3.4 - Analog Transmission of Digital Data

Question 1

The telephone system (commonly called POTS for __________________) enables voice communication between any two telephones within its network

Answer 1

plain old telephone service

Question 2

This occurs when the signal sent over the transmission media continuously varies from one state to another in a wave-like pattern much like the human voice

Answer 2

Analog transmission

Question 3

These translate the digital binary data produced by computers into the analog signals required by voice transmission circuits

Answer 3

Modems (modulator-demodulator)

Question 4

One modem is used by the transmitter to produce the analog signals (____________) and a second by the receiver to translate the analog signals back into digital signals (_____________)

Answer 4

modulation…demodulation

Question 5

The sound waves transmitted through the voice circuit have three important characteristics:

Answer 5

1. Amplitude
2. Frequency
3. Phase

Question 6

The height of the wave is called _____________

Answer 6

amplitude

Question 7

Amplitude is measured in _____________.

Answer 7

decibels (dB)

Question 8

Every sound waves has two parts:

Answer 8

1. Half above the zero amplitude point (i.e., positive)
2. Half below (i.e., negative)

Question 9

The number of waves per second

Answer 9

Frequency

Question 10

Frequency is expressed in ________

Answer 10

hertz (Hz)

Question 11

Frequency is ___ cycle per second

Answer 11

1

Question 12

Frequency is the _________ of the length of the sound wave

Answer 12

inverse

Question 13

The direction in which the wave begins

Answer 13

Phase

Question 14

Phase is measured in the number of _____________

Answer 14

degrees

Question 15

We do this by transmitting a simple sound wave through the circuit (called the ____________) and then changing its shape in different ways to represent 1 or 0

Answer 15

carrier wave

Question 16

_____________ is the technical term used to refer to these “shape changes”

Answer 16

Modulation

Question 17

_____________ is the process of varying the electrical energy, specifically of the carrier wave, in the channel to transmit information

Answer 17

Modulation

Question 18

Three fundamental modulation techniques:

Answer 18

1. Amplitude modulation (AM)
2. Frequency modulation (FM)
3. Phase modulation

Question 19

With AM (also called ____________), the amplitude or height of the wave is changed

Answer 19

amplitude shift keying (ASK)

Question 20

AM is more susceptible to noise (more errors) during transmission than _____

Answer 20

FM

Question 21

FM (also called _______________), is a modulation technique whereby each 0 or 1 is represented by a number of waves per second (i.e., a different frequency)

Answer 21

frequency shift keying (FSK)

Question 22

With PM (also called _____________), one phase symbol is defined to be a 0 and the other phase symbol is defined to be a 1

Answer 22

phase shift keying (PSK)

Question 23

A _______ is a unit of information

Answer 23

bit

Question 24

A _______ is a unit of signaling speed used to indicate the number of times per second the signal on the communication circuit changes

Answer 24

baud

Question 25

ITU-T now recommends the term baud rate to be replaced by the term _____________

Answer 25

symbol rate