1
Q
comprise both physical parts as well as the software required for
installing computer networks, both at organizations and at home.
A
Computer networks components
2
Q
are the server, client, peer, transmission medium, and connecting devices.
A
Hardware components
3
Q
are operating system and protocols
A
Software components
4
Q
-are high-configuration computers that manage the resources of the network. The network
operating system is typically installed in the server and so they give user accesses to the network resources.
-can be of various kinds: file servers, database servers, print servers etc
A
Servers
5
Q
are computers that request and receive service from the servers to access and use the
network resources.
A
Clients
6
Q
are computers that provide as well as receive services from other peers in a workgroup
network
A
Peers
7
Q
- are the channels through which data is transferred from one
device to another in a network. - may be guided media like coaxial cable, fibreoptic cables
etc; or maybe unguided media like microwaves, infra-red waves etc.
A
Transmission Media
8
Q
- act as middleware between networks or computers, by binding
the network media together.
A
Connecting Devices
9
Q
Common connecting devices:
A
a. Routers
b. Bridges
c. Hubs
d. Repeaters
e. Gateways
f. Switches
10
Q
is typically installed in the server and
facilitate workstations in a network to share files, database, applications, printers etc.
A
Network Operating Systems
11
Q
is a rule or guideline followed by each computer for data communication.
Protocol suite is a set of related protocols that are laid down for computer networks.
A
Protocol Suite
12
Q
two popular protocol suites are:
A
a. OSI Model ( Open System Interconnections)
b. TCP / IP Model
13
Q
any device capable of sending and/or receiving information over a communications channel,
providing communications interface functions
A
Terminals
14
Q
Basic Terminal components:
A
-Input mechanism
-Output mechanism
-Communications interface
15
Q
provides input capability in
most terminals.
A
Keyboard
16
Q
three types of keys
A
-Text Keys
-Control Keys
-Function Keys
17
Q
(what type of key?) A to Z, the numbers 0-9 and special characters
A
Text Keys
18
Q
(What key?) for the communication control codes, such as START, STOP, DELETE, and END OF
TRANSMISSION
A
Control Keys
19
Q
(what key?) include carriage return, backspace and horizontal tab. Some terminals contain
processing capability that enables the user to program special operations into auxiliary function keys (WWW
key which connects directly to internet).
A
Function Keys
20
Q
One function of the keyboard equipped terminal is to convert the character(s) indicated by the pressed key
into a ______ ___ _____ for transmission over a data link.
A
serial bit stream
21
Q
In a keyboard, Each character is represented by a code, generally
either _____or ______
A
ASCII, EBCDIC
22
Q
Which will have only number keys. It facilitates rapid entry of numeric data to the terminal or the
application may be dialing a number as in telephone handset
A
Numeric Pad
23
Q
It is a pen shaped I/O device used to touch the screen. The light activates the location where it was
touched. It can be used to write or sketch or erase certain lines on the video monitor of the computer. It is also
used for inputting graphics and reading bar codes.
A
Light pen
24
Q
-A special monitor that lets the user make choices by touching icons or graphical buttons on the
screen with fingers.
-these systems are used for interactive displays in museums and in automatic teller
machines
A
Touch screen
25
Hand held device used to point a cursor at a desired place on a computer screen; a
click instructs the computer to take some action.
Mouse
26
It is upside down mouse, which is common in laptop computers.
Track ball
27
-A piece of hardware for digitizing images.
-come in several versions, from
grayscale to color, and capable of scanning a variety of bit depths
Scanner
28
Varieties of scanners
* Flat bed scanner
* Sheet fed scanner
* Drum scanner
* Hand held scanner
* Card scanner
* 3D scanners (medical CAT scanners)
* Bar code scanner
29
gives the necessary information regarding a product to the customer as well as to the owner, such
as price, category, etc. It can give necessary information like inventory details, tax payments to the company
management
Bar code
30
When bar
code label is kept on the scanner, the laser beam inside the scanner touches the bars, the black bars absorb
the beam and the whites reflect the beam. A photo diode in the scanner converts the beam into electrical
pulses. These pulses are fed to the computer, which converts them into digital codes. These digital codes, in
turn, reach the main computer to give necessary information pertaining to the product
Bar code scanners
31
With digital cameras and digital camcorders direct digital entry is available for graphics
and full motion video
Direct digital entry
32
______ _____ ______ is becoming feasible. Many systems can recognize pretrainedwords if
spoken distinctly with pauses between words
Direct voice entry
33
Output device that uses striking action to make impressions on paper.
Impact printer
34
These printers print on character at a time.
e.g., Daisy wheel printer
Character printer
35
In these printers, a collection of dots forms each of the printed characters.
Therefore, there is no preset limit on the number or types of characters that can be printed. In NLQ (near letter
quality) mode each line is printed twice. The second printing is offset slightly so that it hides the individual dots
Dot matrix printer
36
A standard dot matrix printer uses ______ dots vertically and ______ horizontally
to produce a letter. The higher quality style of dot matrix printer uses 24 dots (or pins) vertically.
7 or 8 vertically, 5 to 8 horizontally
37
Output device that uses laser beams or streams of ink, rather than striking action, to
make images on paper
Non-impact printer
38
They use heat to transfer pigment from a
plastic ribbon to the paper.
Thermal wax transfer/ Dye sublimation printers
39
t is a non-impact printer that shoots fine streams of ink onto paper. The
inkjet or drop on demand technology works by changing the voltage pulses that command how nozzles
produce each drop of liquid. The nozzles contain piezoceramicelements that move when electricity is applied
to them. A positive voltage makes the nozzles contract and a negative voltage makes them expand. Each drop
is produced by contracting the nozzles which out the liquid. These are less expensive than laser printers,
but offer somewhat less resolution quality
Ink jet/Bubble jet printer
40
uses liquid ink.
Liquid inkjet
41
uses solid ink sticks
Solid inkjet
42
It is a non impact printer that uses laser beams to write information on photo sensitive
drums, over which paper and toner pass, making images on paper. Laser printers are high speed, high quality
devices which produce very high-resolution text and graphics, making them suitable for desk top publishing.
Laser printer
43
Output device that uses computer directed pens to create complex, high quality images.
Plotter
44
two types of plotters
1. Flat bed plotter
2. Drum plotter
45
(what plotter?)It moves a pen up and down across a flat drawing surface.
Flat bed plotter
46
(what plotter?)In this paper is fixed or supported on a drum and pen moves only from side to side.
Drum plotter
47
examples of plotters
-pen plotters
-electrostatic plotters
-dot matrix impact plotters
48
produce different colors by using multiple pens.
Multicolor plotters
49
Terminals that provide user with visual display of input and output.
Video display terminals
50
-It consists of cathode ray tube and its power supplies.
- consists of a glass vacuum
tube that contains one electron gun for a monochrome display, or three (red, green, and blue) electron guns
for a color display. Electron beams from these guns sweep rapidly a cross the inside of the screen from the
upper left to the bottom right of the screen.
CRT display
51
To stop the image from flickering, the beams sweep at a rate of between__________ times peer
second, depending on the phosphor persistence, and the scanning mode used is interlaced or non-interlaced.
This is known as refresh rate and is measured in Hz
43 and 87
52
A very narrow display that uses one of several technologies, such as
electroluminescence, LCD, or thin film transistors.
Flat panel display
53
uses electric current to align crystals in a special liquid. The rod shaped
crystals are contained between two parallel transparent electrodes, and when current is applied, they change
their orientation, creating a darker area.
-Many of them are also back-lit or side-lit to increase visibility and
reduce the possibility of eyestrain.
LCD display
54
uses a transistor to control every row of pixels on the screen. They are
slower to respond, have weaker colors, and have a narrower viewing angle, but they are cheaper than active
matrix screens
Passive matrix screen
55
uses an individual transistor to control every pixel on the screen. They have
high contrast, wide viewing angle, vivid colors, and fast screen refresh rates, and they do not show the
streaking or shadowing.
Active matrix screen
56
Plasma panels consist of two glass plates separated by a thin gap filled with a mixture of
argon and neon gas. Each plate has several parallel electrodes running across it. The electrodes on the two
plates run at right angles to each other. A voltage pulse applied between two electrodes, one on each plate,
causes a small segment of gas at the intersection of the two electrodes to glow. The glow of gas segments is
maintained by a lower voltage that is continuously applied to all electrodes. A similar pulsing arrangement can
be used to selectively turn points off
Plasma display
57
Some terminals have ______________, they are receive only devices.
no output mechanism
58
The capabilities of terminals can be enhanced by any of the following components:
-internal storage (buffer)
- processor
-auxillary storage
59
a small memory that holds a block of data while it is being transmitted, received, keyed in,
displayed, or otherwise manipulated. It can be used for output as well as input purposes
buffer
60
transmits the entire block of characters at its designed transmission speed over the
data link and then frees the data link for access by other users.
buffered terminal
61
(what terminal?)The _____________ gives a single character as output at a time
unbuffered terminal
62
It is an I/O device that incorporates processing capability such as text editing, character
checking, encoding/decoding, and communication handling within the terminal itself. It contains a little
computer, which may be a microprocessor or a minicomputer having some level of programmability.
-contains own processor; runs applications; PC is example; provides better line
utilization; communication software must run in the terminal
intelligent terminal
63
The level of intelligence of a terminal can be judged by the inclusion of special features like:
-Buffering
-Special editing function keys
-Paging/scrolling
-Cursor controls
-Format control
-Processing capabilities
-custom software programs
-automatic transmission of message blocks
64
Applications of intelligent terminals
* Data entry
* Inquiry/ response
* Transaction processing
* Message preparations/ text editing/ word processing
* Time sharing
* Remote batch processing
65
-It is normally a teleprinterand a video display terminal. It is cheaper than intelligent terminal.
-have no processing power; not addressable; cannot respond to polling messages; no
error detection; located near host computer
Dumb terminal
66
are characterized by their printing capability. These are usually
dumb terminals
Teleprinter terminals
67
The use of a PC as a terminal has the advantage of the
processing capability of the computer to provide additional capabilities.
PC terminals
68
_______________ of PC is very easy when compared to other terminals.
expandability and upgradability
69
A standalone information station that allows users to browse and retrieve
information
Kiosk
70
A terminal defined as a standard on a network that can handle diverse terminals. Signals to
and from each non standard terminal are converted to equivalent standard terminal signals by an interface
computer. The network protocols then operate as though all terminals were the standard virtual terminals.
Virtual terminal
71
is any type of specialized terminal configured to operate in a remote
location and to transmit and/or receive data from a host computer in batch form, usually over a voice grade
line. It is also called as remote batch terminal (RBT).
Remote Job Entry (RJE) terminals
72
characteristics of RJE
* It operates primarily in an online batch mode.
* It is generally configured to incorporate a computer.
* It can have a variety of peripheral devices, including high speed card readers and line
printers.
* It is used in remote locations with high volume input/output requirements.
* It can be intelligent and programmable to have communications processing as well as
data processing
73
are special purpose terminals devoted to a particular type of application
transaction terminals
74
They are primarily used in the retail environment and supermarkets for
recording data as sales are made. Some of them are capable of reading bar codes printed on the product
Point Of Sale (POS) terminals
75
They are transaction terminals used to read account, identifying information on the
magnetic strips (on credit cards) and are used to verify credit status
Credit/debit terminals
76
include automatic teller machines (ATMs), passbook reader/printers, magnetic ink
character recognition (MICR) equipment, and the like.
Banking terminals
77
where users can deposit or withdraw money, make
transfers between different bank accounts, and pay bills.
Automated Teller Machines (ATMs)
78
are designed to withstand severe conditions, such as vibration and heat.
They are usually configured as input devices.
Factory data collection terminals
79
is basically a telecopyingdevice that transmits/receive copy to/ from a remote
location
Facsimile (FAX) terminal
80
Application that converts and sends the white and black areas of a page over
telephone wires or wireless networks to a receiving machine that converts the coding back into white and
black areas and prints the message.
Facsimile (FAX)
81
Terminal device that does not share a controller with another terminal
Stand alone terminal
82
Terminal through which data can be entered by means of a typewriter like keyboard.
Keybroad terminal
83
Terminal specialized by hardware and/ or software to display graphics in
addition to text
Graphics terminal
84
Terminals that are in the same room or building may be configured in a cluster. Each stand alone terminal
device has its own controller, which manages its interface to communications lines. By clustering terminals, a
single cluster control unit (CCU) can serve the entire set of devices thereby lowering costs and improving line
utilization
Cluster control unit
85
The cluster control unit functions are:
* Line interface
* Buffering
* Error checking
* Message retransmission
* Local communication
* Format control
* Polling
86
-They allow several remote terminals at one site on a common multipoint circuit to share a single modem at
that site.
-do not multiplex; they simply provide a means of sharing the serial interface
of one modem among several terminals.
- enables transmission via polling and broadcasting. These devices are also called
as control units or cluster controllers.
Modem sharing devices
87
process of asking each device in a prearranged sequence if it has a message to send; if so,
the polling sequence is interrupted while that device is being serviced.
Polling
88
The addressed terminal turns the line around. If it has data, it sends the data to the controller
otherwise it puts a polling message addressed to its neighbor on the line.
Hub polling
89
They allow interconnection of terminals or microcomputers to host mainframe computers in many types of
configurations
Line adapters
90
enable terminal users to connect to more than one network and switch between
them, without plugging or unplugging any connector cables
Line interface modules
91
-It allows several incoming communication circuits to use a single port on a front end
processor. All front end processors have a fixed capacity of ports.
-may be used when
users want to exceed this designed capacity
Port sharing device
92
-are similar to port sharing devices except in the matter of location.
-are located at the remote end of the communication circuit, where as port sharing devices are at the central
site close to the host mainframe computer.
Line splitter
93
They allow two or more analog circuits to be shared as one. Bridges are not
multiplexers. They allow one modem to be used with circuits to more than one destination. Telephone
companies and users use bridges to create multipoint analog circuits from point to point segments.
Line bridging devices
94
They are used to connect two DTEs directly. They also are called null
modems
Modem eliminators
95
three types of terminals to be used on a network
1. Dumb terminals
2. Smart terminals
3. Intelligent terminals
4. Terminal emulation
96
nonprogrammable; addressable; data stored in buffer to transmit block mode; limited
processing capabilities
Smart terminals
97
can emulate any of the 3 terminal types
Terminal emulation
98
- collect data from multiple stations and
combine them into a single high-speed bit stream.
- provide end-to-end error checking and
correction, and circuit sharing.
- A device that combines data traffic from several low speed communication circuits onto a single high speed
circuit.
Multiplexers
99
Two types of multiplexers
1. Frequency division multiplexers
2. Time division Multiplexers
100
(what kind of multiplexer?) They can be used on multipoint circuits, but individual channels usually must each be for start stop data.
Frequency division multiplexers
101
Advantages of FDM
-robust
102
Disadvantages of FDM
-high production cost
-limited total capacity (2400 bps)
-usually requires a conditioned line
-most of them do not allow mixing of bit rates and sub-channels
-inflexible
103
* They can be used if all channels are point to point.
* Line capacity utilization is better than FDMs. They generally allow faster bit rates and potentially more
channels than FDM at less cost.
* They permit mixing of bit rates of the sub-channels.
Time Division Multiplexing (TDM)
104
-They assign each terminal a dedicated portion of the transmission capacity of the shared line.
-sends idle (masking) bits when a channel becomes inactive, they waste a lot of potential
capacity when the duty cycles are low.
-They should be used if the duty cycles (time sent filling time slots with actual data) of the data
channels to be multiplexed are relatively high. A high duty cycle means that the channel is actually carrying
bits most of the time
Classical TDMS (or dumb TDM)
105
A time division multiplexer (TDM) that dynamically allocates communication circuit time to each of
the various attached terminals, according to whether a terminal is active or inactive at a particular moment.
- Buffering and queuing functions are also included
- Whenever usage statistics show low duty cycles as the normal mode of utilization for most of the
channels to be multiplexed, a statistical multiplexer system is usually a good choice. These devices send only
data bits (no idle bits), so they can appear to have a higher total bit rate than the actual rate if high percentage
of idle bits are coming from the terminals.
Statistical TDMs (smart TDM)
106
-Each time slot is one bit long.
-Totally transparent to the terminals
(What kind of multiplexer?)
Bit interleaved multiplexer
107
- Each time slot is one byte long.
- The start-stop bits of the characters are stripped during multiplexing and again
reinserted after demultiplexing
(what kind of multiplexer?)
Byte-interleaved multpilexer
108
- is an advanced form of statistical time division multiplexer (STDM) that combines
voice, video and data transmission. It typically supports high data transmission rates (1 to 2 Mbps). The major
difference is that fast packet multiplexers can determine which transmissions are more important, such as
voice transmissions
- This multiplexing allows both the data and voice to be sent with less capacity on the multiplexed circuit. The
remaining capacity can be used for more data or voice transmissions.
Fast packet multiplexer
109
To achieve greater packet transmission speed, fast packet multiplexers remove _______ _______ from data
transmissions and gaps from digitized voice transmissions
repetitive characters
110
Advantages of using multiplexers to increase line utilization:
- does not affect the programs that send and receive data and
control signals on the low speed lines.
- high reliability and relatively low cost
- can handle continuous streams of data on some of the lines, as in remote batch operation,
without interruption of the stream or interference with other users.
- introduce no significant increase in response time.
111
Features of the multiplexers
1. alternate routing
2. terminal-to-host mapping
3. network management capability
4. integrated CSU/DSU
112
- similar to the multiplexer except that is usually a single-end device. At the terminal end, devices
connect to the concentrator that connects to the facility, and at the host end, the facility is routed directly into the
front-end processor
- Multiplexes several low speed communication circuits onto a single high speed trunk.
- differ from statistical multiplexers
- a device that acts as an efficient forwarder of data transmission signals. A
remote access hub is someteims refered to it.
-also called aggregator. A typical concentrator or
remote access hub is a device that handles incoming dial-up calls for an Internet (or other network) point-of
presence and performs other services.
- aggregates and forwards data packets within a system.
- may also administrate
various dial-up internet calls and function as a network router. In general, this term is used for
either of these essential tasks
- may also be part of troubleshooting efforts, where system administrators may check to see that
the concentrator is taking in and outputting signals correctly
Concentrator
113
The total capacity of the high speed outgoing circuit, in characters per second, is ____ to the total capacity of
the incoming low speed circuits
equal
114
Output capacity of a statistical multiplexer is ____ _____ the total capacity of the incoming circuits
less than
115
a node that broadcasts data to every computer or Ethernet-based device connected to it.
network hub
116
is any device that serves multiple other devices or users either with...
aggregator
117
is an access point from one place to the rest of the Internet.
point-of-presence (POP)
118
A concentrator or hub may be able to handle up to ___ dial-up modem calls, support a certain number of ISDN
(Integrated Services Digital Network),a set of CCITT/ITU standards for circuit-switched transmission,
connections and support leased line and frame relay traffic while also functioning as a router
100
119
Some IT professionals may use the term “_____________” to talk about a system that takes in buffered
packets and puts them into a single queue. The concentrator may take packets from FIFO buffers and put
them in a position for linear handling
network concentrator
120
IT professionals may talk about a network concentrator as a “_______” or more generally point out this
function within a network system that handles multiple streams or threads and combines them into a single
point of service.
forwarder
121
things to consider then evaluating multiplexers/concentrators
1. Line speed
2. Number and speed of ports supported
3. Redundancy
4. Protocol support
5. Security
6. Network Management Capability
122
The various functions of concentrator with buffering and processing capability will cover all aspects of
communications processing A device which can do the following functions can be called as
Communications processor
123
applications of communications processor
* Receipt of messages
* Transmission of messages
* Code conversion
* Speed conversion
* Message formatting
* Buffering
* Queue management
* Error checking and control
* Polling and addressing
* Message switching and routing
Comms 3 - Datacomm
flashcards
Decks in class (9)
# Cards
-
Lesson 1 - Introduction to datacomm55
-
Lesson 2 - Category of DataComm3
-
Lesson 3 - Configurations and Network Topology23
-
Lesson 4 - Standards Organizations for Data Communications14
-
Lesson 5 - Transmission Modes10
-
Lesson 6 - Two-Wire vs. Four Wire Circuits30
-
Lesson 7 - Types of Synchronization67
-
Lesson 8 - Network Components123
-
Lesson 9 - Network Components part 282
