Digital and Analog Signals

Question 1

A team claims digital phone lines carry speech more reliably than analog lines over long distances. Which observation is the strongest evidence for that claim?

Accepted Answer

Over 300 km, the digital call arrived clear while the analog call arrived buried in hiss and crackle.

Answer

Over 300 km, the digital call sounded louder than the analog call.

Answer

Over 1 km, the digital call and the analog call both arrived clear.

Answer

Over 300 km, the digital call reached the listener a fraction of a second sooner.

Question 2

A hospital claims digitized heart traces survive transfer between buildings better than analog ones. Which observation best supports that claim?

Accepted Answer

Every value in the digitized trace matched the original after transfer, while the analog trace arrived with added spikes.

Answer

The digitized trace was stored on a small drive, while the analog trace needed a long roll of paper kept in a filing cabinet.

Answer

The digitized trace reached the other building a few seconds sooner than the analog trace.

Answer

The digitized trace showed the same heart rate as the analog trace after transfer.

Question 3

Two probes send the same measurements through 5 km of cable that runs beside a motor adding random electrical noise. Which result would be evidence that digitized signals encode information more reliably?

Accepted Answer

The digitized readings arrive as the exact numbers sent, while the analog voltages arrive shifted by varying amounts.

Answer

The digitized readings arrive a few milliseconds sooner than the analog voltages, so the office display updates earlier.

Answer

Both sets of readings arrive shifted by the same small amount.

Answer

The analog voltages change more smoothly than the digitized readings, which jump in steps.

Question 4

A station broadcasts the same music on an analog channel and a digital channel during a thunderstorm. Which observation would best support the claim that digital encoding is more reliable?

Accepted Answer

The analog channel filled with bursts of static while the digital channel played the track unchanged.

Answer

The digital channel used less of the available broadcast band than the analog channel.

Answer

The digital channel sounded louder than the analog channel during the storm.

Answer

Both channels crackled with static whenever lightning struck nearby.

Question 5

A photographer claims digital images survive being sent on repeatedly, unlike photocopied prints. Which observation is the strongest evidence for that claim?

Accepted Answer

After twenty sendings, the digital file's stored values were identical to the original, while the twentieth photocopy was blotchy and faint.

Answer

After one sending, the digital file and the first photocopy both looked almost the same as the original.

Answer

The digital file could be sent twenty times in less time than it took to make one photocopy.

Answer

The digital file looked sharper on a screen than the original print did.

Question 6

Look at the table of errors counted in each generation of copy. Which statement about the data supports the claim that digital copies are more reliable?

Accepted Answer

Analog errors climb with each generation while digital errors stay at zero through the tenth copy.

Answer

Both the analog and the digital error counts climb from one generation of copy to the next, but the analog count climbs faster.

Answer

Digital errors begin to climb only after the fifth copy.

Answer

Analog errors stay constant while digital errors fall toward zero.

Question 7

Engineers want to test whether a digitized control signal is more reliable than an analog one in a noisy factory. Which measurement would be the strongest evidence?

Accepted Answer

The number of commands the machine carries out incorrectly over a week with each signal type.

Answer

The strength of each signal as it leaves the controller.

Answer

The time each signal takes to travel from the controller to the machine.

Answer

The number of commands sent over a week with each signal type.

Question 8

On a long cable, small random noise is added to both signals. The digitized message is read back with no errors, while the analog one arrives distorted. Which reasoning best explains that difference?

Accepted Answer

Each part of the digitized signal is read as one of a fixed set of values, so noise smaller than the gap between values is discarded.

Answer

The digitized signal travels faster along the cable than the analog one, so the noise picked up on the way has less time to build up on it.

Answer

The digitized signal has a larger amplitude, so the added noise is a smaller fraction of it.

Answer

Noise added to a digitized signal cancels itself out over a cable this long.

Question 9

A tenth-generation analog copy hisses, while a tenth-generation digital copy matches the original exactly. Which reasoning links that evidence to the claim that digital encoding is more reliable?

Accepted Answer

Each digital copy rewrites the same fixed values, so small errors are not carried forward, while analog copying reproduces added noise as part of the signal.

Answer

Digital copying uses newer, better-built machines, which make fewer mistakes than the older analog machines that recording studios once used.

Answer

Digital files are smaller, so there is less of the signal for noise to damage.

Answer

Digital copies are made faster, leaving less time for noise to enter the signal.

Question 10

A digitized signal weakened over 40 km of cable is decoded correctly after a repeater rebuilds it. Which reasoning best explains why rebuilding works for a digital signal but not an analog one?

Accepted Answer

The repeater only has to decide whether each part is high or low before sending out a clean signal, while an analog repeater amplifies the noise along with the signal.

Answer

The repeater adds extra energy to the line, and that added energy pushes the noise off the cable ahead of the signal so that only the signal arrives.

Answer

The digital signal is carried at a frequency that electrical noise cannot reach.

Answer

The digital signal is shorter, so the repeater has less of it to correct.

Question 11

A sensor sends temperature as a smoothly varying voltage. Noise shifts that voltage slightly on the way. Which reasoning explains why the receiver cannot tell the noise from the reading?

Accepted Answer

Every voltage in the range stands for some temperature, so a shifted voltage still looks like a legitimate reading.

Answer

The receiver rounds each voltage to the nearest whole degree, so any shift smaller than one degree is hidden from the reading.

Answer

The noise always adds the same amount, so every reading is shifted by an equal step.

Answer

The voltage is too small for any receiver to measure accurately.

Question 12

A class argues that digital signals are better because music sounds louder through their digital speaker. Which correction should they make to that reasoning?

Accepted Answer

Loudness describes amplitude, not accuracy; the claim needs evidence about errors in the message after it is transmitted.

Answer

Loudness shows the signal carries more energy, and a signal that carries more energy is what the word reliability means.

Answer

Loudness shows the digital signal lost less of its information along the way.

Answer

Loudness is good evidence, because a louder signal always overpowers the noise around it.

Question 13

A message is sent as a stream of high and low voltages. How does the receiving computer turn that stream back into the letters of the message?

Accepted Answer

It reads each group of highs and lows as a code pattern that stands for one letter

Answer

It measures the exact voltage of each pulse, and each voltage stands for a different letter

Answer

It smooths the stream into a wave whose shape traces out each letter

Answer

It counts how many pulses arrive each second and turns that rate into a letter

Question 14

A class notices that a digital radio and an analog radio both fail at the far edge of the station's coverage. Which reasoning correctly limits the reliability claim?

Accepted Answer

Digital encoding resists small added noise, but it cannot rebuild a signal too weak to be read at all.

Answer

The claim is wrong, because an analog radio signal never fades with distance.

Answer

Digital signals must be more reliable everywhere, so the class must have misread what happened.

Answer

The failure shows that noise has no effect on either kind of signal.

Question 15

A weather station 12 km from its office sends readings along a cable beside a railway that adds random electrical noise. Which encoding better protects the readings, and why?

Accepted Answer

A stream of pulses read as high or low, because a random voltage that does not bridge the gap between high and low leaves the reading unchanged.

Answer

A smoothly varying voltage, because it carries every small change in temperature all the way to the office without leaving anything out.

Answer

A stream of pulses, because pulses travel along a cable faster than a varying voltage does.

Answer

A smoothly varying voltage, because random noise averages itself out over a distance this long.

Question 16

A hospital must send a patient's heart trace 40 km to a specialist through cabling shared with elevator motors. Which system better protects the trace, and why?

Accepted Answer

Numbered samples the receiver reads as fixed values, because interference below the step between two values still decodes to the same number.

Answer

A continuously varying voltage, because it keeps every detail of the trace with no gaps left out.

Answer

A continuously varying voltage, because motor noise disturbs numbers that have been stored as pulses but leaves a voltage untouched.

Answer

Numbered samples, because numbers lose less energy than voltages as they travel along cable.

Question 17

A space probe 200 million km away sends pictures on a faint radio signal that picks up noise. Which encoding gives the clearest picture on Earth, and why?

Accepted Answer

Digitized brightness values, because the receiver chooses between set values, so small noise does not alter what it reads.

Answer

A smoothly varying radio signal, because it carries a shade for every brightness the camera saw.

Answer

Digitized brightness values, because digital signals travel through space faster than analog signals.

Answer

A smoothly varying radio signal, because noise picked up in space cancels out over such a long journey.

Question 18

A library must keep recorded interviews usable for 50 years, recopying them whenever equipment changes. Which storage choice better protects the recordings, and why?

Accepted Answer

Digitized files, because each recopy reproduces the same fixed values instead of adding noise to the sound.

Answer

Magnetic tape, because tape keeps the smooth original sound with no values left out.

Answer

Digitized files, because files can be searched and labeled more easily than boxes of tape.

Answer

Magnetic tape, because the hiss added by copying stays quieter than the recording itself.

Question 19

A traffic control center sends light timings 6 km along a duct beside heavy power cables. Which method better protects the timings, and why?

Accepted Answer

Coded pulses the receiver reads as high or low, because a small added voltage still falls on the same side of the threshold.

Answer

A varying voltage, because the lights need one continuous instruction to follow rather than a set of separate pulses.

Answer

Coded pulses, because pulses use less electricity than a varying voltage does.

Answer

A varying voltage, because interference from power cables disturbs only pulsed signals.

Question 20

A school fire alarm panel must send its signal 400 m through a building full of electric motors. Which encoding should the engineers choose, and why?

Accepted Answer

A two-level pulse signal, because the panel only has to tell high from low, so interference that stays inside that gap changes nothing.

Answer

A varying voltage, because it can show how strong the alarm signal is as well as showing whether the alarm is on or off.

Answer

A varying voltage, because motor noise builds up faster on a pulsed signal than on a varying one.

Answer

A two-level pulse signal, because pulses carry more energy than a varying voltage does.

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Digital and Analog Signals

Ways to Play

Device Games: Students play on their phones

Blast Go

Zombie Escape

Avalanche

Maze Blast

Cave Climb

Blast Out

Mystery Auction

Tour Guide

Food Truck Rush

Tug of War

Alien Blast

Glacier Rush

Board Games: Teacher-led, projected to the class

Like what you see?

Bug Blast

BlastRace

BlastQuiz

BlastBoard

Seek & Destroy

Mystery Blast

Checkers

Texas Hold 'Em

Da Bomb

Castle Siege

Hot Potato

Market Mayhem

King of the Hill

Bank Heist

Top Corner

Digital and Analog Signals

Ways to Play

Device Games: Students play on their phones

Blast Go

Zombie Escape

Avalanche

Maze Blast

Cave Climb

Blast Out

Mystery Auction

Tour Guide

Food Truck Rush

Tug of War

Alien Blast

Glacier Rush

Board Games: Teacher-led, projected to the class

Like what you see?

More like this

Bug Blast

BlastRace

BlastQuiz

BlastBoard

Seek & Destroy

Mystery Blast

Checkers

Texas Hold 'Em

Da Bomb

Castle Siege

Hot Potato

Market Mayhem

King of the Hill

Bank Heist

Top Corner