Chapter 3

Question 1

What is the difference between a point-to-point and a multipoint circuit?

Answer 1

Point-to-point connects two devices directly; multipoint connects multiple devices on one shared circuit.

Question 2

What are the three types of data flows?

Answer 2

Simplex (one-way), half-duplex (two-way, one at a time), full-duplex (two-way, simultaneous).

Question 3

Name three types of guided media.

Answer 3

Twisted pair wire, coaxial cable, and fiber optic cable.

Question 4

Describe how twisted pair wire works.

Answer 4

Consists of pairs of wires twisted together to reduce electromagnetic interference.

Question 5

What is coaxial cable?

Answer 5

Cable with a copper core and shielded outer layer; low error rates and less interference.

Question 6

What is fiber optic cable?

Answer 6

Transmits data using light through strands of glass or plastic; high speed and low interference.

Question 7

Name four types of wireless media.

Answer 7

Radio, infrared, microwave, satellite.

Question 8

What is analog data?

Answer 8

Continuously varying data like sound waves.

Question 9

What is digital data?

Answer 9

Data represented in binary form (0s and 1s).

Question 10

What is the difference between analog and digital transmission?

Answer 10

Analog transmission sends continuous signals; digital transmission sends binary data.

Question 11

Why are telephone circuits now mostly digital?

Answer 11

Digital transmission has fewer errors, higher speeds, better security, and is more efficient and cheaper.

Question 12

What is coding in data communication?

Answer 12

Representing symbols (letters, numbers) using binary patterns.

Question 13

What are three major coding schemes?

Answer 13

ASCII, EBCDIC, Unicode.

Question 14

How does parallel data transmission work?

Answer 14

All bits in a data unit are sent simultaneously over multiple wires.

Question 15

How does serial data transmission work?

Answer 15

Bits are sent one at a time sequentially over a single wire.

Question 16

What is the difference between unipolar and bipolar signaling?

Answer 16

Unipolar uses one voltage level; bipolar alternates voltages for binary values.

Question 17

What is Manchester encoding?

Answer 17

A signal transition occurs in the middle of each bit; improves error detection.

Question 18

Name three characteristics of sound waves.

Answer 18

Amplitude (volume), frequency (pitch), and phase (wave start point).

Question 19

What is bandwidth?

Answer 19

The range of frequencies a circuit can carry; measured in Hz.

Question 20

What is the usable bandwidth of a traditional telephone line?

Answer 20

300 to 3300 Hz (3000 Hz total).

Question 21

What is amplitude modulation (AM)?

Answer 21

Changing wave height to represent binary data.

Question 22

What is frequency modulation (FM)?

Answer 22

Changing wave frequency to represent binary data.

Question 23

What is phase modulation (PM)?

Answer 23

Changing wave starting point (phase) to represent binary data.

Question 24

Can modulation techniques be combined?

Answer 24

Yes, combining amplitude, frequency, and phase allows more bits per symbol.

Question 25

Is bit rate the same as symbol rate?

Answer 25

Only when one bit per symbol is used; otherwise, bit rate = symbol rate × bits per symbol.

Question 26

What is a modem?

Answer 26

A device that modulates and demodulates digital and analog signals.

Question 27

What is QAM (Quadrature Amplitude Modulation)?

Answer 27

Combines amplitude and phase variations to represent multiple bits per symbol.

Question 28

What is 64-QAM?

Answer 28

A QAM variant that sends 6 bits per symbol.

Question 29

What affects transmission speed?

Answer 29

Bits per sample and samples per second.

Question 30

What is oversampling?

Answer 30

Sampling more than twice the highest frequency to improve signal quality.

Question 31

Why is data compression important?

Answer 31

It increases data throughput by reducing the size of transmitted data.

Question 32

What standard uses Lempel-Ziv compression?

Answer 32

V.42bis; it builds a dictionary of repeating patterns to compress data.

Question 33

How does Pulse Code Modulation (PCM) work?

Answer 33

Samples analog voice 8000 times/sec and converts it to 8-bit binary numbers.

Question 34

What is quantizing error?

Answer 34

Difference between original analog signal and digitized version; causes distortion.

Question 35

What is multiplexing?

Answer 35

Combining multiple signals to transmit over one circuit.

Question 36

Why is multiplexing used?

Answer 36

It maximizes circuit usage by allowing simultaneous transmissions.

Question 37

How does DSL work?

Answer 37

Uses existing telephone lines with devices at both ends to support high-speed data.

Question 38

What is Frequency Division Multiplexing (FDM)?

Answer 38

Divides circuit into separate frequency bands; each channel uses a different frequency.

Question 39

What is Time Division Multiplexing (TDM)?

Answer 39

Divides circuit by time; each device takes turns to send data.

Question 40

What is Statistical TDM (STDM)?

Answer 40

Similar to TDM, but dynamically assigns time slots based on usage.

Question 41

What is Wavelength Division Multiplexing (WDM)?

Answer 41

Uses multiple light wavelengths (colors) over fiber optics to carry multiple signals.

Question 42

What is inverse multiplexing (IMUX)?

Answer 42

Combines several low-speed links into one high-speed connection.

Question 43

Why choose TDM over FDM when buying a multiplexer?

Answer 43

TDM is faster, more efficient, and easier to maintain.

Question 44

Are traditional modems obsolete?

Answer 44

Mostly, but they’re still useful for low-bandwidth needs or specific legacy systems.

Question 45

What is the maximum data rate of a 4000 Hz analog circuit using QAM?

Answer 45

16,000 bps (4 bits × 4000 symbols).

Question 46

What is the max data rate of a 10 MHz circuit using 64-QAM and V.44?

Answer 46

Up to 360 Mbps with compression.

Question 47

What is the capacity of a 10 MHz circuit using Manchester encoding?

Answer 47

10 Mbps (1 bit per symbol).

Question 48

What is the symbol rate of a 100 Mbps circuit using bipolar NRZ?

Answer 48

100 MHz (1 bit per symbol).

Question 49

What is VoIP?

Answer 49

Voice over IP transmits voice as digital packets using codecs over the Internet.