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The magnetic head
is
positioned over the desired track by means of a stepper motor/band assembly and its asso-
ciated electronics. This positioner employs a one-step rotation to cause a one-track linear movement. When a
write-protected diskette is
inserted
into the disk
drive,
the Write Protect sensor disables the write electronics of
the disk drive, and a Write Protect output signal is applied to the interface.
When performing a write operation, a 0.33 mm (0.013-inch) (nominal) data track
is
recorded. Then, this track is
tunnel erased to 0.30
(0.012
inch) (nominal).
Data recovery electronics include a low-level read amplifier, a differentiator, a zero crossing detector, and digitiz-
ing circuits.
No data decoding ability is provided in the basic disk drive.
The disk drive is also supplied with the following sensor systems:
1.
A Track 00 switch that senses when the Head/Carriage assembly
is
positioned at Track 00.
2.
The Index sensor, which consists of a LED light source and phototransistor, is positioned
such that a digital signal
is
generated when an index hole
is
detected. The Index sensor is a
high resolution device that can distinguish holes placed close together, i.e., index sector
holes in a hard-sectored diskette.
3.
The Write Protect sensor disables the disk drive write electronics whenever a write-protect
tab is applied to the diskette (see Section 1.13).
1.4
DISKETTES
The disk drive uses a standard 133.4 mm
(5.25
inch) diskette. Diskettes are available with a single index hole or
with index and sector
holes.
Single index hole diskettes are used when sector information is pre-recorded on the diskette. Multiple index hole
diskettes provide sector pulses by means of the Index sensor and
electronics.
1.5
MECHANICAL AND ELECTRICAL SPECIFICATIONS
The mechanical and electrical specifications of the disk drive are listed
in
Table 1-1.
1.6
INTERFACE CIRCUIT SPECIFICATIONS
The interface circuits are designed so that a disconnected wire results
in
a false signal.
Levels:
True
=
+
0.4 V
(maximum)
False
=
+
2.4 V
(minimum)
1.7
UNCRATING THE DISK DRIVE
The disk drive is shipped in a protective container which, when bulk packaged, minimizes the possibility of dam-
age during shipment. The following procedure
is
the recommended method for uncrating the disk drive.
1.
Place the shipping container on a flat work surface.
1-2
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