanks in advance
  2. AzureCrystal

    AzureCrystal Active Member

    Aug 14, 2001
    Hiya Prolab; I know you can have a USB cable to up to 80 feet, but dunno where you can buy one that long, there is a place in WPB you can make it to order: Universal PC (In Lake Worth, right by the Turnpike exit) Universal PC - 7753 Lake Worth Rd. • Lake Worth, FL 33467 Tel: (561) 968-4488 Hope this helps !! -Steve ;)
  3. llornkcor

    llornkcor Active Member

    May 8, 2001
    Brisbane, Australia (originally Boulder, CO, USA)
    Home Page:

    "In practice, the USB specification limits the length of a cable between full speed devices to 5 meters (a little under 16 feet 5 inches). For a low speed device the limit is 3 meters (9 feet 10 inches)."

    "Q3: Why can't I use a cable longer than 3 or 5m?
    A3: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ."

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