Physical devices

USB Flash Memory HOWTO
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# 2. Physical devices

Flash memory devices come mainly in the form of small, portable devices often referred to as memory sticks or keychains, and as part of digital cameras. They are non-volatile devices which operate on the principle that electric charges are used to represent data in binary format. These charges can remain unchanged almost indefinitely, but changes (such as writing to the device) limit the life span of the device (100000 writes of 8MB each).

Memory sticks plug directly into a USB-port at the back of your computer. The power it needs is supplied by the USB-port. It is sometimes convenient to use a USB-extension cable to bring the device within easy reach.

Memory sticks usually have write protect switches which should be turned off if you want to use it as read-write device. If the switch is in the "on" position, the device is read-only. The devices are usually equipped with a led (light emitting diode), which indicates that the device is operational. The led also flickers while data is being transferred to or from the device.

Digital cameras use flash memory for image storage. These are powered by the camera and connected to the computer's USB-port via an electronic interface. To be able to connect to the computer, the camera's power must be turned on for the duration of the interfacing, and should only be turned off after the device had been unmounted from the computer. It is important to remember that the device takes power from the camera's battery. The operation should therefore be terminated as soon as possible.

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