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Which two statements are true about analog to digital conversion of voice signals for use in digital telephony networks？（）
A . The three required steps in the analog to digital conversion are sampling，encoding，and compression.
B . The three required steps in the analog to digital conversion are sampling，quantization，and compression.
C . The three required steps in the analog to digital conversion are sampling，quantization，and encoding.
D . The output of the sampling process is a pulse code modulation （PCM） signal.
E . The output of the sampling process is a pulse amplitude modulation （PAM） signal.
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Which statement is true about the digital to analog conversion process？（）
A . the two steps of digital to analog conversion are decompression and reconstruction of the analog signal
B . the two steps of digital to analog conversion are decoding and filtering
C . the two steps of digital to analog conversion are decompression and filtering of the analog signal
D . the two steps of digital to analog conversion are quantization and decoding
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In a VoIP network， which type of interface would an analog fax machine connect to？（）
A . Type 1
B . Type 2
C . FXS
D . FXO
E . E&M
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Operational amplifiers, used primarily in analog circuits, are characterized by（）
A . high input impedance, high gain and low output impedance
B . high input impedance, high gain and high output impedance
C . low input impedance, low gain and high output impedance
D . low input impedance, high gain and low output impedance
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When analog signals are digitized using the G.711 codec， voice samples are encapsulated into protocol data units （PDUs） involving which three headers？ （）
A . IP
B . TCP
C . RTP
D . UDP
E . H323
F . CRTP
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What is the term that is used to describe the process of converting a signal from digital to analog？（）
A . packetization
B . quantization
C . decoding
D . sampling
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When a router converts analog signals to digital signals， what three steps are always included in the process？（）
A . involution
B . encoding
C . sampling
D . quantization
E . compression
F . companding
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analogy的含义是（）。
A . 登录号
B . 算法
C . 比对
D . 类推
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What are two steps that are taken when a router converts a voice signal from analog to digital form？（）
A . sampling
B . packetization
C . quantization
D . serializatio
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When a router converts analog signals to digital signals， what three steps are always included in the process？ （）
A . involution
B . encoding
C . sampling
D . quantization
E . compression
F . companding
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Analog signal and digital signal are two kinds of signals in the form of control.
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Which English proverb is analogous to the Chinese equivalent, “Nothing in the world is difficult for one who sets his mind to it”?
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Which one of the following items is NOT a main purpose of an analogy?
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Why does cognitive psychology consider the computer to be good analogy of the human brain?
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Analogies are especially helpful in explaining abstract ideas , for they relate ideas that cannot be experienced through the senses of sight, smell, hearing, touch, or taste, to a sense experience, thus making the ideas easy to understand.
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It is difficult to make an analogy _______ cars and airplane.
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What does the author mean by stating in line 7 that “this analogy is not far off the mark”？
A．The definition is not precise.
B．The discussion lacks necessary information.
C．The differences are probably significant.
D．The comparison is quite appropriate.
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What does the trip analogy suggest？
A．These mothers are doing more than what is necessary.
B．These parents care too much about the children
C．This may cause delayed growth of the children.
D．Parents may bring the same work ethic to parenting as they once did to their careers.
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According to Shannon's equation,what is the channel capacity of an analog voice-grade phon
According to Shannon's equation, what is the channel capacity of an analog voice-grade phone line with a bandwidth of 3100 Hz and a signal-to-noise ratio or 30 dB？
A．9.1 Kbps
B．9.3 Kbps
C．30.9 Kbps
D．30.17 Kbps
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In 1997, devotees of home electronics eagerly awaited the DVD player, a new device that could play movies without videotape, and with greater clarity. It caught on even faster than CD music players and within four years, DVD movies surpassed VHS tapes in sales. The DVD's success is just on example of a historic shift from analog to digital technologies. They began with computing and are now spreading to industries from banking to publishing. Products and services are shedding the limits of their physical form. to become encoded information that never degrades, can be reproduced perfectly and distributed around the world in minutes, or less.
Another example is photography: by the end of this year, tile number of images captured digitally each day is expected to surpass the number of images captured on film. With digital cameras and other devices linked to personal computers, we can collect vast amounts of data, which fortunately takes up little or no closet space. Today's average personal computer has a hard drive that can store 300 times more information than a decade ago. Technologies, such as broadband e-commerce, are expected to be the primary means of delivering entertainment and media by the end of this decade. Even life itself is increasingly digitized. The human genome(基因组), the recipe for our genetic makeup, has been mapped and encoded and researchers are harnessing the power of computing to accelerate the development, of new, lifesaving drugs.
The implications of this broad, digital revolution are enormous, although they tend to be over-shadowed by the struggles of high-tech industries to recover from the go-go years of the 1990s. Those struggles are real, yet there are reasons for optimism about a return to robust economic growth and job creation in the next several years. The digital innovations(创新) of the past two decades continue to bear fruit, so stay tuned for good news--digitally, of course.
Digital technologies really began to take form. when ______.
A．information was encoded
B．DVD technology was introduced
C．it was used with photography
D．used in computing
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analogous（）
A．相似的，类似的
B．值得纪念的，难忘的，值得注意的
C．质量的，定性的
D．高傲的，轻蔑的
E．断然拒绝，回绝，冷落
F．严谨，一丝不苟
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The first step to process an analog signal digitally is to（）
A．encode it by using the binary coding scheme
B．quantize it in amplitude
C．sample it at discrete time instant
D．pass it through a D/A converte
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A continuous signal is also called because its waveform is often analogous to that of the physical variable（）
A．an analog signal
B．a discrete signal
C．a digital signal
D．a sampled signal
