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LaCie SAFE Hard Drive
User Manual
page 38
Troubleshooting
TeChNICAl NOTe: Technically, you can
connect up to 127 devices to a single USB bus.
For more than two devices, you must make new
connections using a peripheral called a "hub."
A hub, which you hook up directly to a USB
connector on your computer, usually has 4 or 7
output connections enabling you to connect the
same number of peripherals. One of the hub's
main functions is to regenerate signals that lose
part of their strength as they are transmitted via
the USB cable. By connecting yet another hub
to a connector on the existing hub, you can then
plug in a new set of peripherals and so on, up to
a maximum of 127.
You can use your USB 2.0 devices with USB
1.1 hubs, but the peripherals will be limited
to USB 1.1 performance levels. As USB 2.0 is
backwards compatible, you will be able to con-
nect USB 1.1 devices to USB 2.0 hubs; howev-
er, the USB 1.1 devices will still maintain their
normal performance levels (i.e. 12 Mb/s).
In practice, users who desire enhanced
USB 2.0 throughput will need to connect their
USB 2.0 hardware on both ends of a 2.0 hub
to achieve the "high-speed" mode. On one end,
a USB 2.0 compliant host controller resides on
the host PC to manage the enumeration pro-
cess and power management. On the other end,
USB 2.0 hardware must be connected directly
to the root hub or through a USB 2.0 hub.
Some hubs have no power supply and others
are self-powered. When you choose a hub, opt
for the self-powered variety, as they have their
own AC adapter. e most powerful hubs pro-
vide 0.5A of power to each port. If you buy a
hub, make sure that it supports per-port switch-
ing. is function prevents the entire chain of
peripherals from freezing up if one of them is
not working properly or is down.
ImpOrTANT INfO:
Avoid using USB connectors found on cer-
tain peripherals such as keyboards. ese are
passive (or pass-through) connectors that
lead to power loss and unstable operation.
• Only use USB cables shorter than 5 meters
(approximately 15 feet). Using longer cables
cause the peripherals to malfunction due
to excessive reduction in electrical signal
strength.
•