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DIDS-402....;2MIO
Para 3 -1. I / 3 -1. 2
The delay-line refresh-storage circuit consists of amplifier A
10
and a
7. 378-ms magnetostrictive delay line. A 15.
The six-bit digital information
that was inserted in the refresh-storage is fed back through a part of the display
logic to the character entry and readout register to complete a cycle.
It con-
tinually circulates around the loop.
The character readout register (a group
of flip-flops) stores the six bits and applies them to the digital-to-analog (D/A)
converter circuits of monoscope deflection amplifier A3.
The six bits of data at the output of the character readout registe rare
designated as:
DAX,O}
DAXI
DAX2
X-Deflection
DAYO}
DAYI
'
DAY2
Y -Deflection
3-l. 1 X-Deflection.
The three least significant bits (LSB ' s), DAXO, DAXI.
and DAX2, are converted from digital information to analog information in the
D/A converter of monoscope deflection amplifier A3.
This analog voltage is
combined with the ramp and skew voltages, amplified by the X-deflection ampli-
fier, and applied to the X-axis deflection plates in the monoscope.
The X-axis analog voltage positions the beam on the appropriate vertical
column of characters.
The ramp voltage (a simple sawtooth) derived from each
unblanking pulse moves the beam from the left to the right side of each character.
(The ramp generator is located on the A3 board.) The I skew in-II (derived by
sampling the Y -deflection voltage) is a correction voltage used to compensate
for any slight angular difference between the X -axis line of characters and the
X-axis sweeps.
Figure 3-2 shows the monoscope character generator technique.
Figure 3-3 is the modified ASCII (American Standard Code for Information
Interchange) character matrix used in the monoscope.
3-1. 2 Y -Deflection.
The three most significant bits (MSB IS), DA YO, DAY 1,
and DA Y2, are converted from digital information to analog information.
The
resulting analog voltage is combined with the minor vertical sweep expansion
and the skew voltage, amplified by the Y -deflection amplifier. and applied to
the Y -axis deflection plates in the monos cope.
The Y -axis analog voltage positions the beam on the appropriate hori-
zontalline of characters.
The 583-kHz sine wave modulates the Y-axis analog
voltage so that the beam paints up and down over the character height.
The
I skew in-2 I (derived by sampling the X -deflection voltage) is a correction
voltage used to compensate for any slight angular difference between the Y-axis
line of characters and the Y-axis sweep.
As the beam sweeps 'up and down at
583 kHz, it moves rapidly from left to right across the character.
When it
strikes the character, it varies the output current in the input circuit of the
monoscope preamplifier A 7, causing the voltage to change and appear as video.
This video is further amplified by video amplifier A8 and applied to the cathode
of .the display CRT.
The 583-kHz voltage applied to the minor vertical sweep
COlI (about the neck of the CRT) is produced from the same circuit that generated
the 583-kHz voltage sweeping across the letter in the monoscope tube.
Thus,
the letter is reproduced on the display CRT.
The Shift Off Screen (50S) signal
3-5
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