In A-mode displays, which statement best describes how the display is generated?

In A-mode displays, which statement best describes how the display is generated?

• A. The dot moves at a constant speed across the system's display; the reflection is processed; the moving dot is deflected upward.
• B. The dot moves at a constant speed; the reflection is processed; the moving dot is deflected downward.
• C. The dot remains stationary; the reflection is processed; the moving dot is deflected upward.
• D. The dot moves at a variable speed; the reflection is processed; the moving dot is deflected upward.

Answer: (A)

In A-mode displays, the system fires a single pulse and uses the time it takes for echoes to return to map depth, while the echo strength determines how far the trace moves from the baseline. The display is generated by a dot that sweeps across the screen at a constant speed, representing time (and thus depth). When an echo is received, the dot is deflected upward by an amount proportional to the echo’s amplitude, producing a spike. This combination—constant sweep speed, processing of the reflection, and upward deflection for the echo—perfectly describes how A-mode displays are created. If the speed varied, or the dot deflected downward, or the dot remained stationary, the depth information or amplitude would be misrepresented, which is why those descriptions aren’t accurate.

In A-mode displays, the system fires a single pulse and uses the time it takes for echoes to return to map depth, while the echo strength determines how far the trace moves from the baseline. The display is generated by a dot that sweeps across the screen at a constant speed, representing time (and thus depth). When an echo is received, the dot is deflected upward by an amount proportional to the echo’s amplitude, producing a spike. This combination—constant sweep speed, processing of the reflection, and upward deflection for the echo—perfectly describes how A-mode displays are created. If the speed varied, or the dot deflected downward, or the dot remained stationary, the depth information or amplitude would be misrepresented, which is why those descriptions aren’t accurate.