Deck 5: Data Communication Fundamentals

Question 1

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

Answer 1

D

Question 2

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

Answer 2

True

Question 3

One of the least common error-detecting codes is the cyclic redundancy check.

Answer 3

False

Question 4

Analog signals are:

A)continuous
B)discrete
C)discontinuous
D)all of the above

Question 5

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

Question 6

Undetected and uncorrected errors can degrade performance and response times in any system that handles large volumes of data.

Question 7

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 8

Both analog and digital information can be encoded as either analog or digital signals.

Question 9

The simplest approach to error detection is to append a parity bit to the end of a block of data.

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

For sizable blocks of data,asynchronous transmission is far more efficient than synchronous.

Question 15

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

Question 16

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

Question 17

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

Question 18

Digital signals are:

A)continuous
B)discrete
C)discontinuous
D)none of the above

Question 19

When no character is being transmitted,the line between transmitter and receiver is in an idle state.

Question 20

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)all of the above

Question 21

Converting digital data to analog signals involves the use of a _________.

Question 22

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

Question 23

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

Question 24

_________ data take on continuous values on some interval; for example,voice and video are continuously varying patterns of intensity.

Question 25

An _________ is a continuously varying electromagnetic wave that may be transmitted over both guided and unguided media.

Question 26

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

Question 27

In _________ the phase of the carrier signal is shifted to encode data.

A)PSK
B)FSK
C)ASK
D)BFSK

Question 28

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%

Question 29

A _________ is a sequence of voltage pulses that may be transmitted over a wired medium; for example,a constant positive voltage may represent binary 0,and a constant negative value may represent binary 1.

Question 30

________ is concerned with the content of the signal.

A)Digital transmission
B)Analog transmission
C)Digital signaling
D)Analog signaling

Question 31

In an operation very similar to that performed by a modem,analog data can be represented by a digital signal; the device that performs this function is a ________.

Question 32

Each signal change or element is called a:

A)bit
B)byte
C)baud
D)signal

Question 33

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

Question 34

________ data take on discrete values; examples are text,integers,and binary data.

Question 35

If 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

Question 36

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

Question 37

________ are electric or electromagnetic representations of data.

Question 38

The mapping from binary digits to signal elements is the ________ scheme.

Question 39

__________ is the communication of data across a computer network by the propagation and processing of signals.

Question 40

_________ is the physical propagation of the signal along a communication medium.

Question 41

The process of error control involves two elements: error detection and _________.

Question 42

The _________ is the most widely publicized of a family of modern technologies designed to provide high-speed digital data transmission over ordinary telephone wire.

Question 43

With ________ transmission,a block of bits is transmitted in a steady stream without start and stop codes.

Question 44

The data plus preamble,postamble,and control information are called a _________.

Question 45

A _______ modem permits Internet access over cable television networks.