Deck 16: Data Communication Fundamentals

Question 1

In Non Return to Zero encoding schemes,the signal or voltage level does not return to 0v (zero volts).One of the problems with this type of encoding is that

A)it does not work well with serial communications.
B)it is designed primarily for high speed communications only.
C)the signal ground of the transmitter is often different from that of the receiver
D)it works only for analog signals.
E)it is sometimes difficult to synchronize the timing of the transmitter and the receiver.

Answer 1

E

Question 2

In modern communication systems,data is sent from one point to another via

A)input data.
B)alternating current (A/C).
C)pressure changes.
D)electromagnetic signals.
E)direct current (D/C).

Answer 2

D

Question 3

An encoding scheme is used

A)in digital transmission to map binary digits to signal elements.
B)in analog transmission to clean up the quality of the transmission.
C)to help minimize errors.
D)A,B,and C.
E)A and B only.

Answer 3

D

Question 4

Asynchronous transmission includes a start and stop bit with each character transmitted to ensure

A)that the total number of bits is a factor of 10.
B)to allow a continuous stream of data.
C)to prevent single bit errors from occurring.
D)to allow the receiver to maintain synchronization with the sender.
E)to allow variable length encoding schemes.

Question 5

Analog encoding of digital information modulates a wave known as the
carrier in terms of its phase,frequency or amplitude.

Question 6

Standards are important when devices must communicate together.The four characteristics governed by these standards are

A)mechanical,electrical,functional,and procedural.
B)electrical,physical,functional,and signaling.
C)fundamental,mechanical,procedural,and protocol.
D)protocol,fundamental,physical,and signaling.
E)physical,virtual,electrical,and functional.

Question 7

One of the main differences between amplifiers and repeaters is that

A)amplifiers forward noise as well as data.
B)amplifiers clean the signal and then forward it.
C)amplifiers increase the amount of attenuation.
D)amplifiers focus primarily on digital signals.
E)amplifiers focus primarily on analog signals.

Question 8

Except for digital cellular telephones,copper wire is required for digital transmission.

Question 9

Synchronous serial transmissions are frame based,require the use of a preamble and are more efficient than asynchronous serial transmissions.

Question 10

It is difficult to use low frequencies for unguided radio transmission of data because the antenna dishes would have to be extremely large.

Question 11

A carrier wave is modulated with 4 amplitudes and 4 phase changes.How many bits can be represented with each signal change?

A)1
B)2
C)3
D)4
E)5

Question 12

For amplitude,frequency or phase shift keying,that respective characteristic of the carrier wave is changed to indicate the next binary digit.These binary digits can be represented by this signal change or a lack of signal change.

Question 13

Analog signals are

A)continuous.
B)discrete.
C)discontinuous.
D)Both A and B.
E)Both B and C.

Question 14

The efficiency of an asynchronous transmission using 1 stop bit,1 start bit and 1 parity bit is

A)20 %.
B)30 %.
C)50 %.
D)70 %.
E)80 %.

Question 15

A carrier wave is modulated with 4 amplitudes and 4 phase changes.How many possible signal combinations are there?

A)4
B)8
C)16
D)32
E)64

Question 16

Analog signals are less susceptible to noise interference and are more prone to attenuation than digital signals

Question 17

Digital signals are

A)continuous.
B)discrete.
C)discontinuous.
D)Both A and B.
E)Both B and C.

Question 18

Identify each of the following as either analog or digital signals.Use A if analog and D if digital.
Whales
Human voice
Computer bus communication
Cellular telephones
Satellite transmission
T-1 circuits

Question 19

In order to compensate for synchronization problems,another type of encoding method called biphase can be employed.These methods place a clock pulse within the data stream.

Question 20

Each signal change or element is called a

A)bit.
B)byte.
C)baud.
D)signal.
E)digit.

Question 21

Parity checking for error detection is most reliable for checking communications using high data rates.

Question 22

An error detecting scheme that employs a unique prime number is called

A)parity checking.
B)frame sequence checking.
C)error checking and error correcting.
D)cyclic redundancy check.
E)synchronous redundancy check.

Question 23

Error detection requires that extra bits be introduced into the data stream.