Allied Telesis AT-SBx31CFC960 - Manual (Page 279)

SwitchBlade x3112 Chassis Switch and AT-SBx31CFC960 Card Installation Guide
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Figure 172. Loosening the Screw on the AT-SBxFAN12 Fan Module
6. Carefully pull on the handle to disconnect the fan module from the
connector on the backplane of the chassis. Refer to Figure 173.
Figure 173. Loosening the AT-SBxFAN12 Fan Module from the Backplane
Connector