which is not an example of data communications

8/10/2019 Which is Not an Example of Data Communications

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Which is not an example of data communications?

a. a teletype printing news bulletins

b. a computer transmitting files to another computer

c. an automatic teller machine checking account balances with

banks computer

d. a salesman telephoning orders to the office

Two-state (binary) communications systems are better because

a. they can interface directly with the analog telephone network

b. the components are simpler, less costly, and more reliable

c. people think better in binary

d. interstate calls are less costly

Which is not a positional notation system?

a. Roman (MCMXXXVII)

b. Binary (01111110)

c. Decimal (1492)

d. Hexadecimal (3A2B)

The Baudot code

a. was invented by the Baudot brothers, Mark and Space

b. requires the scape character to print numbers

c. requires shift characters to provide sufficient combinations

d. was invented by Emiles sister, Bridgette

The standard ASCII

a. is version II of the ASC standard

b. has 128 characters, including 32 control characters

c. is a subset of the 8-bit EBCDIC code

Extended ASCII

a. adds extra digits to standard ASCII

b. provides 128 additional character definitions beyond standard ASCIIc. doubles the bit length of each ASCII character

d. provides extra characters that you define

Escape sequences

a. use the ESC character to indicate the start of a special control

sequence

b. are used to switch (escape) between ASCII and EBCDIC codes

c. are a popular daydream for inmates

d. all of the choices

The principal difference between batch processing and on-line processing is

a. computer resources are used more efficiently for on-line

processing

b. teleprinters are used for batch processing; CRTs are used for

on-line processing

c. transactions are grouped for batch processing; transactions are

processed as needed for on-line processing

d. none of the choicesd. is used only in the U.S. and Canada

Impact printers

a. strike a ribbon against the paper to produce character images

b. include ink-jet and thermal devices

c. are rapidly becoming obsolete

d. either B or C

Glass teletypes

a. are among the most recent developments in CRT terminals

b. were so-named because they had the same interface with fiber-

optic transmission systems

c. are teleprinters designed to interface with fiber-optic transmission

systems


Electromechanical teleprinters

a. use a complex mechanical buffer to match speed between

transmitting and receiving machine

b. use start/stop codes to synchronize sending and receiving

equipment

c. are rarely used today

d. either B or C

ASCII terminals are generally defined as

a. terminals using synchronous transmission in EBCDIC

b. terminals using synchronous transmission in ASCII

c. terminals using asynchronous transmission in ASCII

d. any terminal having an American (dollar-sign) keyboard

The difference between timing and framing is

a. timing is concerned with the individual bits; framing is concerned

with the boundaries between characters.

b. timing refers to serial transmission; framing refers to parallel

c. timing is concerned primarily with the asynchronous systems;

framing is concerned with asynchronous systemsd. none of the choices

Escape codes are so called because

a. in effect, they provide a means to temporarily escape from the

standard meanings of the character set

b. they initiate operation of the escapement mechanism in

teleprinters

c. they cause cursors to escape from the CRT screen and roam aroud

in memory

d. it is easier to use

The QWERTY keyboard

a. is still considered to be the layout allowing the greatest typing

speed

b. is the most popular keyboard, but not necessarily the best

c. is the key layout that is rarely used

d. none of the choices

Memory-mapped displaysa. are associated with electromechanical teleprinters

b. have the advantage that they do not take up memory space

c. allow direct addressing of display locations by the processor


Serial printers

a. are used to transmit gain prices

b. are faster than CRT terminals and offer more flexibility

c. print one character at a time


Non-impact printers

a. are normally quieter than impact printers

b. generate carbon copies easily

c. produce fully-formed characters

d. works fast and no error

CRT terminals

a. are the most widely-used hardcopy terminals

b. offer high-speed display and formatting flexibility

c. do not utilize microprocessors

d. are asynchronous device

User-programmable terminals

a. are replacing personal and professional computers

b. offer more flexibility at lower cost

c. are being replaced by personal and professional computers

d. gives better output

Ergonomics

a. involves the interface between people and machines, such as

terminals

b. is the application of ergonomics to communication

c. utilizes three-level ergo-coding for transmission over certain

channels

d. much cheaperSerial and parallel transmission

a. differ in how many bits are transferred per character

b. are used in synchronous and asynchronous systems, respectively

c. differ in whether the bits are on separate wires or all on one

d. either A or C

Memory-mapped displays

a. are utilized for high-resolution graphics, such as maps

b. use ordinary memory to store the display data in character form

c. store the display data as individual bits

d. video

Asynchronous transmission

a. is less efficient that synchronous, but simpler

b. is much faster that synchronous transmission

c. is another name for isochronous transmission

d. either A or B

Single-buffering

a. is more efficient than double-buffering

b. is less efficient than no buffering

c. provides very little time to upload the incoming character from

the register


Most terminal keyboard

a. provide numerous additional specialized keys

b. are strictly typewriter-style, with few extra keys

c. use the Dvorak layout


The amount of uncertainty in a system of symbols is also called

a. bandwidth

b. loss

c. entropy

d. quantumRedundancy measures

a. transmission rate of a system

b. how likely symbols are to be repeated

c. time between failure

d. system cost

An example of a bounded medium is

a. coaxial cable

b. waveguide

c. fiber optic cable


Loading refers to the addition of

a. resistors

b. capacitors

c. bullets

d. inductance

Coaxial cable has no inductors witha. the same diameter

b. a common axis

c. equal distance


Fiber optic cables operates at frequencies near

a. 20 MHz

b. 200 MHz

c. 2 GHz

d. 800 THz

HF radio waves follow how many basic paths on leaving the transmitter?

a. two

b. four

c. one

d. many

The area of coverage of a satellite radio beam is called its

a. bandwidth

b. circular polarization

c. footprint

d. identity


2/3

Transmission of binary signals

a. less bandwidth than analog

b. more bandwidth than analog

c. the same bandwidth than analog

d. a license from the FAA

The standard first-level digital multiplex system in the U.S. operates at

a. 2.048 Mbps

b. 44.736 Mbps

c. 1.544 Mbps

d. 9600 bps

Flow control is

a. what people do who open and close the floodgates on dam

b. the process whereby the modem matches the rate of the receiver

c. the process of starting and stopping the terminal output to avoid

loss of characters by the receiving device

d. either A or C

Buffering is

a. the process of temporarily storing data to allow for small

variations in device speed

b. a method of reducing the severity of communications headaches

c. storage of data within the transmitting modem until the receiver is

ready to receive


Direct machine-to-machine transmission over long distances without modem is

not practical because

a. copper wire does not transmit DC efficiently

b. a DC path that will handle data in pulse from does not existc. data comes from the computer in the form of tones, not pulses

d. it is very expensive

Modulation is the

a. varying of some parameter of a carrier, such as its amplitude to

transmit information

b. utilization of single transmission channel to carry multiple signals

c. transmission of pulses in DC from over a copper wire

d. either A or B

RS-232, RS-449, RS-530, V.24 and X.21 are examples of

a. standards for various types of transmission channels

b. standard for interfaces between terminals and modems

c. standard for interfaces between modems and transmission

facilities

d. standard for end-to-end performance of data communications

system

RTS/CTSa. is the way the modem indicates ringing, and the way terminal

indicates it is ready for the call to be answered

b. is the way DTE indicates that it is ready to transmit data , and the

way DCE indicated that it is ready to accept data

c. are the pins that represent received transmissions and carrieir

transmissions


Pin 7, the Signal Ground

a. completes the circuit for control and data signals

b. indicates a failure in the ground side of the transmission line

c. completes the circuit for control signals but not data signals

d. either a or b

Pin 22, the Ring Indicator

a. must be present on all modems connected to the switched

network b. is used on acoustic-coupled modems but not on direct-connect

types

c. is asserted when ringing voltage is present on the line

d. either B or C

The reason that many cables have RS-232 connectors with some wires

crossed or connected to each other is

a. there are various RS-232 standard

b. many computers and peripherals use RS-232 serial interfaces but

not as DTE-to-DCE

c. asynchronous modems reverse the direction of transmitted and

received from data from the standard


What is one principle difference between synchronous and asynchronous

transmission?

a. the bandwidth required is different

b. the pulse heights are differentc. the clocking is mixed with the data in asynchronous transmission

d. the clocking is derived from the data in synchronous

transmission

Synchronous modems cost more than asynchronous modems because

a. they are larger

b. they must contain clock recovery circuits

c. the production volume is larger

d. they must operate on larger bandwidth

The scrambler in a synchronous modem is in the

a. control section

b. receiver section

c. transmitter section

d. terminal section

Binary codes are sometimes transformed in modems into

a. Hexadecimal

b. Huffman codes

c. Gray code

d. Complementary codes

The digital-to-analog converter in a synchronous modem sends signals to the

a. modulator

b. transmission line

c. terminal

d. equalizer

The receive equalizer in asynchronous modem is called

a. a compromise equalizer

b. a statistical equalizer

c. an adaptive equalizer

d. an impairment equalizer

The receive equalizer reduces delay distortion using a

a. Tapped delay line

b. Difference engine

c. Descrambler

d. Gearshift

A Western Electric 201 modem operates with a carrier frequency of

a. 1000 Hz

b. 1200 Hz

c. 1600 Hz

d. 1800 Hz

The CCITT V.26 modem has a modulation rate of

a. 1200 Hz

b. 1200 bauds

c. 1560 cps


The transmission signal coding method for T1 carrier is called

a. Binary

b. NRZc. Bipolar

d. Manchester

Multiplexing is

a. the process of increasing bandwidth on a channel

b. a technique that enables more than one data source to share the

use of a common line

c. mailing letters at the Post Office

d. the ability to share frequency by time

One of the reasons frequency division multiplexing has essentially been

replaced by time division multiplexing is because

a. there is more time than frequency

b. it is difficult to place channels side by side

c. noise is amplified with voice

d. mist available frequencies have been used

When the amplitude pulse is varies to represent analog information the method

is calleda. PCM

b. PWM

c. PAM

d. PPM

The PCM sampling rate is 8000 samples per second because

a. that represents the maximum rate technology supports

b. this rate allows unique values

c. this rate allows the faithful reconstruction of an analog signal

d. this rate is easily produced by a sampling chip

In general digital transmission provides higher level of signal quality than analog

transmission because

a. repeaters regenerate digital pulses and remove distortion while

amplifier increase an analog signal

b. digital signals are smaller than analog signals and cannot be easily

distorted c. analog signals are continuous and are not easily distorted

d. digitals signals are easier to sample analog signals

The D4 framing pattern contains a sequence of

a. 24 bits

b. 4 terminals and 8 framing bits

c. 8 terminals and 4 framing bits

d. 12 bits

Bipolar signaling is used in place of unipolar signalling on T1 lines because

a. bipolar produces twice as many marks as unipolar signal

b. it allows transmission at polar loactions

c. bipolar signaling reduces residual DC voltage build-up allowing a

digital signal to be separated from power through the use of transformer

d. it allows transformers to be spaced far from one another which

reduces the cost of transmission

B7 Zero Code Suppression is technique which

a. allows data to flow on a digital lineb. ensures each byte has at least one mark bit

c. is the largest clear channel encoding technique developed by Bell

Laboratories

d. provides a clear channel transmission capability allowing-kbps

data transmission on a voice channel

Intentional bipolar violations

a. represent coding errors caused by line impairments

b. are used to convey information or maintain a minimum number

of ones on a digital line

c. result in successive marks having opposite polarities

d. only occur in the laboratory

Demultiplexing by a time division multiplexer occurs based on

a. the position of data within a frame

b. the position of a frame within a group of names

c. the activity of a connected device

d. the priority assigned to a connected deviceThe requirements for a successful transmission system using light are

a. powerful, reliable light source

b. strong glass

c. reliable, low-cost transmission medium

d. both A and C


3/3

The core of an optical fiber has

a. a lower index of refraction than air

b. a lower index of refraction than the cladding

c. a higher index of refraction than cladding


For single-mode fibers, the core diameter is about

a. 10 times the fiber radius

b. 3 times the wavelength of the light carried in the fiber

c. 15 micrometers

d. 10 times the wavelength of the light carried in the fiber

Over a period of 30 years, a kilometre of fiber optic cable is likely to be broken

a. not at all

b. once

c. 10 times

d. 2 or 3 times

Deposition of dopants on fiber preforms is done by

a. outside vapor deposition

b. axial vapour deposition

c. inside vapour deposition


A light-emitting diode is able to couple how much power into an optical fiber?

a. 10 watts

b. 10 milliwatts

c. 100 microwatts

d. 1 picowatt

Avalanche photodiode receivers can detect bits of transmitted data by receiving

a. 1 photonb. 10 photons

c. 100 photons

d. 200 photons

One unsolved problem with satellite system is

a. coverage

b. privacy

c. bandwidth

d. access

The AT&T FT3C fiber optic transmission system is designed to use how many

light wavelengths?

a. one

b. two

c. three

d. ten

The SL Undersea Lightguide system can carry how many two-way voice

channels?a. 10,000

b. 100,000

c. 35,000

d. 760

When the index of refraction is greater in Material 1 than it is Material 2, the

velocity of propagation in Material 1 compared to Material 2 is

a. equal to or greater

b. greater

c. lesser

d. equal

The different angles of entry of light into an optical fiber where the diameter of

the core is many times the wavelength of the light transmitted is called

a. emitters

b. modes

c. sensorsd. refractors

In single-mode fibers, a large fraction of the power is propagated in the

a. shealth

b. core

c. cladding

d. air

The loss in signal power as light travels down a fiber is called

a. propagation

b. scattering

c. absorption

d. attenuation

The coupling efficiency of an LED light source to an optical fiber with a

numerical aperture of 0.2 or more is

a. 60%

b. 10%

c. 2%d. 0.1%

which is not an example of data communications

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