Analog and Digital

Question 1

What gets sent on a network?

Answer 1

 Information.
 Voice, pictures (facsimile), data (computer files), video, music.
 Information may be analog or digital.
 To be transmitted, information must be encoded.

Question 2

Analog Transmission

Answer 2

an analog waveform (or signal) is characterized by being continuously variable along amplitude and frequency.

Question 3

voice-grade line

Answer 3

analog circuit

-the human voice for example, can typically generate frequencies from 100Hz to 10,000Hz

Question 4

Analog Characteristics

Answer 4

• limited bandwidth, which means they can not support high-speed data
• analog is that noise accumulated as the signal traverses the network

Question 5

Digital Transmission

Answer 5

• signal is much simpler than analog
• rather than being a continuously variable waveform, it is a series of discrete pulses, representing one bits and zero its

Question 6

Collating sequence

Answer 6

coding scheme

• defines what combinations of ones and zeros constitute all the characters in a character set
• e.g. lowercase letters, uppercase letters, punctuation marks, digits, keyboard control functions

Question 7

Analog Characteristics

Signal

Answer 7

Continuously variable, in both amplitude and frequency

Question 8

Analog Characteristics

Capacity measurement

Answer 8

Hz

-e.g., a telephone channel is 4KHz

Question 9

Analog Characteristics

Bandwidth

Answer 9

Low bandwidth (4KHz), which means low data transmission rates (up to 33.6Kbps) because of limited channel bandwidth

Question 10

Analog Characteristics

Network capacity

Answer 10

Low; one conversation per telephone channel

Question 11

Analog Characteristics

Network manageability

Answer 11

Poor; a lot of labor is needed for network maintenance and control because dumb analog devices do not prvide management information streams that allow the devive to be remotely managed

Question 12

Analog Characteristics

Signal Structure

Answer 12

High; the signal contains a wide range of frequencies and amplitudes

Question 13

Analog Characteristics

Security

Answer 13

Poor;when you tap into an analog circuit, you hear the voice stream in its native form, and it is difficult to detect an intrusion

Question 14

Analog Characteristics

Error rates

Answer 14

High; 10-5bits (i.e., 1 in 100,000 bits) is guaranteed to have an error

Question 15

Digital Characteristics

Signal

Answer 15

Discrete signal, represented as either changes in voltage or changes in light levels

Question 16

Digital Characteristics

Capacity measurement

Answer 16

Bits per second (e.g., a T-1 line carries 1.544Mbps, and an E-1 line transports 2.048Mbps)

Question 17

Digital Characteristics

Bandwidth

Answer 17

High bandwidth that can support high-speed data applications that involve video and multimedia

Question 18

Digital Characteristics

Network capacity

Answer 18

High; multiplexers enable multiple conversations to share a communications channel and hense to achieve greater transmission efficiencies

Question 19

Digital Characteristics

Network manageability

Answer 19

Good; smart devices produce alterts, alarms, traffic statistics, and performance measurements, and technicians at a network control center (NCC) or network operations center (NOC) can remotely monitor and mangage the varios network elements

Question 20

Digital Characteristics

Signal Structure

Answer 20

Low; only two discrete signals-the one and the zero-need to be transmitted

Question 21

Digital Characteristics

Security

Answer 21

Good; encryption can be used

Question 22

Digital Characteristics

Error rates

Answer 22

Low; with twisted-pair, 10-7 bits (i.e., 1 in 10 million bits) has an error; with satellite, 10-9 bits (i.e., 1 in 1billion bits) has an error, and with fiber, 10-11 bits(i.e., 1 in 100 billion bits) to 10-13 bits (i.e., 1 in 10 trillion bits) has an error

Question 23

codec

Answer 23

• a contraction of coder-decoder
• converts analog signals into digital signals
• there are different codes for different purposes