Specifications
15
TRAVELDRIVES—USB PORTABLE MEMORY
TravelDrives are not really drives at all since nothing moves
inside. They are flash memory devices in the shape of small
cartridges no larger than a thumb. One end of the device is a
USB connector that plugs into a USB port so that the computer
recognizes the device as a removable drive. The fact that the TravelDrive is solid-state memory
and not a real mechanical drive means that it is a durable, safe, and reliable means of storing or
transferring files. A real drive in such a small form is both more expensive and delicate. The small
shape and lightweight design of many of these USB portable devices make them suitable for
sticking them in a pocket or even attaching to a key chain with little worry about any damage to the
memory card or to the data stored on it. TravelDrives also have two built-in protection features:
1) a locking write/protect tab to prevent accidental erasure of important files (not on all models); and
2) a warning LED that lights when the device is attached to a USB port and flashes as data are
transferred to the device. The flashing LED is a reminder not to remove a TravelDrive while data
are being transferred to or from the drive in order to prevent corrupted files.
TravelDrives contain memory chips with capacities of up to 8GB and a USB controller for
transferring files. PCs with Windows ME/2000/XP/Vista and Apple Macintosh OS from 8.6 and
newer accept these USB portable memory devices as plug and play removable memory and,
therefore, need no drivers to use them. Windows 98 and 98SE require the installation of a driver in
order to recognize these USB storage devices, and drivers are sometimes included with them.
All recent Memorex TravelDrives are USB 2.0-compatible devices, which means that they can
transfer data through a USB 2.0 port more than ten times faster than through a slower USB 1.1
port. The USB 1.1 and USB 2.0 TravelDrives can be used in either type of USB port, but the 2.0
version will deliver its higher transfer speed only in the faster USB 2.0 ports.
The memory chip used in USB flash devices and in all flash cards is known as a NAND-type EEPROM.
“NAND” means “not and,” a type of memory logic referred to as Boolean logic after George Boole, who
argued that logic was a mathematical, not philosophical exercise. Boole devised a logic system in 1853 that
consisted of different types of logic “gates” that define the steps in coming to a logical conclusion. An AND
gate would mean that if one input were a value of 1 AND a second input were also 1, the result is a 1, too.
The NAND gate is the opposite: under the premise above that Input #1 AND Input #2 are both values of 1,
the result is 0. The NAND logic has a counterpart known as ”NOR-type” (“not or”) logic. By arranging a
series of different interconnected electrical logic circuits, the final results will always be “remembered” as
either a value of 1 or 0 depending on the inputs. That’s how the circuit attains its “memory.” Unless one is a
mathematician or a computer engineer, it is easier to distinguish NAND logic from NOR logic by the layout of
the memory cells. Memory cells in NAND chips are arranged in series while the NOR memory cells are
arranged in parallel. NAND chips have fast write and erase abilities because they write in small blocks of
information rather than in single bytes. What NAND architecture gains in read/write speeds, however, it