3.5 - Digital Transmission of Analog Data

Question 1

Analog voice data can be sent over digital networks using _____________

Answer 1

digital transmission

Question 2

A pair of special devices called ________ (code/decode, or coder/decoder) is used in the same way that a pair of modems is used to translate the data to send across the circuit

Answer 2

codecs

Question 3

A _________ is attached to the source of the signal (e.g., a telephone or the local loop at the end office) and translates the incoming analog voice signal into a digital signal (coding)

Answer 3

codec

Question 4

A second codec at the receiver’s end translates the digital data back into analog data (________)

Answer 4

decoding

Question 5

The __________ signal is only a rough approximation of the original signal

Answer 5

digitized

Question 6

The difference between the original signal and the digitized signal is called _____________

Answer 6

quantizing error

Question 7

There are two ways to reduce quantizing error:

Answer 7

1. Increase the number of amplitude levels
2. Sample more frequently

Question 8

__________ bits (or 128 levels) reproduces human speech adequately

Answer 8

7

Question 9

Music-quality audio typically uses ________ bits (65,536 levels)

Answer 9

16

Question 10

Sampling more frequently than the usual is called _____________

Answer 10

oversampling

Question 11

The North American telephone network uses _____________ (PCM)

Answer 11

pulse code modulation

Question 12

With PCM, the input signal is sampled _________ times per second

Answer 12

8,000

Question 13

_________________________ (ADPCM) is the alternative used by IM and many other applications that provide voice services over lower-speed digital circuits

Answer 13

Adaptive differential pulse code modulation

Question 14

_____________ (VoIP) is commonly used to transmit phone conversations over digital networks

Answer 14

Voice over Internet Protocol