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January 20th, 2008 17:00

Active USB 2.0 Repeater Cable vs USB 2.0 powered hub

Hi,
 
I need to be able to print to two printers both 7 mtrs away from my Dimension 9150. Which of the following is best:
 
1 x 5m USB2.0 cable to USB 2.0 powered hub then 2 x   2m USB2.0 cables to each printer.
or
2 x 5m active repeater USB 2.0 cables from desktop with a 2m USB2.0 extension to each printer.
 
Help much appreciated.
 
Zippy
 
Dell Dimension 9150 running XP MCE
Dell 1720db Laser printer
Epson Stylus RX620
 

326 Posts

January 20th, 2008 17:00

A powered USB hub mainly provides extra current for
external USB devices which the main usb ports can not
provide. It will not overcome the inherent limitations of
the USB 2.0 specifications .. USB may not work properly
at lengths of over 15 meters

http://en.wikipedia.org/wiki/USB

The maximum length of a standard USB cable is 5.0 meters (16.4 ft). The primary reason for this limit is the maximum allowed round-trip delay of about 1500 ns. If a USB device does not answer to host commands within the allowed time, the host considers the command to be lost. When USB device response time, delays from using the maximum number of hubs and delays from cables connecting the hubs, host and device are summed, the maximum delay caused by a single cable turns out to be 26 ns [9]. The USB 2.0 specification states that the cable delay must be less than 5.2 ns per meter, which means that maximum length USB cable is 5 meters long. However, this is also very close to the maximum possible length when using a standard copper cable.

Using USB devices over a greater length require hubs or active extension cables. Active extension cables are bus-powered hubs equipped with two maximum length standard USB cables. USB connections can be extended to 50 m (160 ft) over CAT5 or up to 10 km (6.2 mi) over fiber by using special USB extender products developed by various manufacturers.

In practice, some USB devices may work with longer cable runs than 5 meters, if the number of hubs between the host and the device is less than the maximum number allowed by the USB standard. However, using a longer cable lowers both the signal quality and the voltage provided by the USB bus below the specification tolerance limits. This may prevent USB devices from working properly or even from working at all.

326 Posts

January 20th, 2008 17:00

I would use the powered USB Hub myself.
And it will be less costly than the repeater cables.

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120 Posts

January 20th, 2008 17:00

Thanks for that. I take it a powered USB HUB has exactly the same effect for creating a USB extension beyond 5m as an active repeater cable?
 
 

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120 Posts

January 20th, 2008 18:00

I have managed to place the powered hub just 5m away from the desktop with a fairly high quality  usb2.0 cable connecting. The two A-B USB cables then connect direct into each printer. I guess this should be ok?
 
Thanks
 
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