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TDMM Flash Cards > Ch 1 - P 1 - Digital Signals > Flashcards

Ch 1 - P 1 - Digital Signals Flashcards

1
Q

What is the most significant property of a digital signal?

A

The most significant property of a digital signal is that at any time it can take on only a value from a discrete set of values.

TDMM: Page 1-29

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2
Q

What 3 steps are used to convert an analog signal to a digital signal?

A
  1. Filtering
  2. Sampling
    #. Quantizing / companding
    TDMM: Page 1 - 29
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3
Q

Why is the analog filtered before it is sampled?

A

To limit its frequency content

TDMM: Page 1-29

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4
Q

What sampling rate is used to faithfully reproduce the analog signal during the conversion process?

A

A rate that is at least twice the highest frequency component of the analog signal

TDMM: Page 1-29

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5
Q

What is quantizing?

A

Assigning each sampled value a discrete level that approximates the analog signal at the sampling instant

TDMM: Page 1-30

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6
Q

What is companding?

A

Non-uniform mapping between the analog sampled value to an assigned digital level

TDMM: Page 1-30

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7
Q

Name the 2 forms of companding that are in current use.

A
  1. A-Law
  2. Mu-Law

TDMM: Page 1-30

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8
Q

What type of companding is used in the United States, Canada, and Japan?

A

Mu-Law

TDMM: Page 1-30

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9
Q

What type of companding is used in Europe?

A

A-Law

TDMM: Page 1-30

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10
Q

A-Law and Mu-Law are compatible.

A

False. Although they perform similar functions, A-Law and Mu-Law are not compatible.

TDMM: Page 1-30

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11
Q

What term is used to describe the three-step process for converting an analog signal into a digital signal?

A

Pulse code modulation (PCM)

TDMM: Page 1-30

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12
Q

What is used to encode speech signals at data rates lower than 64 kb/s?

A

Data signal processing

TDMM: Page 1-30

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13
Q

What data rates can be used by ADPCM?

A

40,32,24 and 16 kb/s

TDMM: Page 1-30

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14
Q

What device is used to convert speech to a digital signal and its subsequent decoding to speech?

A

Codec

TDMM: Page 1-30

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15
Q

At what rates can vocoders transmit speech?

A

8 to 2.4 kbs

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16
Q

What do lower bit rates typically imply about a signal’s quality?

A

That the signal quality is degraded

TDMM: Page 1-30

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17
Q

What process involves combining binary data from several different sources into a single composite bit stream?

A

Time Division Multiplexing (TDM)

TDMM: Page 1-31

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18
Q

What is the purpose of TDM?

A

To increase the information-carrying capacity of the digital telecommunications channel. TDMM: Page 1-31

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19
Q

How is TDM accomplished?

A

By predetermined (deterministic) interleaving of samples from different voice channels along with one or more bits for control purposes to make up a frame.

TDMM: Page 1-31

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20
Q

What is the most popular form of TDM?

A

Statistical TDM

TDMM: Page 1-31

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21
Q

In the DS1 format, the digital data from __ speech channels is combined for transmission over a single transmission channel.

A

In the DS1 format, the digital data from 24 speech channels is combined for transmission over a single transmission channel.

TDMM: Page 1-31

22
Q

What is the data rate for the DS1 format?

A

1.544 Mb/s

TDMM: Page 1-32

23
Q

Describe the CEPT PCM-30 format.

A

In the CEPT PCM-30 format, the digital data from 30 speech channels is combined for transmission over a single transmission channel.

TDMM: Page 1-32

24
Q

What is the data rate for CEPT PCM-30 format?

A

2.048 Mb/s

TDMM: Page 1-32

25
What term is used to describe the process of reconstituting the individual channels from the composite signal?
Demultiplexing TDMM: Page 1 - 32
26
What is a channel bank?
Multiplexing and demultiplexing equipment TDMM: Page 1-32
27
What stages of multiplexing contain A/D conversion?
Only the first order multiplexing stage (T1 and E1) TDMM: Page 1-32
28
In the United States, how many T1 frames are needed to create a superframe?
12 TDMM: Page 1-33
29
In Europe, how many E1 frames are needed to create a multiframe?
16 TDMM: Page 1-33
30
What is the basic unit of digital data?
Bit TDMM: Page 1-33
31
True or False -- A sequence of binary pulses consisting of 1s and 0s is the optimum format for transmitting digital data over balanced-twisted pair cables.
False. A sequence of binary pulses consisting of ones and zeros is not the optimum format for transmitting digital data over balanced twisted-pair cables. TDMM: Page 1-33
32
What is the final step in the encoding process?
The modification of the shape and pattern of pulses to achieve more efficient transmission TDMM: Page 1-33
33
What is the line-encoding technique designed to do?
Eliminate the DC component Improve timing recovery TDMM: Page 1-33
34
What encoding technique is used for T1 carriers?
Bipolar alternate mark inversion (AMI) TDMM: Page 1-33
35
What type of encoding allows signal transition to occur in the middle of every bit interval?
Manchester encoding TDMM: Page 1-33
36
What term is used to describe the rate at which a signal can change states?
Baud TDMM: Page 1-34
37
What transmission method is used for ISDN (basic rate)?
2B1Q TDMM: Page 1-35 Table 1.10
38
What transmission method is used for ISDN (primary rate)?
Bipolar TDMM: Page 1-35, Table 1.10
39
What transmission method is used for HDSL?
2B1Q TDMM: Page 1-35, Table 1.10
40
What transmission method is used for 10Base-T?
Manchester TDMM: Page 1-35, Table 1.10
41
What is the encoding rate for ISDN (basic rate)?
160 kb/s TDMM: Page 1-35, Table 1.10
42
What is the encoding rate for ISDN (primary rate)?
1.544 Mb/s TDMM: Page 1-35, Table 1.10
43
What is encoding rate for HDSL?
2 x 784 kb/s TDMM: Page 1-35, Table 1.10
44
What is the encoding rate for 10BASE-T?
10 Mb/s TDMM: Page 1-35, Table 1.10
45
What is a QAM signal?
A signal composed of two sinusoidal carriers, each having the same frequency but differing in phase by one quarter of a cycle TDMM: Page 1-37
46
Which QAM sinusoid is the equivalent of a sine wave?
I signal TDMM: Page 1-37
47
Which QAM sinusoid is the equivalent of a cosine wave?
Q signal TDMM: Page 1-37
48
What type of modulation does DMT use?
Multicarrier modulation TDMM: Page 1 -37
49
How can data rates be adjusted with DMT?
By increasing the number of sub-bands and by carrying the number of bits carried in each sub-band TDMM: Page 1-37
50
Which line application uses 8B/1Q4 PAM 5 encoding?
1000BASE-T TDMM: Page 1-37

TDMM Flash Cards (7 decks)

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