NETWORK COMPONENTS 1 Flashcards
is any device capable of sending and/or receiving information over a communications channel,
providing communications interface functions
Terminal
Basic terminal components
Input Mechanism
Output Mechanism
Communications Interface
provides input capability in
most terminals
keyboard
Captures data from the user or
environment (e.g., keyboard, touchscreen,
scanner)
INPUT MECHANISM
Handles data transmission between the
terminal and other systems (e.g., USB, Wi0Fi, Bluetooth)
COMMUNICATION INTERFACE
Displays or delivers processed data to the
user (e.g., screen, printer, speaker)
OUTPUT MECHANISM
is a device which ends a
telecommunications link and is the point at which a signal enters or leaves a network.
Terminal
converts network-provided signals
(optical, electrical, or wireless) into component signals, including voice, audio, video, data, wireless, optical, and interactive services, and is considered a network device on the premises that
is connected to a communications service
provider and is powered at the premises
Terminal
three types of keys
Text keys
Control keys
Function keys
A to Z, the numbers 0-9 and special characters.
Text keys
for the communication control codes, such as START, STOP, DELETE, and END OF TRANSMISSION
Control keys
which 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). Some terminals have only function keys, each key represents an item,
depression of the key actually enters the preprogrammed price of the item, its
identification and perhaps additional information.
Function keys
convert the character(s)
indicated by the pressed key into a serial bit stream for transmission over a data
link. Each character is represented by a code, generally either ASCII or EBCDIC
keyboard equipped terminal
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
NUMERIC PAD
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.
LIGHT PEN
A special monitor that lets the user make choices by touching icons or graphical buttons on the screen with fingers and are used for interactive displays in museums and in automatic teller machines
TOUCH SCREEN
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
It is upside down mouse, which is common in laptop computers.
TRACK BALL
A piece of hardware for digitizing images and come in several versions, from
grayscale to color, and capable of scanning a variety of bit depths.
SCANNER
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
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 theproduct.
BAR CODE SCANNERS
converts the beam into electrical pulses
photo diode
With digital cameras and digital camcorders direct digital entry is available for graphics and full motion video.
DIRECT DIGITAL ENTRY
Many systems can recognize pretrained
words if spoken distinctly with pauses between words.
DIRECT VOICE ENTRY
Output device that uses striking action to make impressions on paper.
Impact printer
T Y P E S O F I M P A C T P R I N T E R
Character printer
Dot matrix printer
These printers print on character at a time e.g., Daisy wheel printer.
Character printer
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
Dot matrix printer
each line is printed twice. The second printing is offset slightly so that it hides the individual dots
NLQ (near letter quality) mode
uses seven or eight dots vertically and five to eight horizontally
to produce a letter. The higher quality style of dot matrix printer uses
24 dots (or pins) vertically
standard dot matrix printer
Output device that uses laser beams or streams of
ink, rather than striking action, to make images on paper.
Non-impact printer
TYPES OF NON-IMPACT PRINTER
-Thermal wax transfer/ Dye sublimation printers
-Ink Jet/ Bubble Jet printers
-Laser printer
They use heat to transfer
pigment from a plastic ribbon to the paper
Thermal wax transfer/ Dye sublimation printers
It is a non-impact printer that shoots fine
streams of ink onto paper
Ink Jet/ Bubble Jet printers
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. __________ are high speed, high quality devices
which produce very high-resolution text and graphics, making them suitable
for desk top publishing
Laser printer
uses liquid ink
Liquid Inkjet
uses solid ink sticks
Solid Inkjet
Output device that uses computer directed pens to create complex, high quality images
Plotter
Two types of Plotter
Flat bed plotter
Drum plotter
It moves a pen up and sown across a flat drawing s
Flat bed plotter
In this paper is fixed or supported on a drum and pen moves only from side to side
Drum plotter
produce different colors by using multiple pens
Multicolor plotters
Examples of Plotters
Pen plotters, electrostatic plotters, dot matrix impact plotters
Terminals that provide user with visual display of input and output.
Video display terminals
It consists of cathode ray tube and its power supplies.
CRT display
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
CRT display
sweep rapidly a cross the inside of the screen from the
upper left to the bottom right of the screen.
Electron beams
To stop the image from flickering, the beams sweep at a rate of between 43 and 87 times per second, depending on the phosphor persistence, and the scanning mode used is interlaced or non-interlaced. This is known as _______ and is measured in Hz.
refresh rate
A very narrow display that uses one of several technologies, such as
electroluminescence, LCD, or thin film transistors.
Flat panel display
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.
Liquid crystal display (LCD)
are also back-lit or side-lit to increase visibility and
reduce the possibility of eyestrain
LCD screens
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
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
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/panels
Enhanced terminal components
Input Mechanism
Output Mechanism
Communications Interface
Buffer Storage
is 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
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
gives a single character as output at a time
unbuffered terminal
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
Intelligent terminal
It is the fundamental requirement for intelligent terminals.
Buffering
insert/delete line, display page (blocking of data), and others
Special editing function keys
if the internal memory of a video terminal exceeds the size of the screen, data can be
moved off and on the screen a line at a time (scrolling) or a block at a time (paging)
Paging/scrolling
such as Move Up/Down/Left/Right/Home/End, facilitate data input and editing.
Cursor controls
-the capability of displaying a form to be filled in by an operator
Format control
entered directly from the keyboard and executed by the terminal
Custom software programs
It is normally a teleprinter and a video display terminal. It is cheaper than intelligent terminal.
Dumb terminal
are characterized by their printing capability. These are usually
dumb terminals.
Teleprinter terminals (Hardcopy terminals)
has the advantage of the
processing capability of the computer to provide additional capabilities
PC terminals
A standalone information station that allows users to browse and retrieve
information
Interactive terminals
Kiosk
: 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
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
Remote job entry terminals
It is also called as remote batch terminal (RBT)
Remote job entry terminals
are special purpose terminals devoted to a particular type of application
Transaction terminals
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
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
include automatic teller machines (ATMs), passbook reader/printers, magnetic ink
character recognition (MICR) equipment, and the like.
Banking terminals
where users can deposit or withdraw money, make
transfers between different bank accounts, and pay bills
Automated teller machines(ATMs)
MICR
magnetic ink character recognition
are designed to withstand severe conditions, such as vibration and heat.
They are usually configured as input devices
Factory data collection terminals
Factory data collection terminals
Facsimile (FAX) terminal
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)
Terminal device that does not share a controller with another terminal
Stand alone terminal
Terminal through which data can be entered by means of a typewriter like keyboard.
Keyboard terminal
Terminal specialized by hardware and/ or software to display graphics in
addition to text
Graphics terminal
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
They allow several remote terminals at one site on a common multipoint circuit to share a single modem at that site. Modem
sharing devices do not multiplex; they simply provide a means of sharing the serial interface of one modem among several terminals.
MODEM SHARING DEVICES
These devices are also called as control units or cluster controllers
MODEM SHARING DEVICES
It is the 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
is a type of polling method where the control unit (or polling device) sequentially queries
each device in a network or system, one by one, to check if it has any data to send. Each
device is asked in turn, and if a device has data, it can transmit. If a device has no data, the
control unit moves on to the next one in the sequence. This continues until all devices are
polled
ROLL CALL POLLING
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
They allow interconnection of terminals or microcomputers to host mainframe computers
in many types of configurations.
LINE ADAPTERS
enable terminal users to connect to more than one network and switch between them, without plugging or unplugging any connector cables.
LINE INTERFACE MODULES
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. A port sharing device may be used when users want to exceed this designed capacity
PORT SHARING DEVICE
are similar to port sharing devices except in the matter of location. Line
splitters 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
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
They are used to connect two DTEs directly. They also are called null
modems.
MODEM ELIMINATORS
TYPES OF TERMINALS TO BE USED IN A NETWORK
DUMB TERMINALS
SMART TERMINALS
INTELLIGENT TERMINALS
TERMINAL EMULATION
have no processing power; not addressable; cannot respond to polling
messages; no error detection; located near host computer
DUMB TERMINALS
nonprogrammable; addressable; data stored in buffer to transmit block
mode; limited processing capabilities
SMART TERMINALS
contains own processor; runs applications; PC is example; provides better
line utilization; communication software must run in the terminal
INTELLIGENT TERMINALS
can emulate any of the 3 terminal types
TERMINAL EMULATION
sometimes simply referred to as
“mux”
MULTIPLEXERS
is a device that selects between a number
of input signals
MULTIPLEXERS
is a device that combines multiple
signals or data streams into one single signal that can be sent over a shared channel. This helps make better use of the available bandwidth by allowing several pieces of data to be sent at the same time
MULTIPLEXERS
ADVANTAGES OF MULTIPLEXING
EFFICIENT USE OF BANDWIDTH
INCREASED DATA TRANSMISSION
SCALABILITY
FLEXIBILITY
DISADVANTAGES OF MULTIPLEXING
SYNCHRONIZATION ISSUES
LATENCY
SIGNAL DEGRADATION
RESOURCE MANAGEMENT
provide end-to-end error checking and
correction, and circuit sharing
Multiplexers
A device that combines data traffic from several low speed communication circuits onto a single high speed circuit
Multiplexers
They can be used on multipoint circuits, but individual channels usually must each be for start stop data
Frequency division multiplexers
