Rosewill RCW-605. - Manual (Page 7)

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User Manual USB TO IDE 2.5”+3.5”+SATA Cable RCW605
6. LED indicator meaning
a. When LED is off, RCW605 is not working now.
b. When LED is dim, RCW605 is stand by now.
c. When LED is illuminated, the hard dirve is transferring or reading its data now.
( The LED will not be illuminated when RCW605 is working with ATAPI device.)