FCC Commercial Element 8 pool, section 29

Subelement D

Display & Control Systems

Section 29

Displays

829D1

Modern liquid crystal displays have a pixel count of:

Correct Answer
A.
Greater than 200 pixels per inch.
B.
Greater than 50 pixels per inch.
C.
Can have no more than 125 pixels per inch.
D.
Can implement 1,000 pixels per inch.

829D1

Modern liquid crystal displays have a pixel count of:

(A). Greater than 200 pixels per inch.

It must have been a long time since the 200 pixels displays were used. An easy answer to pick as other choices limit the number of pixels well below what is in use.

A good discussion on radar displays is listed on the Practical Sailor site, article Entry-Level LCD Radars

For historical and technical overview, please see Zoboko site for the article 2.8 The Radar Display and User Controls

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829D2

Voltages used in CRT anode circuits are in what range of value?

A.
0.5-10 mV.
Correct Answer
B.
10-50 kV.
C.
20-50 mV.
D.
200-1000 V.

829D2

Voltages in a CRT - Cathode-Ray Tube, as in old analog TV sets, are high enough to generate short-range X-rays and are lethal.

Pick the answer with the highest voltages!

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829D3

The purpose of the aquadag coating on the CRT is:

A.
To protect the electrons from strong electric fields.
B.
To act as a second anode.
C.
To attract secondary emissions from the CRT screen.
Correct Answer
D.
All of the above

829D3

AQUADAG - Aqueous Deflocculated Acheson Graphite is a conductive graphite coating used inside CRTs - Cathode Ray Tubes (as in older analgo TVs) to improve CRT properties by doing all of A., B. and C.

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829D4

LCD patterns are formed when:

Correct Answer
A.
Current passes through the crystal causing them to align.
B.
When voltage is reduced to the raster scan display.
C.
When the deflection coils are resonant.
D.
When the ships antenna's bearing is true North.

829D4

LCD - Liquid Crystal Displays contain molecules floating in a liquid. When a voltage is applied to a particular pixel, the molecules floating over that pixel will all align and let the background light through thus causing the pixel light-up.

The molecules line-up in an electric field because they are highly polarized, meaning one end of the molecule has a positive charge while the other end has an equal negative charge.

When a voltage is applied to a pixel, the positively charged end of the molecule will be drawn to the pixel's negative electrode, while the negatively charged end of the molecule will be drawn to the pixel's positive electrode.

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829D5

In a raster-type display, the electron beam is scanned:

A.
From the center of the display to the outer edges.
Correct Answer
B.
Horizontally and vertically across the CRT face.
C.
In a rotating pattern which follows the antenna position.
D.
From one specified X-Y coordinate to the next.

829D5

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829D6

Select the statement, which is most correct regarding a raster scan display.

A.
Raster displays are the same as conventional T.V. receivers.
B.
The scan rate for a RADAR system is 30 frames per second.
Correct Answer
C.
Raster scanning is controlled by clock pulses and requires an address bus.
D.
Raster scanning is not used in RADAR systems.

829D6

To avoid deforming an image, a display using a raster scan (as in old analog TVs) must "scan" the display from left to right and from top to bottom with exquisite precision, a precision that can only be achieved via a controlling clock, thus Answer C. is the right answer.

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