Deck 8: Digital Communications: Coding Techniques

Question 1

The amount of time it takes the hold capacitor in A/D system to reach its final value

A) sample time
B) acquisition time
C) aperture time
D) hold time

Answer 1

B

Question 2

Find the dynamic range of a PCM system of 16 bits

A) 48.16 dB
B) 24.08 dB
C) 12.04 dB
D) 96.32 dB

Answer 2

D

Question 3

Which coding is commonly used as Ethernet for local area networks?

A) RZ
B) NRZ
C) Multilevel binary codes
D) Manchester coding

Answer 3

D

Question 4

The rule that a signal sampled at a minimum of twice the rate of its highest significant frequency component can be fully reconstructed at the receiver with a high degree of accuracy is known as:

A) the Shannon-Hartley theorem
B) Nyquist criteria
C) the error algorithm
D) Barkenhausen criteria

Question 5

The varying amplitude values which are used in order to code an analog intelligence signal in a PCM system are called

A) compression levels
B) companding levels
C) quantizing levels
D) sample levels

Question 6

The number of bits required for a binary code to represent 305 different possibilities is

A) 8 bits
B) 2 bits
C) 9 bits
D) 3 bits

Question 7

Find the generating polynomial for a generating function of 1100111 for an 8-bit message

A) X^6 + X^4 + X^3 + X + 1
B) X^7 + X^4 + X^2 + 1
C) X^6 + X^5 + X^2 + X + 1
D) X^7 + X^5 + X^3 + 1

Question 8

An early alphanumeric 5-bit code that was developed in the days of teletype machines that has limited power is known as:

A) the Baudot code
B) EBCDIC
C) ASCII
D) the Gray code

Question 9

A popular serial data communication standard used on computers to connect to a mouse

A) RS-435
B) RS-232
C) IEEE-488
D) UART 16550A

Question 10

In which of the following is the sample signal voltage held constant between samples?

A) natural sampling
B) sample and hold
C) flat-top sampling
D) none of the above

Question 11

The time that the sample and hold circuit must hold the sampled voltage

A) sample time
B) acquisition time
C) hold time
D) aperture time

Question 12

The logical distance between defined states is called

A) Viterbi distance
B) binary distance
C) hamming distance
D) none of the above

Question 13

A single LSI integrated circuit that contains the A/D and D/A circuitry in a PCM system is known as:

A) a repeater
B) a time-division multiplexer
C) a codec
D) a quantizer

Question 14

Which of the following is a baseband type of signal?

A) PAM
B) RZ
C) PWM
D) PCM

Question 15

Which of the following is an application of PCM?

A) telephone systems
B) CD laser disks
C) digital audio recording
D) all of the above

Question 16

To achieve a dynamic range of 78 dB, how many bits will be used?

A) 10
B) 6
C) 13
D) 16

Question 17

The phenomenon associated with the generation of an erroneously created signal in the sampling process is called:

A) fold over distortion
B) aliasing
C) both A and B
D) none of the above

Question 18

Which of the following error detection schemes does not require retransmission of the data for correction to occur?

A) cyclic redundancy check
B) block check character
C) Hamming code
D) parity

Question 19

An alias signal is:

A) a signal that has a frequency equal to the difference between the applied analog frequency and the sampling frequency.
B) usually filtered out by anti-aliasing filters in PCM systems
C) a signal that forms in a PCM system that has failed to meet the Nyquist sampling rate
D) all of the above

Question 20

The type of PCM coding scheme that is popular in optical systems, satellite telemetry links, and magnetic recording systems is:

A) phase-encoded and delay modulation
B) RZ - return to zero
C) NRZ - non-return to zero
D) multilevel binary

Question 21

Given a (7,4) cyclic code, the length of the BCC is

A) 4
B) 3
C) 2
D) 1

Question 22

A non-recursive filter is an

A) algorithm that does not include previous output values to generate the current output
B) algorithm that includes the previous output values to generate the current output
C) algorithm that includes the previous and present output values to generate the current output
D) algorithm that includes the previous and present output values to generate the current output

Question 23

What is the order of a difference equation that requires three past input and output values?

A) second order
B) fourth order
C) third order
D) first order

Question 24

Reed-Solomon codes are

A) seldom used
B) also called CRC codes
C) forward error-correcting
D) none of the above

Question 25

The distance of a received code (00111) from a valid code of (00101);

A) 1
B) 3
C) 4
D) 2

Question 26

Given a (7,4) cyclic code, the length of the message is

A) 1
B) 3
C) 4
D) 2