Brief History

• USB--universal serial bus--technology has evolved though a few versions, starting with 1.0 in the early 1990s to the recently announced USB 3.0 technology. In between, and the standard as of 2010, is USB 2.0, which is some 40 times faster than the 1.0 technology. Most USB devices require USB 2.0 to function correctly (to receive enough power). Older devices, using USB 1.0, require shorter cables and the 1.0 interface is limited in how much power it outputs.
  
  

Standard Cables

• Most USB cables are between 3 feet and 16 feet long. The length of cable depends largely on the kind of device it powers, the type of USB and its effectiveness. Shorter cables are usually preferred.
  
  

Limitations

• Think of USB cables as power cords with a twist. The electrical structure of the USB interface doesn't allow for the electrical current to be transmitted over great distances, as with an extension cord for a power tool. The designers of USB technology deemed the short distances obtainable by USB cables acceptable, since all dependent technology is designed for a small, desktop environment.
  
  

Cable Lengths

• The maximum recommended distance for a standard USB device is 5 meters, or 16 and a half feet. If you need to run a USB device beyond this length, you can buy self-powering USB couplers that link cables together, up to a maximum of five cables.