Digital signals and information

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수업 노트

Signals and Codes

Signals are used to transmit information, and codes have been used throughout history to keep messages secret.
Example: George Washington used codes to send secret messages during the American Revolutionary War.
Fireflies communicate using patterns of light signals—each blinking pattern is a unique signal.

A coded alphabet where each letter is represented by a unique symbol.

Analog Signals

Analog signals are representations of actual images, sounds, or words, often using waves to transfer information.
Analog signals do not use mathematical codes.
Examples: conversations (sound waves), film cameras (light waves), vinyl records (grooves in plastic).
Analog instruments like alcohol thermometers and grandfather clocks measure continuously.

A clock tower (Big Ben), an example of an analog instrument.

Digital Signals

Digital signals are sent as mathematically coded waves and can travel long distances.
They are decoded back into understandable information at the receiving end.
Examples: computers, smartphones, digital cameras, digital thermometers, video game systems.

Analog vs. Digital Recording

Analog recording captures every part of the sound wave, including background noise, making it complex and prone to errors.
Digital recording takes samples of the wave at set intervals, not the whole wave.
The diagram below shows the difference: the analog wave is smooth and continuous, while the digital wave is stepped because it only records samples.
Digital waves are simpler and easier to copy or transmit without mistakes because they are not affected by outside sources.

A diagram comparing an analog wave to digital waves sampled at low and high rates.

Sampling and Storage

Low sampling records less often; high sampling records more often; analog records constantly.
Digital stores only a smaller number of values compared to analog's infinite values, making it easier to remember/copy accurately.
Example: Digital thermometers show set values (98.6 to 98.7) while alcohol thermometers show every tiny change.
Analog requires more storage space and is more likely to store flaws; digital takes less space and filters out interference.

A digital thermometer and an analog thermometer

Reliability and Examples

Vinyl records (analog) hold about 44 minutes of music; CDs (digital) hold 75-80 minutes.
Digital files on devices can hold 100-150 songs on a CD, or about 14,000 songs on 64 GB storage.
Digital signals are more reliable for storing and transmitting information because they are less affected by damage or interference.
However, digital signals must be converted back to analog for humans to hear or see.

A vinyl record, CDs, and a smartphone with earbuds.

Conclusion

The structure of digital signals (sampled, coded) makes them more reliable than analog signals for storage and transmission.
Digital technology reduces issues like static and physical damage, as seen in electronic music devices vs. vinyl records.

슬라이드

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연습 문제

무료 미리 보기 — 37개 중 8개 문제. 가입하면 전부 볼 수 있어요.

1.Analog signals use mathematical codes to transfer information.
Easy
True or false?
2.Which of the following is an example of an analog signal?
Easy
- AVinyl record
- BDigital song file
- CSmartphone text message
- DMP3 player
3.Which of the following are advantages of digital signals compared to analog signals? (Select all that apply)
Medium
- AThey are easier to copy without mistakes.
- BThey are unaffected by outside sources.
- CThey store every tiny piece of information.
- DThey take up less storage space.
- EThey are more reliable for storing information.
4.Digital signals record every part of the sound wave.
Easy
True or false?
5.Why is a digital signal more reliable for storing information than an analog signal?
Medium
- AIt records every part of the wave.
- BIt is simpler, so it is easier to copy without mistakes.
- CIt uses more storage space.
- DIt is affected by background noise.
6.Which of the following are examples of digital signals? (Select all that apply)
Medium
- AA digital camera storing a photo
- BA vinyl record playing music
- CA smartphone receiving a text
- DA film camera imprinting an image on film
- EA video game system sending data to a controller
7.An alcohol thermometer is an example of a digital signal.
Easy
True or false?
8.A digital thermometer shows temperatures in whole degrees. Which of the following readings would NOT be possible on this thermometer?
Medium
- A24 °C
- B24.5 °C
- C25 °C
- D26 °C

더 많은 문제

9.A 64 GB phone can hold about 14,000 songs. Approximately how many songs can a 32 GB phone hold?
Medium
- A7,000 songs
- B14,000 songs
- C28,000 songs
- D56,000 songs
10.A student records a sound wave using both an analog and a digital recorder. Which statement best describes the difference in the recorded waves?
Medium
- AThe analog wave is smooth and rounded because it records constantly; the digital wave is stepped because it samples periodically.
- BThe digital wave is smooth and rounded because it records constantly; the analog wave is stepped because it samples periodically.
- CBoth waves are identical because they record the same sound.
- DThe analog wave has gaps because it samples; the digital wave is continuous.
11.A digital signal can be transmitted over long distances without losing its original information.
Easy
True or false?
12.A student wants to compare the reliability of storing a sound recording as an analog signal versus a digital signal. Which experimental setup would best demonstrate the difference in reliability?
Medium
- ARecord the same sound wave using an analog recorder and a digital recorder, then play both back and compare the sound quality.
- BRecord the same sound wave using an analog recorder and a digital recorder, then copy each recording multiple times and compare the copies to the original.
- CRecord two different sounds using an analog recorder and a digital recorder, then compare their file sizes.
- DRecord the same sound wave using an analog recorder and a digital recorder, then measure the amplitude of each recording.
13.A student recorded a sound wave digitally with low sampling and then with high sampling. Which of the following statements about the two digital recordings are correct? (Select all that apply)
Hard
- AThe high-sampling recording will have more samples per second than the low-sampling recording.
- BThe low-sampling recording will have a smoother wave when graphed.
- CThe high-sampling recording will likely require more storage space than the low-sampling recording.
- DThe low-sampling recording will capture every part of the sound wave.
- EThe high-sampling recording will be more similar to the original sound wave than the low-sampling recording.
14.A student observes that a vinyl record can hold 44 minutes of music, while a CD can hold 75–80 minutes. What is the main reason for this difference?
Medium
- ACDs use analog signals that are more compact.
- BVinyl records store every part of the sound wave, requiring more space.
- CCDs use higher quality sound than vinyl records.
- DVinyl records are made of plastic, which is less dense than the material in CDs.
15.Analog signals are representations of actual images, sounds, or words.
Easy
True or false?
16.Digital signals use mathematical codes to transfer information.
Easy
True or false?
17.A digital signal is more reliable for storing information than an analog signal because it only records samples of the information.
Easy
True or false?
18.Which of the following is an example of a digital signal?
Easy
- AA vinyl record playing music
- BA film camera capturing an image
- CA digital thermometer displaying 98.6°F
- DA grandfather clock measuring time
19.Which statement best describes the difference between an analog wave and a digital wave?
Easy
- AAn analog wave is smooth and rounded because it records constantly; a digital wave is stepped because it records only samples.
- BAn analog wave is stepped because it records only samples; a digital wave is smooth and rounded because it records constantly.
- CBoth waves are smooth and rounded because they record every part of the wave.
- DBoth waves are stepped because they record only samples.
20.To be able to hear a digital song, it must be converted back into an analog signal before being transmitted to your ears.
Medium
True or false?
21.Match each type of signal to its characteristic.
Easy
- Analog
- Digital
- Records every part of the wave
- Records only samples at set intervals
22.Match each example to the type of signal it represents.
Easy
- Conversation between people
- Digital thermometer
- Vinyl record
- Smartphone app
- Analog signal
- Digital signal
- Analog signal
- Digital signal
23.Put the steps of digital sound transmission in order: 1. Sound is sampled and converted to code. 2. Code is transmitted over wifi. 3. Electronic device converts code back to analog sound. 4. You hear the sound.
Medium
- Sound is sampled and converted to code
- Code is transmitted over wifi
- Electronic device converts code back to analog sound
- You hear the sound
24.Put the following steps in the correct order for playing a digital song stored on a phone through speakers.
Medium
- The phone converts the digital code back into an analog signal.
- The phone transmits the digital code over wifi to a speaker.
- The speaker receives the digital code.
- The speaker converts the digital code into sound waves.
25.Complete the sentence about how digital signals are transmitted.
Easy
Digital signals are sent as ____ waves, and once they arrive at a receiving station, they are ____ back into information you can understand.
26.What term describes signals that are representations of actual images, sounds, or words?
Easy
27.What is the process called when a digital device converts a digital code back into an analog signal for your ears?
Medium
28.What term is used to describe signals that are sent as mathematically coded waves?
Easy
29.What is the term for the process of taking samples of a sound wave at certain periods to record it digitally?
Easy
30.A digital thermometer displays temperatures in increments of 0.1 °F. If it reads 98.6 °F, what will be the next higher reading?
Medium
31.A digital thermometer displays temperatures in increments of 0.1 °F. If it reads 98.6 °F, what will be the next higher reading?
Medium
- A88.8 °F
- B118.5 °F
- C108.6 °F
- D98.7 °F
32.A digital audio file stores 44,100 samples per second. How many samples are stored in a 3-second recording?
Medium
33.A CD can hold up to 150 songs. If each song takes up the same amount of space, how many songs can be stored on 5 such CDs?
Medium
34.A vinyl record can store 44 minutes of songs. A digital CD can store up to 150 songs. If each song averages 3 minutes, how many more minutes of music can the CD store compared to the vinyl record?
Medium
35.Explain why a scratched vinyl record may produce static or skip, while a scratched CD may have issues reading, but a digital file on a phone is not damaged by scratching.
Medium
36.Explain why a digital signal is more reliable for storing information than an analog signal.
Medium
37.Describe an experiment you could carry out to compare the storage requirements of analog and digital recordings of the same sound.
Hard

복습 노트

## Digital Signals and Information ### Analog vs. Digital Signals - **Analog signal**: continuous values; can be any real number within a range. Noise always degrades it. - **Digital signal**: discrete values; at any time it takes one of a finite number of values. Noise immunity: small changes do not affect the signal state. ### Binary Signals - Most common digital signal: **binary** (two states: 0 and 1, or low and high). - Represented by two voltage bands: near ground (0) and near supply voltage (1). - Each binary digit is a **bit**. ### Advantages of Digital Signals - **Noise immunity**: electronic noise, if not too great, is ignored by circuitry. - **Data compression**: reduces bandwidth needed for audio/video. - **Reliability**: more reliable than analog for encoding and transmitting information. ### Key Concepts - **Discrete values**: only specific levels are valid; levels within a band represent the same state. - **Logic signal**: another name for binary signal. - **Clock signal**: a special digital signal that synchronizes circuits; triggers on rising or falling edge. ### Applications - Used in all digital electronics: computers, data transmission, audio/video. - Physical quantity can be voltage, current, light pulses, magnetization, etc. ### Summary Digital signals use discrete values (often two) to represent information, providing noise immunity and reliability over analog signals.

Digital signal: A signal that represents data as a sequence of discrete values; at any given time it can only take on one of a finite number of values.
Analog signal: A signal that represents continuous values; at any given time it represents a real number within an infinite set of values.
Binary signal: A digital signal with two possible valid values (0 and 1, or low and high), representing one binary digit (bit).
Noise immunity: The property of digital signals that allows them to ignore small changes in signal level due to electronic noise, unlike analog signals.
Bit: A binary digit; the basic unit of information in digital systems, representing either 0 or 1.
Clock signal: A special digital signal used to synchronize digital circuits; logic changes are triggered by its rising or falling edge.

플래시카드

What is a digital signal?

A digital signal represents data as a sequence of discrete values, taking on only a finite number of values at any given time.

What is an analog signal?

An analog signal represents continuous values, taking on an infinite number of values within a range.

What is a binary signal?

A binary signal is a digital signal with only two possible valid values, typically 0 and 1 (or low and high).

What does 'bit' stand for?

Bit stands for binary digit, the basic unit of information in digital systems, representing a 0 or 1.

How are binary signals represented in electronics?

They are represented by two voltage bands: one near ground (0 volts) for 0, and one near the supply voltage for 1.

What is noise immunity?

Noise immunity is the ability of digital signals to ignore small changes in signal level, making them resistant to electronic noise.

Why are digital signals more reliable than analog signals?

Digital signals have noise immunity; small noise does not change the discrete value, whereas noise always degrades analog signals.

What is a logic signal?

A logic signal is another name for a binary signal, representing Boolean values (true/false or 0/1).

What is a clock signal?

A clock signal is a special digital signal that synchronizes digital circuits, with logic changes triggered by rising or falling edges.

What is the rising edge of a clock signal?

The rising edge is the transition from a low voltage to a high voltage.

What is the falling edge of a clock signal?

The falling edge is the transition from a high voltage to a low voltage.

What is a multivalued logic signal?

A multivalued logic signal has more than two discrete states, such as three-valued logic with three possible values.

What is pulse-code modulation (PCM)?

PCM is a method to digitally represent sampled analog signals by quantizing the amplitude into discrete levels.

What is data compression?

Data compression reduces the amount of data needed to represent information, often used in digital audio and video to decrease bandwidth.

How does a digital signal in communications handle noise?

Interference is minimized by filtering and using data redundancy, and digital signals have inherent noise immunity.

What is a bitstream?

A bitstream is a sequence of bits (0s and 1s) representing digital data, often transmitted as a digital signal.

What is the difference between baseband and passband transmission?

Baseband transmits digital signals directly as voltage pulses; passband modulates a carrier wave for long-distance or radio transmission.

What is a digital modulation scheme?

A digital modulation scheme encodes bits by varying a carrier wave's amplitude, frequency, or phase for passband transmission.

What is a line coding scheme?

A line coding scheme encodes bits into voltage levels for baseband transmission over wires.

Can a digital signal have more than two states?

Yes, multivalued logic signals have more than two states, but binary (two-state) signals are most common.

What physical quantities can represent a digital signal?

Digital signals can be represented by voltage, current, light intensity, phase, polarization, acoustic pressure, or magnetization.

What is the Boolean domain?

The Boolean domain consists of two values: false and true, often represented as 0 and 1 in digital circuits.

Why are digital signals used in computing?

Digital signals are reliable, noise-immune, and easy to process, making them ideal for computing and data transmission.

What does 'discrete' mean in the context of digital signals?

Discrete means the signal takes on only specific, separate values (e.g., 0 or 1) rather than a continuous range.

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