SECTION 1
GENERAL DESCRIPTION
1.1
INTRODUCTION
This manual contains ageneral description, instal-
lation
and
operating instructions, theory
of
operation,
and
maintenance information for the
Lear
Siegler
ADM-3A
Interactive
Display
Terminal.
Additional information
is
contained in the
AD
M-
3A Operator's Handbook. The maintenance
technician should be thoroughly familiar with
material in the Operator's
Handbook
before
attempting
to
troubleshoot
or
repair the ADM-3A.
1.2 ADM-3A CAPABILITIES
The
ADM-3A
has
the
following
general
capabilities:
a.
Receives USASCII-coded
data
from aremote
computer
and
displays it
on
a
CRT
screen
displaying up to 1920 characters.
b. Permits the operator, using akeyboard,
to
compose amessage, visible
on
the screen as it
is
transmitted to the remotecomputer
or
other
device.
c.
Through
an
extension
port,
permits
interfacing with ahard-copy printer, magnetic
tape recorder,
or
other terminals.
d. Provides for full-duplex
or
half-duplex
communications,
through
either
an
RS-232C
or
current-loop interface.
e.
Permits 202 communications line
turnaround
by means
of
either
EOT
or
ETX code-
turnaround
(in which the controlling device
transmits a
turnaround
code
to
give control
to
the device
at
the other end
of
the line),
or
secondary-channel
turnaround
(in which a
secondary channel selection establishes
control
of
adevice for
data
transmission
through
the primary channel).
f.
Allows the
operator
to select between adouble
underline cursor which enters
data
on
the
bottom
line,
or
areverse block cursor homed
at
the
top
left
of
the screen.
1-1
g.
The terminal has the ability to recognize and
position the cursor
at
any location on the
screen.
h. The ADM-3A contains
an
overflow detector
which causes wrap-around
or
scrolling on
forward
or
downline operations and allows
the cursor to be 'homed.'
1.3 PHYSICAL DESCRIPTION
Principal components
of
the
ADM-3A
are as
follows:
a. Amolded case comprising abase and acover.
The base contains the power switch, power
transformer,
beeper
speaker,
and
intercomponent cabling. The main circuit
board
rests
on
supports molded in the base
and
is
held in place by two guide pins.
The cover contains the monitor
CRT
and
other monitor subassemblies.
It
is
hinged at
the rear so
that
all components
of
the
ADM-
3A are accessible when it
is
opened. The cover
is
easily removed by swinging it back
as
far as
it will go, and then sliding it to the left, offthe
hinge pins. (The monitor-connecting cable
must be disconnected.)
b. The main circuit
board
which contains all
elements
of
the
ADM-3A
except monitor,
power switch, line fuse
and
transformer, and
beeper speaker. The keyboard consists
of
integrated key rows and
is
built directly
on
the
main circuit board.
The main circuit board rests
on
supports
within the base
and
is
held in place by guide
pins. Two connectors
on
the rear edge
of
the
board
provide the RS-232C
and
current loop
(optional printer port) interface
at
both
the
main and extension ports.
c.
The
CRT
monitor which compnses three
subassemblies,
-as
follows:
1.
The
CRT
itself, which
is
mounted in a
metal frame with its face held against the
cover bezel by two brackets, each retained
by asingle screw.
