30 Questions
What type of data takes on continuous values?
Analog data
What is a characteristic of a periodic signal?
It completes a pattern within a measurable time frame
What type of signal can have an infinite number of values in a range?
Analog signal
What is a simple periodic analog signal?
A sine wave
What type of data is typically used in data communications?
Only digital data
What is a characteristic of a nonperiodic signal?
It changes without exhibiting a pattern or cycle
What is the frequency of a signal that does not change at all?
Zero
What is the phase of a sine wave that is offset 1/6 cycle with respect to time 0?
60°
What is represented by a single spike in the frequency domain?
A single-frequency sine wave
What is the result of decomposing a non-periodic composite signal using Fourier analysis?
A combination of sine waves with continuous frequencies
What is the bandwidth of a composite signal?
The difference between the highest and the lowest frequencies
Why is a single-frequency sine wave not useful in data communications?
Because it is not suitable for transmitting complex information
What is the bandwidth of a periodic signal composed of five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz?
800 Hz
What are the lowest and highest frequencies of a nonperiodic composite signal with a bandwidth of 200 kHz and a middle frequency of 140 kHz?
40 kHz and 240 kHz
How many bits are needed to represent each level of a digital signal with eight levels?
3 bits
What is the minimum number of signal levels required for a digital signal to transmit 2 bits of information per level?
8 levels
How many bits are needed to represent each level of a digital signal with nine levels?
3.17 bits
What is the main difference between analog and digital signals?
Analog signals have a continuous range of values, while digital signals have discrete levels
What is the name of the converter that changes digital signals to analog signals and vice versa?
Modem
What is signal impairment caused by?
The imperfection of transmission media
What happens to the signal as it travels through a transmission medium?
It changes its form or shape
What is attenuation?
A loss of energy or reduction of amplitude
What is the effect of a 3 dB loss on a signal's power?
It reduces the power by half
What happens to the signal's power if it is increased 10 times after passing through an amplifier?
It becomes 10 times stronger
Why do engineers use decibels to measure changes in signal strength?
Because decibel numbers can be added or subtracted when measuring several points
What is thermal noise caused by?
The random motion of electrons in a wire
What is the unit of measurement for the loss in a cable?
Decibels per kilometer
What happens to the signal power when traveling through a cable with a loss of -0.3 dB/km?
It decreases by 0.3 dB/km
What is crosstalk?
The effect of one wire on another
What is the power of the signal at 5 km if the signal at the beginning of a cable has a power of 2 mW and a loss of -0.3 dB/km?
Less than 2 mW
This quiz covers the transformation of data into electromagnetic signals, analog and digital data, and their characteristics. Learn about continuous and discrete values, and the differences between analog and digital data.
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