Fujitsu MAH3091MC - Enterprise 9.1 GB Hard Drive Product/Maintenance Manual page 27

The actuator positions heads on the CCS zone over the disk and is locked by the mechanical lock
when the power is off or the spindle motor is stopped.
(5) Air circulation (recirculation filter, breather filter)
The heads, disks, and actuator are hermetically sealed inside a disk enclosure (DE) to keep out dust
and other pollutants. The DE has a closed-loop air recirculation system. Using the movement of
the rotating disks, air is continuously cycled through a filter. This filter will trap any dust
generated inside the enclosure and keep the air inside the DE contaminant free. To prevent
negative pressure in the vicinity of the spindle when the disks begin rotating, a breather filter is
attached. The breather filter also equalizes the internal air pressure with the atmospheric pressure
due to surrounding temperature changes.
(6) Read/write circuit
The read/write circuit utilizes a read channel mounted with a head IC that supports high-speed
transmission and an MEEPR4ML (Modified Enhanced Extended Partial Response Class 4
Maximum Likelihood) modulation/demodulation circuit in order to prevent errors being triggered
by external noise and to improve data reliability.
(7) Controller circuit
The controller circuit uses LSIs to increase the reliability and uses a high speed microprocessing
unit (MPU) to increase the performance of the SCSI controller.
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