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The stored
data
in
the RT/CMOS/NVRAM are
kept
active
by
the
backup
bauery
when
the
system power
is
nol
on. If
the
stored
data
is
lost
because
of a
depleted
or
removed backup
battery, use
Easy Setup
to
restore
the
data.
EEPROM
A 64-by-
I
6 type-A EEPROM
contains the
security
passwords.
Power Management
System
The
power
management
system
controls
the
power
applied
to
the computer. This
reduces
the power drain
on
the battery
when
the
computer
power
is on,
but
not
actively
being
used.
LCD
The
VGA
LCD
supports
a
maximum
of 640 by
480 pels.
The
SVGA
LCD
supports a
maximum
of 800
by
600
pels. The
LCD
control
logic
provides
the
LCD
support
functions,
which
include
bias
voltage,
backlight
(brightness)
control
,
and
contrast control.
Prior
to
replacement
of the
LCD,
refer
to
the
notice
on
page
58.
Diskette-Drive Controller
The
controller
connects
to
the
diskette
drive
through
one,
26-pin
cable connector
on
the system
board.
Signals and
voltages
are
supplied
through
the
connector
to the
drive.
These
signals
and voltages
can
operate the computer's
3.5-inch
external
diskette
drive.
For
the standard
model,
a
CD-ROM drive
is
built
in.
For
users
that want
to
use
diskettes.
the
system
unit
has
a
connector
for
the detachable
external
diskette drive.
For
users
that
wanl
to
replace
the
CD-ROM
drive
with
a
diskette
dri
ve,
a
kit
is
provided. Both
the
internal
and
external diskette
drives
can
be
connected
at
the
same
time.
40
ThinkPad
Power
Series
820
Serial Port
The
serial
port
is
fu lly
programmable and
supports
asynchronous
communication.
The 9-pin,
D-shell
connector
provides
the
signals
to drive a standard
EIA-232D
device.
Parallel Port
The
parallel
port
a llows
the
attachment
of
devices
that
accept
eight
bits
of
paraUel
data
at
standard
transistor-transistor
logic
(TTL) levels.
The port can
be
used
as a
general
input and output port
for
any
device
or
application
that
matches
its input and
output
capabilities.
It
has
a
25-pin,
D-shell
connector
and
is
designed
primarily
for
printers.
External Input-Device Connector
The external
input-device
connector
is
located
at
the
right-rear of the
computer
and
accepts
an external
keyboard,
mouse,
or numeric
keypad.
The
keyboard/mouse
connector
(a Y-shaped connector
with
cable
and
available
an option)
must
be used when
the external
keyboard
is attached.
You
can
directly attach
an external
numeric keypad
and a
2-button/3-button
mouse
to
the
external
input-device
connector.
External Display Connector
The
display
connector is
used
to
connect
an
external
monitor.
Hardware Maintenance
Reference
41
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