問題一覧
1
Amplitude Modulation suffers from ________
Cross Modulation
2
The ability of receivers to select the wanted signals among various incoming signal is called ________
Selectivity
3
In TV transmission, picture signal is ________ modulated.
VSB
4
The analog signal needs to be sampled at a minimum sampling rate of:
2fs
5
If the height of the reflecting layer of the ionosphere increases, the skip distance of a high frequency (HF) transmission:
becomes greater
6
Radio waves that arrive at a receiving site along different paths can cause signal fading if these waves have different _____.
phase relationships
7
In a frequency modulation receiver, the _______ is located between the limiter and the audio frequency amplifier.
frequency discriminator
8
What does horizontal wave polarization mean?
The electric lines of force of a radio wave are parallel to the earth`s surface
9
In digital transmission, what modulation technique requires minimum bandwidth?
Delta modulation
10
The error probability of a PCM is:
All of the choices
11
What kind of emission would your FM transmitter produce if its microphone failed to work?
An unmodulated carrier
12
In a low-level AM system, amplifiers following the modulated stage must be:
linear devices
13
How little electrical current flowing through the human body can be fatal?
As little as 20 milliamperes
14
Reception of high frequency (HF) radio waves beyond 4000 km is generally possible by _____ wave.
ionospheric
15
What may happen if an SSB transmitter is operated with the microphone gain set too high?
It may cause splatter interference to other stations operating near its frequency
16
Consider the same noiseless channel of 3000 Hz bandwidth transmitting a signal with four signal levels (for each level, we send 2 bits). Calculate the maximum bit rate.
12 kbps
17
A digital signal has eight levels. How many bits are needed per level?
3
18
A one-to-all communication between one source and all hosts on a network is classified as a _______ communication.
broadcast
19
We have a low-pass channel with bandwidth 100 kHz. What is the maximum bit rate of this channel?
200 kbps
20
A router is a connecting device that operates in the _______ layer(s).
physical, data-link, and network
21
A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network?
2 Mbps
22
Which of the following restrictions apply to analog broadcasting?
Interference, fading and multipath reception
23
When propagation speed is multiplied by propagation time, we get the ________.
distance a signal or bit has traveled
24
Assume that we need to download text documents at the rate of 100 pages per minute. A page is an average of 24 lines with 80 characters in each line and each character requires 8 bits. Then the required bit rate of the channel is _____.
25.6 kbps
25
What factor significantly affects the frequency of occurrence of the sporadic-E layer?
Latitude
26
We need to send 265 kbps over a noiseless channel with a bandwidth of 20 kHz. How many signal levels do we need?
98.7 levels
27
A signal travels through an amplifier, and its power is increased 10 times. Calculate the amplification or gain of power.
10 dB
28
If we transmit a signal, the frequency of which is so high we no longer receive a reflection from the ionosphere, the signal frequency is above the:
maximum usable frequency
29
The signal-to-noise ratio is often given in decibels. Assume that SNR = 36 dB and the channel bandwidth is 2 MHz. Calculate the theoretical channel capacity.
24 Mbps
30
Consider an extremely noisy channel in which the value of the signal-to-noise ratio is almost zero. In other words, the noise is so strong that the signal is faint. Calculate the channel capacity.
0
31
The power of a signal is 10 mW and the power of the noise is 1 µW. What are the values of SNR and SNR_dB?
40 dB
32
Consider a noiseless channel with a bandwidth of 3000 Hz, transmitting a signal with two signal levels. What is the maximum bit rate?
6 kbps
33
If link transmits 4000 frames per second and each slot has 8 bits, the transmission rate of circuit of this TDM is ______.
32 kbps
34
The greatest amount of absorption takes place in the ionosphere under which of the following conditions?
When the density of the ionized layer is the greatest.
35
Two or more strong out-of-band signals mix in your receiver to produce interference on a desired frequency. What is this called?
Intermodulation interference
36
Radio communications can be diffracted to exceptionally long distances through the use of what frequency band at what relative power level?
Very low frequency; High power
37
Radio waves above the MUF will experience what effect when refracted from the ionosphere?
They will overshoot the desired location
38
The effectiveness of a data communications system depends on what four fundamental characteristics?
Delivery, accuracy, timeliness, and jitter
39
A parity-check code can detect an ____ number of errors.
odd
40
What is the process of adding one extra byte whenever there is a flag or escape character in the text?
Byte stuffing
41
For transmission over bodies of water, _______ polarization is much better for antennas at the lower heights.
vertical
42
In the reflection of waves, if the reflecting surface is smooth and polished, the angle between the incident ray and the normal will be ______ the angle between the reflected ray and the normal.
the same as
43
What is the most common UTP connector, which is a keyed connector, meaning the connector can be inserted in only one way?
RJ45
44
Substances that transmit almost all the light waves that fall upon them are said to be ______.
transparent
45
What signals can be used for short-range communication in a closed area using line-of-sight propagation?
Infrared
46
The first service provided by the data-link layer is ______.
framing
47
In ____ propagation, higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) where they are reflected back to earth.
sky
48
In _____ TDM, the data rate of the link is n times faster, and the unit duration is n times shorter.
synchronous
49
In wave propagation, the reflected energy is the greatest when the wave is _____ to the reflecting surface.
nearly parallel
50
Consider the same noiseless channel of 3000 Hz bandwidth transmitting a signal with four signal levels (for each level, we send 2 bits). Calculate the maximum bit rate.
12 kbps
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100問 • 1年前問題一覧
1
Amplitude Modulation suffers from ________
Cross Modulation
2
The ability of receivers to select the wanted signals among various incoming signal is called ________
Selectivity
3
In TV transmission, picture signal is ________ modulated.
VSB
4
The analog signal needs to be sampled at a minimum sampling rate of:
2fs
5
If the height of the reflecting layer of the ionosphere increases, the skip distance of a high frequency (HF) transmission:
becomes greater
6
Radio waves that arrive at a receiving site along different paths can cause signal fading if these waves have different _____.
phase relationships
7
In a frequency modulation receiver, the _______ is located between the limiter and the audio frequency amplifier.
frequency discriminator
8
What does horizontal wave polarization mean?
The electric lines of force of a radio wave are parallel to the earth`s surface
9
In digital transmission, what modulation technique requires minimum bandwidth?
Delta modulation
10
The error probability of a PCM is:
All of the choices
11
What kind of emission would your FM transmitter produce if its microphone failed to work?
An unmodulated carrier
12
In a low-level AM system, amplifiers following the modulated stage must be:
linear devices
13
How little electrical current flowing through the human body can be fatal?
As little as 20 milliamperes
14
Reception of high frequency (HF) radio waves beyond 4000 km is generally possible by _____ wave.
ionospheric
15
What may happen if an SSB transmitter is operated with the microphone gain set too high?
It may cause splatter interference to other stations operating near its frequency
16
Consider the same noiseless channel of 3000 Hz bandwidth transmitting a signal with four signal levels (for each level, we send 2 bits). Calculate the maximum bit rate.
12 kbps
17
A digital signal has eight levels. How many bits are needed per level?
3
18
A one-to-all communication between one source and all hosts on a network is classified as a _______ communication.
broadcast
19
We have a low-pass channel with bandwidth 100 kHz. What is the maximum bit rate of this channel?
200 kbps
20
A router is a connecting device that operates in the _______ layer(s).
physical, data-link, and network
21
A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network?
2 Mbps
22
Which of the following restrictions apply to analog broadcasting?
Interference, fading and multipath reception
23
When propagation speed is multiplied by propagation time, we get the ________.
distance a signal or bit has traveled
24
Assume that we need to download text documents at the rate of 100 pages per minute. A page is an average of 24 lines with 80 characters in each line and each character requires 8 bits. Then the required bit rate of the channel is _____.
25.6 kbps
25
What factor significantly affects the frequency of occurrence of the sporadic-E layer?
Latitude
26
We need to send 265 kbps over a noiseless channel with a bandwidth of 20 kHz. How many signal levels do we need?
98.7 levels
27
A signal travels through an amplifier, and its power is increased 10 times. Calculate the amplification or gain of power.
10 dB
28
If we transmit a signal, the frequency of which is so high we no longer receive a reflection from the ionosphere, the signal frequency is above the:
maximum usable frequency
29
The signal-to-noise ratio is often given in decibels. Assume that SNR = 36 dB and the channel bandwidth is 2 MHz. Calculate the theoretical channel capacity.
24 Mbps
30
Consider an extremely noisy channel in which the value of the signal-to-noise ratio is almost zero. In other words, the noise is so strong that the signal is faint. Calculate the channel capacity.
0
31
The power of a signal is 10 mW and the power of the noise is 1 µW. What are the values of SNR and SNR_dB?
40 dB
32
Consider a noiseless channel with a bandwidth of 3000 Hz, transmitting a signal with two signal levels. What is the maximum bit rate?
6 kbps
33
If link transmits 4000 frames per second and each slot has 8 bits, the transmission rate of circuit of this TDM is ______.
32 kbps
34
The greatest amount of absorption takes place in the ionosphere under which of the following conditions?
When the density of the ionized layer is the greatest.
35
Two or more strong out-of-band signals mix in your receiver to produce interference on a desired frequency. What is this called?
Intermodulation interference
36
Radio communications can be diffracted to exceptionally long distances through the use of what frequency band at what relative power level?
Very low frequency; High power
37
Radio waves above the MUF will experience what effect when refracted from the ionosphere?
They will overshoot the desired location
38
The effectiveness of a data communications system depends on what four fundamental characteristics?
Delivery, accuracy, timeliness, and jitter
39
A parity-check code can detect an ____ number of errors.
odd
40
What is the process of adding one extra byte whenever there is a flag or escape character in the text?
Byte stuffing
41
For transmission over bodies of water, _______ polarization is much better for antennas at the lower heights.
vertical
42
In the reflection of waves, if the reflecting surface is smooth and polished, the angle between the incident ray and the normal will be ______ the angle between the reflected ray and the normal.
the same as
43
What is the most common UTP connector, which is a keyed connector, meaning the connector can be inserted in only one way?
RJ45
44
Substances that transmit almost all the light waves that fall upon them are said to be ______.
transparent
45
What signals can be used for short-range communication in a closed area using line-of-sight propagation?
Infrared
46
The first service provided by the data-link layer is ______.
framing
47
In ____ propagation, higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) where they are reflected back to earth.
sky
48
In _____ TDM, the data rate of the link is n times faster, and the unit duration is n times shorter.
synchronous
49
In wave propagation, the reflected energy is the greatest when the wave is _____ to the reflecting surface.
nearly parallel
50
Consider the same noiseless channel of 3000 Hz bandwidth transmitting a signal with four signal levels (for each level, we send 2 bits). Calculate the maximum bit rate.
12 kbps