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DIDS-402-2AM13
CHAPTER 1
GENERAL INFORMATION
1 -1
PURPOSE OF EQUIPMENT
The Model 402 -2AM13 Display Terminal (figure 1-1) is a radio frequency
(rf) shielded display device designed to provide quick-action keyboard input and
visual readout of information stored or processed by a central processing unit (CPU
The Display Terminal ope rate s in one of two separate mode s: transmit or receive.
In the transmit mode, display terminal operators initiate messages by
operating keys on the keyboard assembly.
As each character key is depressed,
a visual character corresponding to the particular key is produced on the cathode
ray tube (CRT) screen.
Simultaneously, a digital code corre sponding to the
particular character enters an internal memory device.
When the operator has
completed composing the message, the message is coupled through self-contained
interface circuits to either a modem or a CPU Input/ Output (I/O) device.
This
readout is non-volatile, and the message remains on the screen even though the
data is transmitted.
In the receive mode, digital data messages arriving from the CPU are
decoded by the Display Terminal and visual characters are produced on the CRT
screen.
Again, the data received is simultaneously stored in a memory device;
if desired, the received message may be edited and returned to the CPU.
In
addition to receiving actual data characters, the Display Terminal recognizes
several control codes.
These codes produce a message which is formatted
according to the CPUls programmed directives.
Depending upon the nature
of the information system, received data may be edited and returned to the CPU,
or destroyed after noting the displayed information.
1-2 DESCRIPTION OF EQUIPMENT
The Display Terminal is a compact, solid- state device completely self-
contained in an rf shielded cabinet.
All interface connections conform to inter-
face standard MIL-STD-l88B and interfacing signals enter and exit through a
single connector at the rear of the unit.
Data transfer between the Display
Terminal and the connected I/O device is asynchronous and occurs at a rate of
1200 bits/sec (baud).
The Display Terminal uses a monoscope character generator to produce
96
separate visual characters.
These characters consist of the upper and lower
case alphabet, numerals 0 through
9,
and several special symbols.
Up to 1040
high-resolution characters can be displayed on the CRT screen at any given
moment in an 80 character/line, 13-line format.
Extensive editing and cursor
control increases operational flexibility"by allowing operators to rapidly revise
and update the information, correct errors, or arrange transmitted data messages
in a particular format.
All composition and editing of data m.essages is accom-
plished off-line; the Display Terminal is connected to the CPU only during the
actual transfe r of information.
1-1
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