HUB
Hub refers to a networking component which acts as a convergence point of a network, allowing the transfer of data packets. In
its simplest form a hub works by duplicating the data packets received via one port and making it available to all parts, therefore
allowing data sharing between all devices connected to the hub. A passive hub simple acts as conduit for the data, allowing it to
go from one device (or segment) to another. So called intelligent hubs include additional features that allow an administrator to
monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable
hubs.
(Information sourced from www.webopedia.com)
K-BAND
K-band is a segment of radio spectrum that lies between 10.9GHz and 36.0GHz and spans the upper super high frequency and
lower extremely high frequency bands. It was developed as there were very few slots remaining for GEO satellites operating at
less than 17 gigahertz. Used especially for police radars, satellite communications and astronomical observation.
(Information sourced from www.britannica.com)
UTP
UTP is the most common form of twisted pair wiring available, because it is easier to work with than STP (Shielded Twisted
Pair). UTP is used in Ethernet 10 Base-T and 100 Base-T networks, as well as in home and office telephone wiring. The twist in
UTP helps to reduce crosstalk interference between wire pairs.
(Information sourced from www.tech-faq.com)
GSM
GSM (Global System for Mobile communication) is a digital mobile telephone system that is widely used in Europe and other
parts of the world. GSM uses a variation of Time Division Multiple Access (TDMA) and is the most widely used of the three
digital wireless telephone technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a
channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800 MHz frequency
band.http://www.tech-faq.com 26/10/08
Optical Fiber
Optical fiber (or "fiber optic") is the medium that transmits information as light pulses along a glass or plastic wire or fiber.
Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic
interference and the need to retransmit signals. Most telephone company long-distance lines are now of optical fiber.
Transmission on optical fiber wire requires repeaters at distance intervals. The glass fiber requires more protection within an
outer cable than copper.
http://searchtelecom.techtarget.com. 26/10/08
Infra Red
IR wireless is the use of wireless technology in devices or systems that convey data through infrared (IR) radiation. Infrared is
electromagnetic energy at a wavelength or wavelengths somewhat longer than those of red light. The shortest-wavelength IR
borders visible red in the electromagnetic radiation spectrum; the longest-wavelength IR borders radio waves.
http://searchmobilecomputing.techtarget.com 26/10/08
PSTN
(Public switched telephone network.) Basically the normal phone network, or land line.
PSTN is a ‘hard wired’ connection. It is the same thing as POTS (Plain Old Telephone System). It is simply the worldwide
telephone network. It carries analog data. In contrast, VoIP uses digital data.
http://www.in4ma.co.uk/faq/pstn.html http://searchnetworking.techtarget.com 26/10/08
NTSC
The National Television System Committee developed NTSC in 1953. Alternatives to NTSC were developed later, including
PAL and SECAM.
NTSC provides 482 lines of vertical resolution and 16 million colors. NTSC transmits 525 lines, but some lines are used for
sync, vertical retrace, and closed captioning.
NTSC delivers 29.97 frames per second. NTSC does this by delivering 59.94 interlaced half-frames per second.
Interlacing is a technique of alternating the transmission of even lines and odd lines to raise the effective resolution without
increasing bandwidth utilization.
NTSC has an aspect ratio of 4:3.
PAL is the predominant video system or standard mostly used overseas. In PAL, 25 frames are transmitted each second. Each
frame is made up of 625 individual scan lines
http://www.tech-faq.com http://www.ihffilm.com/videostandard.html 26/10/08
RGB
RGB stands for Red, Green and Blue. These three colours are the most prominent colours in the human colour spectrum. These
three colours are the primary colours. When red and green are joined they create yellow, Red and blue create magenta and Green
and blue create cyan. These are called the secondary colours and through the blending of these colours the computer screen can
make a colour display.
HMI
HMI stands for Human Machine Interface. A HMI usually consists of an Input device and an output device. This is were a
person will input information into a computer system usually through a keyboard and the resulting process will usually be
viewed on a computer screen. Input devices can be Keyboards, a Mouse and Scanners. Output devices can be a screen, Printer
or an output line
UHF
UHF stands for Ultra High Frequency. This is an electromagnetic wave which we can use to transmit information. The
frequency of this wave is between 300 MHz and 3 GHz. The main benefit of UHF is that the signal is at such a high frequency
the wave is quite short. This means that the signal is easier to pick up and there is no need for a large antenna. Televisions and
mobile phones are the most common use of UHF
Bluetooth
Bluetooth is a wireless technology, which connects devices and shares information over a short distance. It uses radio frequency
of 2.45ghz to transfer information. This can be utilised to replace the need for cables over short distances. The most noticeable
use of Bluetooth is in mobile phones and with the wireless headset. The use of Bluetooth as a short range information sharing is
growing.
ISDN
ISDN stands for Integrated Services Digital Network. This is the digital version of the old phone network. POTS (Plain Old
Telephone System). ISDN has a transfer rate of 128 kbps (128,000 bits per second). This is made up of two B channels of 64
kbps and a D channel for transmitting control information. The old system was only capable of attaining a transfer rate of 4800
bps.
ISDN brings more useful additions to the old system among these are High Speed fax, Video Conferencing and High Speed
Data Transfer.
The main advantage of an ISDN connection is the high speed, which it brings. Connecting to the internet can now be achieved
by a simple click instead of the old dial up process which could take as long as a minute.
Video conferencing with the old phone network needed many telephone connections, which needed to be checked extensively
before use and still did not guarantee a solid connection. This has been greatly improved with the use of ISDN lines.
Even with an ISDN line there can be a slow down through the amount of people who are using the system at the same time but
this is not nearly as bad as it would have been with the old system.
IP
Internet protocol everyone that uses the internet has an ip address it is a number that identifies every computer that uses the
world wide web the ip address is a very good invention that helps protect internet users
TCP /IP
Transmission control protocol/ internet protocol this was developed by the us defence department it ensures that when you send
information it gets to your intended destination and unaltered
POF
Polymer optical fibre is used for high speed data transport the polymer optical fibre offers great advantages when installing it.
It’s very flexible ductile and is much better than standard mode silica fibres and has made great improvements in past few years
MP3
The mp3 is a relatively new devise but has changed how the world listens to music it is replacing cd’s and tapes. The mp3 stores
digital music which is of much better quality it’s an amazing device that is very small in size but very big in memory. Mp3 files
can be downloaded or transferred with great ease the mp3 works in a very clever way its reduces the amount of memory a song
takes up as it take out parts of songs which the human ear can’t even hear so as you can see you have the same great quality
music but it takes up less memory so as you can see the mp3 is a remarkable invention of our generation that does it all when it
comes to music
GPRS and EDGE
General Packet Radio Service(GPRS) and Enhanced Data Rates for Global Evolution (EGDE) are 2 closely linked technologies
which allow relatively high speed data transfer over mobile telephone networks. Both work by allowing the transfer of packetbased data which allows multiple users to be online simultaneously. EDGE is a development of GPRS where the data transfer
efficiency is improved without the need for new network hardware.
Wakefield, T (2007) Introduction to mobile communications USA: Taylor and Francis, pp207-209.
3G
The third Generation (3G) of mobile phone networks allows users to send and receive large volumes of data over their mobile
phone handsets. Most 3G mobile phone handsets are still compatible with older 2G networks as 3G technology has not been
completely rolled out as it uses new technologies (UMTS, W-CDMA) which require new network hardware.
Wakefield, T (2007) Introduction to mobile communications USA: Taylor and Francis, pp209-210.
WDM
Wavelength-division multiplexing (WDM) is a process in which multiple signals can be sent simultaneously along an optical
fibre using different wavelengths of light to carry the different signals. WDM is analogous to FDM (Frequency-DM) in radio
signals. These techniques are a development of FM and PM in which only one signal is carried at a time. Filters at each end of
the cable separate the different modulated signals.
Haykin, S. (2001) Communication Systems. 4th ed., USA: Wiley and Sons, pp20-21
VGA/XGA/SVGA
Introduced by IBM in 1987 the Video Graphics Array display system is a technology which allows the display of information on
televisions, computer monitors, LCD screens etc. VGA cables carry data in analogue form where the data may be converted to a
digital signal or remain in analogue if it is to be displayed on a CRT screen. This conversion is typically carried out by a
graphics card or video adapter as required. VGA cable contains fifteen strands which are arranged in three rows of five each
with dedicated functions at the terminals. The different types of VGA have different capabilities as a result of the way they
handle the data especially the munber of bits they use to describe a colour in a pixel. VGA the most basic uses 8 bits per pixel
allowing it to deliver 256 different colours. XGA and SVGA use more bits per pixel (16 and 24 respectively) allowing them to
deliver 65,536 and 16.8 million colours. Recent developments in larger and wider screens have resulted in the need for the
development of new standards which are derived from the original VGA such as UXGA, QXGA, WXGA, WSXGA+ AND
WUXGA. These technologies cater to the increase in the number of pixels on modern screens. (Tyson and Carmack, no date)
Tyson J.and Carmack C.(June 2000) How computer monitors work [online] HowStuffWorks.com, [accessed 22 October 2008]
Available: http://computer.howstuffworks.com/monitor.htm
Cat 5e
Cat-5e or Category 5e, network cabling that consists of four twisted pairs of copper wire terminated by RJ45 connectors. Cat-5e
cabling supports frequencies up to 100 MHz and speeds up to 1000 Mbps. It can be used for ATM, token ring, 1000Base-T,
100Base-T, and 10Base-T networking. Cat5e cables are primarily used for networking, data transfer, and phone lines.
http://www.winncom.com/moreinfo/item/WRCCAT5-UVS-50/index.html
Bluetooth
Bluetooth wireless technology is a short-range communications technology intended to replace the cables connecting portable
and/or fixed devices while maintaining high levels of security. The key features of Bluetooth technology are robustness, low
power, and low cost. The Bluetooth specification defines a uniform structure for a wide range of devices to connect and
communicate with each other. http://www.bluetooth.com/Bluetooth/Technology/
UHF
UHF is an acronym for a band of radio frequencies often used to broadcast television signals. Mobile phones and satellite radio
also use UHF signals. The letters 'UHF' stand for: Ultra High Frequency. Any radio frequency between 300 MegaHertz (MHz)
and 3,000 MHz (or 3 GigaHertz) is considered to be in the UHF signal range. This range is less commonly known as the
decimeter range. Frequencies above the UHF band fall into the ‘SHF’( super high frequency ) and ‘EHF’ (extremely high
frequency) bands. http://www.tech-faq.com/uhf.shtml
FSK
FSK (Frequency Shift Keying) is also known as frequency shift modulation and frequency shift signaling. Frequency Shift
Keying is a data signal converted into a specific frequency or tone in order to transmit it over wire, cable, optical fiber or
wireless media to a destination point. FSK is still effective in many instances including the digital world where it is commonly
used in conjunction with computers and low speed modems. http://www.tech-faq.com/fsk.shtml
Cat 7
Category 7 cable (CAT7), is a cable standard for Ultra Fast Ethernet and other interconnect technologies that can be made to be
backwards compatible with traditional CAT5 and CAT6 Ethernet cable. CAT7 features even more stringent specifications for
crosstalk and system noise then CAT6. To achieve this, shielding has been added for individual wire pairs and the cable as a
whole.
The CAT7 cable standard has been created to allow 10-gigabit Ethernet over 100 m of copper cabling. The cable contains four
twisted copper wire pairs, just like the earlier standards. CAT7 can be terminated in RJ-45 compatible GG45 electrical
connectors which incorporate the RJ-45 standard, and a new type of connection to enable a smoother migration to the new
standard. When combined with GG-45 connectors, CAT7 cable is rated for transmission frequencies of up to 600 MHz. .
http://www.winncom.com/moreinfo/item/WRCCAT5-UVS-50/index.html
The advantages of CAT7 are, a higher bandwidth of up to 600 MHz as compared with Cat 5e (100 MHz) & Cat 6 (250MHz).
Individual pair shielding enable better NEXT isolation allowing different application to run in the same cable. Secure
transmission shielding keeps signal within cable.
The disadvantages of CAT7 are, individual pair and overall shielding increases the overall weight and size of cable. Hence needs
larger & stronger pathway and more stringent bend radius (100 mm or 4 inch). Individual pair and overall shielding means
higher labour cost and longer time to terminate cable. http://www.networkmagazineindia.com/200205/krone2.shtml
WAN (Wireless area network)
WAN is a wireless computer network that spans a relatively large geographical area.
Usually a wan consists of two or more local area networks. These computers are usually connected through telephones and other
public systems such as leased lines and satellites.
The largest WAN in existence is the internet.
LAN (Local Area Network)
A local area network supplies a group of computers that are in close proximity with each other with networking capabilities.
This is useful for sharing applications such as files, games, pictures, and printers. Most LAN are built with hardware such as
Ethernet cables, network adaptors and other inexpensive hardware. Wireless LAN and other expensive LAN hardware also exist.
MAN (Metropolitan area network)
A metropolitan area network is a network that operates over a larger area than a LAN but smaller than a WAN such as a big
town or city. These MAN are usually owned and operated by large corporations or a government body.
UPS (Uninterruptible power supply)
An uninterruptible power supply means that in the event of the failure of the primary source of energy, a secondary source is
available in a way that the load requiring the energy does not detect the break in the supply. Therefore nearly all of the standby
power applications for batteries could fall in to the category of uninterruptible power applications.
Ethernet
Ethernet was developed from an earlier application called Alohanet which was developed by Xerox. It was then further
developed by Xerox, Intel and DEC. Ethernet is the most commonly installed LAN technology and is also used in wireless
LANs . The most commonly installed Ethernet systems is the 10BASE-T which provides transmission speeds of up to 10Mbps.
A newer version of Ethernet called 100BASE-T (fast Ethernet)
Supports data transfer rates of 100 Mbps. The combination of the twisted pairs version of Ethernet as well as the fiber optics
versions is the most widespread LAN technology. Ethernet was named by one of its developers, Robert Metcalf, because of the
way that cabling could carry data anywhere throughout the network which is similar to the way
“aluminiferous ether” carried light throughout the universe. Network bridge devices are used to extend Ethernet to schools and
throughout whole office buildings.
Cross-Talk
Cross-talk is a disturbance, caused by electromagnetic interference along a circuit or a cable pair. A telecommunications signal
disrupts a signal in an adjacent circuit and can cause the signals to become confused and cross over each other.
HTTP
This stands for Hyper Text Transfer Protocol. It is used with web addresses because every different kind of communication on
the internet requires a different protocol. Hyper text transfer protocol is a defined set of steps that a user must follow in order to
obtain data from a web server. This process is followed for every single piece of data downloaded from a web server and this is
why the prefix “http//” is included in every url on web pages even including the links.
Bluetooth
Bluetooth technology is a short-range wireless radio technology that allows electronic devices to connect to one another.
Generally, Bluetooth has a range of up to 30 ft. or greater, depending on the Bluetooth Core Version. Newer devices, using
newer versions of Bluetooth, have ranges over 100 ft. Bluetooth wireless technology makes connections just like cables connect
a computer to a keyboard, mouse, or printer, or how a wire connects an MP3 player to headphones. Bluetooth technology makes
these same connections, except it does it without the cables and wires. With Bluetooth there is no more worrying about which
cable goes where, while getting tangled in the mess.
Bluetooth technology is actually derived from a combination of wireless technologies.
These were first developed by Ericsson and then formalized by a group of electronics manufacturers (Ericsson, IBM, Intel,
Nokia, and Toshiba) who joined together to form a private trade association known as the Bluetooth Special Interest Group
(SIG).
When they first introduced the Bluetooth specification to the public, they established a global standard, thus creating a universal
way for mobile computers, cell phones, and various other devices to wirelessly connect with one another.
UNIX
UNIX is an operating system that is now marketed by The Open Group. It was originally developed in the early 1970’s and is
still in use today. It was popular among programmers and universities in the beginning as it was written in a standard language.
It was also the first operating system to be mainly written in C and could be used on any computer that had a C compiler. Linux
is OS similar to UNIX and is available as freeware form some sites on the internet.
VoIP
Voice Over Internet Protocol is a system that allows voice to be transmitted over the internet. VoIP has become popular over the
past few years with providers such as Skype, it offers users with a good (broadband) connection to the internet to make calls for
free to other computers over the internet. Some companies allow customer to call landlines for cheaper than then standard rate
offered by the telephone company provider.
MPEG
MPEG stands for Moving Pictures Expert Group, they are the company that created the standard for compressing video and
music files into a smaller size. The company started in 1988 and released it first standard in 1993, MPEG-1. There are many
mpeg standards including MPEG-2,3,4. MPEG 4 is the latest standard relished in 1998 its is a high definition standard.
Server
Essentially a server is a computer that stores all the information in one place, and other computers connect into that computer via
a network. Technically all computers are servers. The advantages of using a server is that allows a users to save there files on to
the server form one computer and then access them form another computer on that network. The disadvantages is that if there is
any breach in security any one can look at you files on that network. Servers a usually used in offices and colleges. DIT has a
few servers in operation. All our emails are stored on a computer in anger sty that was up graded last year. Another good
example of a server is the internet. All the information is stored on millions of computers world wide that are all networked
together. This allows users to view information from all over the world as they can browse files stored on theses servers. Your
home computer connects to a server every time you go on the internet. Some routers have capabilities of being servers as they
have programs that allow users to play online games with out actually being on the internet because the router acts like the game
server you would be connecting to via the internet.
Coax
Strong and flexible, coaxial cable contains an insulated solid or stranded wire in the centre, surrounded by insulation. The
insulation is wrapped with an aluminium or copper sheath, which can be a wrapped foil or a braided wire fabric. The sheath
serves as the ground line and interference shield. All of this is wrapped in a plastic cover, which may have a fire-safe Teflon
coating. - sourced from www.pcmag.com encyclopedia
Token Ring
A local area network (LAN) access method developed by IBM. Conforming to the IEEE 802.5 standard, Token Ring uses a
token ring access method and connects up to 255 nodes in a star topology at 4, 16 or 100 Mbps. All stations connect to a central
wiring hub called the "Multistation Access Unit" (MAU) using twisted wire cable. Like Ethernet, Token Ring is a data link
protocol (MAC layer protocol) and functions at layers 1 and 2 of the OSI model. - sourced from www.pcmag.com encyclopedia
Scart
(Syndicat Français des Constructeurs d'Appareils Radio et Télévision connector) An audio visual connector used to hook up
VCRs and DVD players to TV sets and audio equipment. Developed by Peritel in France and also known as a "EURO
connector," the SCART cable uses 21-pin male plugs at both ends, while the devices use female sockets. - sourced from
www.pcmag.com encyclopedia
Ethernet
The standard local area network (LAN) access method. A reference to "LAN," "LAN connection" or "network card"
automatically implies Ethernet. Defined by the IEEE as the 802.3 standard, Ethernet is used to connect computers in a company
or home network as well as to connect a single computer to a cable modem or DSL modem for Internet access. - sourced from
www.pcmag.com encyclopedia
ATM
(Asynchronous Transfer Mode) A network technology for both local and wide area networks (LANs and MANs) that supports
real-time voice and video as well as data. The topology uses switches that establish a logical circuit from end to end, which
guarantees quality of service. However, unlike telephone switches that dedicate end-to-end circuits, unused bandwidth in ATM's
logical circuits can be appropriated when needed. For example, idle bandwidth in a videoconference circuit can be used to
transfer data. ATM is widely used as a backbone technology in carrier networks and large enterprises, but never became popular
as a local network (LAN) topology. ATM is highly scalable and supports transmission speeds of 1.5, 25, 100, 155, 622, 2488
and 9953 Mbps. ATM is also running as slow as 9.6 Kbps between ships at sea. An ATM switch can be added into the middle of
a switch fabric to enhance total capacity, and the new switch is automatically updated using ATM's PNNI routing protocol. sourced from www.pcmag.com encyclopedia
Bluetooth
Bluetooth is a wireless communication tool that allows information to be exchanged between Bluetooth compatible devices.
This system transmits via low power radio waves. It communicates at a frequency of between 2.402 GHz and 2.480 GHz. This
range of frequencies has been set aside for these Bluetooth devices by an international agreement called the ISM band. Bluetooth
avoids interfering with other devices by emitting a low signal, usually about 1 milli watt. This limits the range of Bluetooth to
about 10 meters. This system can connect up to eight devices simultaneously by using a technique called spread spectrum
frequency hopping. This technique causes the Bluetooth transmitters to change frequency 1,600 times every second, within its
designated radio frequency range. Spread spectrum frequency hopping makes it unlikely that two transmitters will be on the
same frequency at the same time, thus eliminating interference from external sources. When devices come in range with one
another, they set up an automatic personal area network. When this network is set up, the paired devices randomly change
frequencies together so they avoid other personal area networks in close proximity.
Ethernet
Ethernet was invented by Xerox Corporation in 1972 and was the first local area network (LAN). Ethernet is a standard bus
cable formed from 50 Ohm co-axial cable which all computers connect to. This Ethernet LAN can have up to 1024 attached
computers but in practice, it is far fewer. It is essentially a length of co-axial cable with a 50 Ohm resistor on each end. Ethernet
uses carrier sense multiple access protocol with collision detection (CSMA/CD) to prevent two computers trying to transmit at
the same time.
Local Area Network (LAN)
A local area network supplies networking capabilities to a group of computers in close proximity. LANs are useful in office
buildings and schools and for resources like file sharing and printers. A lot of LANs are built using simple Ethernet, network
adaptors and hubs. A LAN can also be connected to other LANs or the internet (WAN) which will increase its size. There is
special software available to control LANs and restrict access and to prevent viruses being contracted through the internet
(WAN).
ISDN
ISDN is integrated services digital network which is essentially a digital version of the simple telephone line system. This offers
a lot more than the telephone line system such as private virtual networks, high speed data fax and the most important, high
speed data communications. The ISDNs main advantage is its circuit setup speed. This allows for connection to the internet in a
matter of seconds, compared to almost a minute using a conventional telephone line system.
CSMA
CSMA is carrier sense multiple access. This is a protocol used by networks where a computer verifies that there is an absence of
traffic before transmitting or receiving data. It essentially listens for a carrier wave before trying to send information. When it
senses this encoded signal from another computer, it waits till the transmission has finished before sending back its own signal.
All computers on the network will receive the same signal but only the computer for which it was intended will answer and reply
to it, meaning it has multiple access points.
Fax
Fax is a method of telecommunication using a telephone network line. Still used regularly in businesses around the world, fax
allows people to send data such as text, photographs, diagrams etc by taking a photo cell copy of it and turning it one tone. As
there is a constant network available, data is transferred quickly and efficiently down the telephone line to a computer or another
fax machine.
Infrared
Is the transfer of data bi-directionally over short distances. Infrared works as a number of small waves are made and then sent
wirelessly to a receiver device. The transfer of data will only work if both devices are facing each other, as the waves cannot
travel through objects. The transfer rates are available in three sizes 115 Kbps (slow), 1.15 Mbps (medium) and 4 Mbps (fast).
These will also only work up to a range of about 16ft
FSK (Frequency shift-keying):
FSK (Frequency shift-keying) Is the transfer of data using digital signals of two binary states. These of which are two different
type frequencies waves. One of logic 0 and another of logic 1 which take a high low set of frequencies. The waves can travel
through cables or wirelessly and are read by the receiving computer in hi-low states as the receiving modem translates them.
Bluetooth
Is a device set up to replace the use of cables for transferring data. It carries qualities such as being energy and cost efficient over
other telecommunications and also offers healthy security. Having a max transfer rate of 3 Mbps it can operate over a distance of
10 meters to 100 meters depending on the device. Compared to other devices it allows data to be transferred through objects
such as walls and levels.
Bluetooth works as each device has a 48-bit address from the IEEE 802 standard. As the device changes the frequency
of its waves 1600 times a second, it stops all chance of interference from other connections etc. There are also three different
error correction schemes and encryption to protect from fraud or files being accessed.
A built in adapter powers the whole operation of sending and receiving data, as instructions are given by the user the
computer searches and then starts by connecting to a device to set up a line. This also allows more security as links can be
accepted or declined. From this the data is transferred
MIDI (Musical Instrument Digital Interface):
Is the transfer of data over channels in a sequence of bytes through controllers and synthesizers. There are two types of MIDI
bytes these are data bytes and command bytes. Each represent different binary numbers, hexadecimal and also decimal numbers.
This allows for many different values or signals t be sent at the same time but read on separate channels. It is used to send and
receive things such as volume, pitch bend and notes.
DSL
DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over
ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL AND RADSL. Assuming
your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to
receive data at rates up to 6.1 megabits (millions of bits) per second (of a theoretical 8.448 megabits per second), enabling
continuous transmission of motion video, audio, and even 3D effects. More typically, individual connections will provide from
1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL can carry both data and voice signals and the data
part of the line is continuously connected. Compaq, Intel, and Microsoft working with telephone companies have developed a
standard and easier-to-install formof ADSL called G.Lite that is accelerating deployment. DSL is expected to replace IDSN in
many areas and to compete with the cable modem in bringing multimedia and 3-D to homes and small businesses.
SMS
SMS (Short Message Service), commonly referred to as “text messaging”
is a service for sending short messages of up to 160 characters (224 characters if using a 5-bit mode) to mobile devices,
including cellular phones, smart phones and PDAs (Personal Digital Assistant).
POF
Plastic Optical Fibre (Cable), abbreviated POF, typically uses PMMA (acrylic), a general-purpose resin as he core material, and
fluorinated polymers for the clad material. In large-diameter fibers, 96% of cross section is the core that allows the transmission
of light.
CSMA-CD
CSMA-CD (Carrier Sense Multiple Access / Collision Detection) is the protocol used in Ethernet networks to ensure that only
one network node is transmitting on the network wire at any one time.
Bandwidth
Definition 1) In computer networks, bandwidth is often used as a synonym for data transfer rate-the amount of data that can be
carried from one point to another in a given time period (usually a second).
Definition 2) In electronic communication, bandwidth is the width of range (or band) of frequencies that an electronic signal
uses on a given transmission medium.
LANs (Local Area Networks)
LANs make up the physically smaller networked areas. They cover such areas as schools, libraries and businesses. LANs are
self contained using either Ethernet (cabled) or/and Wifi (wireless) connections to connect all systems and accessories to the
network. They then connect themselves, via a hub, to larger networks. The internal connections of these networks are important
as it negates the need to provide each pc, printer and accessory in the network with a separate leased line from a service provider
eg. Eircom. This type of connection also affords the network with a high data transfer rate within its network.
Ref: G.Fairhurst(at)eng.abdn.ac.uk - Date: 01/10/2001
http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm
MANs ( Metropolitan Area Networks)
These networks, as the name suggests, are city sized or at least big enough to serve a large group of buildings. They also act as a
stepping stone between LANs and the larger WAN networks. They are very commonly publically owned or owned by a service
provider who then sells the service on to its users.
Ref: G.Fairhurst(at)eng.abdn.ac.uk - Date: 01/10/2001
WANs (Wide Area Networks)
These networks are the physically largest of the networks incorporating global or semi-global networks. WANs are vast and
require the leasing of lines from communications companies to keep them connected. They can also come under the name NSPs
(Network Service Providers) when used as a means of connecting to the internet.
Ref: G.Fairhurst(at)eng.abdn.ac.uk - Date: 01/10/2001
POF (Plastic Optical Fibre)
Fibre optic cable is extremely thin, about the thickness of a hair and is normally made from glass or quartz. It sends information
in the form of light which is directed down its core by covering the cable with a material called cladding. This claddings inner
surface reflects the light by a technique called ‘total internal reflection’. POF’s are much larger with a core size of about 1mm
and although uses the same technology as its skinnier counterparts is only viable for transmitting data down short distances.
However it is cheap and being made from an acrylic/plastic material is more suited to transmitting through tighter radiuses than
glass fibre. It is utilised in car and home networks and because of its large diameter can also be seen transmitting by the naked
eye while in use.
http://www.vdvworks.com/LennieLw/fiber.html
MITSUBISHI RAYON CO., LTD. Optical Fiber Department: http://www.pofeska.com/pofeskae/tece/whatspofe/whatspofe.htm
NVP (Nominal Velocity Propagation)
This term is normally displayed as a percentage, which is arrived at by comparing the ratio between, the speeds of a signal
through a cable against the speed of light. It, as a constant for a particular type of cable, can then be used to calculate distances
between the source and terminations or inconsistencies in cables during fault finding.
http://members.aol.com/_ht_a/pattmann64/myhomepage/dictionary/Terms/2461HTML-2031.html
http://www.nationmaster.com/encyclopedia/Velocity-of-propagation
NOISE
This is irrelevant, unwanted signals that invade an electrical system. In electronics, noise can come from strong electrical or
magnetic signals in nearby lines, from poorly fitting electrical contacts and from power line spikes. Noise can block, distort,
change or interfere with the meaning of a message in electronic communication. It can alter the information content of a
valuable signal.
ATM
Asynchronous Transfer mode is network technology for both local and wide area networks (LANs and WANs). ATM efficiently
transmits video, audio and data. It organizes data into 53 byte cell units and transmits them using digital signal technology. ATM
is normally utilized by internet service providers on their private long-distance networks(WAN). However ATM hasn’t gained
in wide use as a LAN technology, in peoples homes and offices.
BLUETOOTH
Is a wireless technology which transmits data from one device to another at high speed and over short ranges (up to 100 meters),
creating wireless personal area networks (PAN). Bluetooth is common in many portable devices such as laptops, PDAs and
mobile phones. Some advantages of this wireless protocol are it eliminates wires and cable between both stationary and mobile
devices, and it facilitates both data and voice communication.
NOMINAL VELOCITY PROPAGATION
The Nominal Velocity of Propagation (NVP) is the speed of a transmitted signal sent along a cable relative to the speed of light.
NVP specifies the signal propagation delay in a physical medium in relation to the speed of light in a vacuum. Propagation
speeds over cables are usually 60% to 80% of the speed of light (c). Test equipment can calculate cable lengths by multiplying
the travel time by the signal speed in the cable.
ETHERNET
Ethernet is a network that was developed in the late 1970’s by Bob Metcalfe. It is the most widely installed local area network
(LAN). There are estimates that over 70% of the world’s networks use the ethernet protocol. This is a local area communication
technology, with networks operating typically in one building, connecting devices in close proximity to each other. Ethernet
devices are usually connected together by coaxial cable (or in more recent times with fiber optic cable), this provides a path
which electronic signals can be transmitted and received from one device to another.
To describe the basic Ethernet Bus, for example there 6 devices all connected with coaxial cable in a bus type system. If
machine 2 wants to send information to machine 5, machine 2 then transmits its data on the network. The signal gets sent down
the coaxial cable. The data sent contains destination address, senders address and information to be transmitted. The signal gets
sent down the cable to every device on the network but because it is addressed to number 5 all the other devices ignore the
information, whereas machine 5 receives the data. Collisions can occur when 2 devices try to transmit simultaneously both
signals collide and get destroyed, not a problem in small networks. When more and more machines are added to the network it
can slow the network down. A switch can be added to solve this problem.
Star topology
Star topology or star networks as they are also known as are one of the most common network setups. In this system, each of the
devices has its own cable, and therefore is easily isolated. Each device on the network is connected to a central hub. All data
goes through this central hub. A common cable that is used in the installation of star networks is the UTP (unshielded twisted
pair cable).The RJ45 is also used frequently. Advantages of a star network are that it’s easy to install, it can be expanded without
any great difficulty and faults can be easily detected. A disadvantage to it would be that if the central hub failed, then all devices
would go down with it.
FSK
FSK (Frequency shift keying) is a way of transmitting digital signals.FSK is a data signal converted into a specific frequency or
tone in order to transmit it over a wire, cable, optical fibre or wireless media to a destination point. It was discovered way back
in the early 1900’s.Despite its age, FSK is still in use today and it has adapted well to the digital domain. It continues to serve
those people who need to send data via computer.
STP
This is a wire made of soft annealed electrolytic copper. It has a pvc cable jacket.STP cable includes a metallic shielding over
each individual pair of copper wires. The four pairs of wires are then wrapped in an overall metallic foil. This protects the cable
from electrical noise within the cable(crosstalk ,pair to pair coupling)and any outside influences.STP cables are able to hold a
high quality signal even when passing near or parallel to mains power cables.STP can be difficult and expensive to install. The
metallic shielding has to be grounded at both ends. If it isn’t grounded sufficiently, the shield can act like an antenna and pick up
unwanted signals thus causing interference and poor data transfer.
LAN
LAN (local area network) is a computer network that covers a relatively small area. Most LAN’s just cover a single building or
group of buldings.One LAN network can be connected to other LANS over any distance via telephone lines and radio waves.A
system of LAN’s connected like this are called WAN’s (wide area networks).Local area networks usually connect personal
computers and workstations.Each individual computer in the LAN has its own CPU which it uses to execute programmes.It can
also access other data stored elsewhere on the LAN. This allows many computers to share expensive hardware like printers and
scanners.LAN users can also communicate with each other by sending email or engaging in chat sessions.LAN’s can transmit
data at very fast rates but the distances are limited. There is also a limit to the number of computers that can be used in a single
LAN.
Bluetooth
A Bluetooth connection is wireless and automatic. Bluetooth takes small area networking to the next level by removing the need
for user intervention and keeping power transmission low to save battery. It transmits data via low power radio waves; it uses a
frequency of 2.45 gigahertz. Bluetooth sends out very weak signals (about 1 mill watt) in order to avoid interfering with other
systems. It can connect up to eight devices at once. If all of these devices happened to be in the same 10metre radius, it would be
highly unlikely that any interference would occur between them. Bluetooth operates via a technique called spread-spectrum
frequency hopping, this makes it very uncommon for more than one device to be transmitting on the same frequency at the same
time. What this means is that a device will use around 79 individual frequencies within a designated range, which are chosen
randomly. The device will hop from one frequency in that range to another frequency on a regular basis. Like all wireless
networks Security can be a concern when it comes to Bluetooth. Devices can easily grab radio waves out of the air, so people
who send sensitive information over a wireless connection need to take precautions to ensure those signals aren’t intercepted.
Bluetooth has several security modes. Security methods include authorisation and identification procedures that limit the use of
Bluetooth services to the registered user. Also a user can switch his/her Bluetooth to “non discoverable” and avoid connecting
with other Bluetooth devices altogether.
PSK
Phase Shift Keying is a form of digital communication that changes the phase of a signal to relay information accurately. There
are two different forms of Phase Shift Keying, BPSK (Binary Phase Shift Keying) and MPSK (Multiple Phase Shift Keying).
BPSK as the name suggests has 2 opposing signal changes (0˚ and 180˚). The signal is divided into bits i.e. 1 or 0 and these
represent 0˚ 0r 180˚. This makes it easier to discuss the state of the wave. For example, if the wave does not experience any
change (the phase is not reversed) then the state of the signal remains the same (1 or 0). However if the phase of the wave gets
shifted the state of the signal will change from zero to one or one to zero. BPSK is often referred to as Biphase modulation.
MPSK opens more avenues for digital communication. There are many types of MPSK and two good examples of this are
QPSK (Quadrate Phase Shift Keying) and OPSK (Octal Phase Shift Keying). QPSK can divide the wave into 4 phases (0˚, 90˚,
180˚, -90˚) and effectively change the digital signal output. These shifts in phase are also represented by binary numbers for
example 0˚ is represented by 00, 90˚ by 01, 180˚ by 10 and -90˚ by 11. OPSK offers us eight phases (0˚, 45˚, 90˚, 135˚, 180˚, 45˚, -90˚, -135˚). The great advantage of MPSK is it offers the data at a quicker rate and this rate is measured in bps (bits per
second-the predecessor to the “baud rate”).
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213937,00.html
Bluetooth
Bluetooth is wireless connection that is used throughout the telecommunications industry. It operates at a formerly unoccupied
frequency (2.45GHz) and is available all around the world. In order for Bluetooth to be available to the user, a device must be
installed with a small but low-cost transceiver chip which allows the device to send and receive data. One disadvantage of
Bluetooth is it only works within a range of 10metres between the sender and the recipient (Class 2 most common), however
Class 2 can operate up to 100m away. A great advantage of Bluetooth is it works through walls and is cheap to operate.
http://wiredforwireless.blogspot.com/2008/09/what-is-bluetooth.html?gclid=CKbg6MeMpZYCFQocQgodZxEL6w
Frequency Modulation (FM)
Frequency Modulation is used everyday by people in mobile phones, cordless phones, television, and the most obvious one,
radio. This is done by attaching an audio signal (modulator) to a transmitting sine wave (AC signal/carrier). The carrier wave
becomes altered in accordance with the modulating wave (this enables people to distinguish the different sounds made by the
audio signal), however, it is important to be aware that the amplitude of the carrier wave never changes i.e. it is always constant.
The signal can be analog or digital the main difference being that analog is a gradual change while digital is almost
instantaneously changed.
http://wiredforwireless.blogspot.com/2008/09/what-is-bluetooth.html?gclid=CKbg6MeMpZYCFQocQgodZxEL6w
Amplitude Modulation (AM)
Amplitude Modulation is a method of transmitting signals by combining the carrier signal with the modulating/information
signal. The amplitude of the carrier signal remains constant, however, the amplitude of the resulting signal varies depending on
the instantaneous amplitude of the modulating signal. This is because the information in the modulating signal appears at
higher/lower frequencies to that of the carrier signal. These are known as sidebands and they use only 33% of the power
consumed in AM. The other 66% of the power is used in the carrier signal and is said to be useless because the carrier signal
carries no information. For this reason AM signals are inefficient.
http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci214073,00.html
10Base-2
10Base-2 is an Ethernet standard used in computer networking. The “10” in the name represents the standard's capability to
operate at 10Mbps. The “Base” refers to baseband as opposed to radio frequency and the “2” represents the maximum distance
a single cable can be installed (2 x 100m = 200m) although the actual maximum distance is 185m. The cable used is a thin
coaxial cable and it is terminated using BNC T-type connectors. 10Base-2 is often the cheapest network cabling option
available, hence it is also known as “Cheapernet”.
RGB
RGB stands for the colours red, green and blue. When the three colours are combined we get white. Each pixel that a computer
displays in RGB is given a red, green and blue value. RGB is the most common colour mode used when creating graphics, even
though most printers use CMYK or cyan, magenta, yellow and K, the key plate colour, black. The computer translates the
amount of intensity from each colour into 6 digits or 3 pairs. The first two for red, second for green and third for blue.
QAM
Quadrature Amplitude Modulation is a method of combining two AM signals into a single channel. Using this method allows
you to double bit rate. In a QAM signal there are two carriers with the same frequency but they differ in phase by 90°. One of
these is called the “I” signal and the other, the “Q” signal. QAM is used frequently in digital systems, especially in wireless
applications.
Ethernet
Ethernet is the most widely used Local Area Network (LAN) in the world today. It is usually cabled in twisted pair, but coaxial
cable can also be used. Ethernet is a system for connecting computers within a building using hardware running from machine
to machine. It was designed to work at 10Mbps but it has drastically advanced since 1973 when Bob Metcalfe designed and
tested the first Ethernet network.
DMX
Digital Multiplex (DMX) is a standard of lighting mainly used in theaters. DMX allows the operator to dim and control multiple
lights, smoke machines, colour scrollers and other compatible equipment, using just a single three-core cable from the control
gear. Using this system, you can avoid costly cabling of individual lighting circuits, and instead, dim and control up to 512
channels with a single cable. The system works using a “multiplexer” or “mux” usually incorporated into the lighting controller,
which takes the individual channel's data and encodes it into a format that can be sent down the DMX line with all the other
data. At the stage end (using the theater example) it enters a “demultiplexer” or “demux” where the data is split up again into
the individual channels and is then fed into individual dimming circuits. This is a very cost effective system that can be easily
modified without ever having to wire cables back to the control room. The information that is passed between the mux and the
demux is constantly being re-sent, this ensures that if a piece of equipment misses some information sent to it the first time, it
will be sent again in a matter of milliseconds. DMX512 as it's known is a hugely popular method of controlling stage lighting
worldwide and the standard is widely supported by equipment manufacturers.
Nominal Velocity Propagation (NVP)
Nominal Velocity Propagation expresses the speed at which an electrical signal propagates, or travels, the length of a cable in
relation to the speed of light through a medium. The NVP for a Cat 5 UTP cable is approximately 69% of the speed of light in a
vacuum, and this figure is vital to a cable tester when acquiring the measurement of a cable. The maths behind finding the length
of a cable is simply; the product of the NVP and the TDR (Time Domain Reflectometry) divided by two.
http://whatis.techtarget.com/definition/0,,sid9_gci1059969,00.html
AM
The concept of AM stereo is to send 2 independent audio signals within the 10 KHz bandwidth allocated by the FCC to each
commercial broadcast station. Additionally, the FCC requires compatibility with existing monaural receivers. Thus, if the 2
signals represent the left and right channels, a monaural receiver must recover the sum of these 2 signals.
REF: Analog and digital communication systems, second edition. Author Martin S Roden
FM
If you pick up any FM program guide, you will realize that adjacent stations are separated by 200KHz. The FCC has assigned
carrier frequencies of the types 101.1 MHz, 101.3 MHz, 101.5 MHz ….etc to the various transmitting stations. Thus, while the
bandwidth allocated to each station in AM was 10 KHz, it is an impressive 200 KHz for FM stations. This gives each broadcast
lots of room to work. The maximum frequency of the information signal is fixed at 15 KHz. Compare this with the 5 KHz of
AM to transmit this signal via a narrow band FM would require a bandwidth of 2 FM or 30 KHz. Since 200 KHz is available,
we see that broadcast FM can afford to be wideband.
REF: Analog and digital communication systems, second edition. Author Martin S Roden
SMS
Sms (short message service) has become a very popular service offered by GSM operators. It is particularly attractive to young
subscribers due to its low price. From the point of view of the service type it is classified as a teleservice. If the sms recipient is
outside the network range or its mobile station is turned off, the system will store the message for him/her and will deliver it as
soon as the mobile system reappears in the network. This is the so called store and forward mechanism. The sms can be
delivered in parallel to the ongoing speech transmission. An individual message is limited to 60 characters which are mapped
into 140 bytes thanks to applying the special alphabet.
REF: Mobile communications systems, published in English in 1999, Author Krzysztof Wesolowski
UTP
UTP (unshielded twisted pair) cable consists of two copper wires where each wire is separately encapsulated in PVC insulation.
Because a wire can act like an antenna, the wires are twisted two or more times at varying lengths to reduce crosstalk and
interference. By carefully controlling the number of twists per foot and the manner in which multiple pairs and twisted around
each other, manufacturers can improve the bandwidth. The minimum number of twists is two per foot, most new buildings are
prewired with UTP.
REF: Electronic communication systems, fifth edition 2004, Author Wayne Tomasi
FTP
FTP (foiled screened twisted pair) the cable is a multi core cable enclosed with a sheath of aluminum foil. It’s used where there
might be heavy noise adjacent to the cable. Disadvantage is that it requires care when earthing also electrical impedance must be
matched when connecting to an UTP system, this cable is typically used in factory settings.
REF: http://whatis.techtarget.com
IP: INTERNET PROTOCOL
According to my source, www.encyclopedia.com/IP this is a ‘network of networks’ that consist of millions of smaller domestic,
academic, business and government networks. Which together carry various information and services such as electronic mail,
online chat, file transfers and the interlinked web pages including other resources of the World Wide Web. The IP address is the
number that uniquely identifies each computer on the internet.
IP: is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte
destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The
organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department
to organization to region and then around the world.
TCP/IP: TRANMISSION CONTROL/INTERNET PROTOCOL
According to my source, www.yale.edu.pclt/COMM/TCTIP.HTM transmission control/internet protocol was
developed by a Department of Defence research project to connect a number of different networks designed by different vendors
into what is known today as the internet.
TCP/IP: is responsible for verifying the correct delivery of data from client to server. Data can be lost in the
intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and
completely received.
MPEG3: MOVING PICTURE EXPERT GROUP LAYER 3
The source I researched this information from was, www.tech-faq.com MPEG3 is an international standards organisation. Who
set the standards for compression and storing video, audio and animation in digital form. This was set up in 1988 and now has
three hundred members from several industries. MPEG can create high quality video files which other software like windows
also do. MPEG files can be decoded with the aid of software programmes. They can also attain high compression rates by only
storing the changes which occur between frames.
C.S.M.A: CARRIED SENSE MULTIPLE ACCESS COLLISION DETECTION
According to my source, www.webopedia.com/TERM/C/CSMA.HTML these are the rules determining how network devices
respond when two devices attempt to use a data channel together. Standard Ethernet networks use CSMA/CD to physically
monitor the traffic on the line at participating stations. If no transmission is taking place at the time, the particular station can
transmit. If two stations attempt to transmit simultaneously, this causes a collision, which is detected by all participating stations.
After a random time interval, the stations that collided attempt to transmit again. If another collision occurs, the time intervals
from which the random waiting time is selected are increased step by step. This is known as exponential back off.
Cable Modem
A cable modem is an instrument which allows the user to connect there computer to a nearby television. They have an advantage
over other telephone modems, because it has a quicker rate of download. Hence a normal telephone modem would only have a
speed of around 28.8 to 56kbps. Unlike a cable modem which has a rate of 1.5mbps (Anon, 2003).
Modem
The word modem is an abbreviation for modulator-demodulator. This is an electronic component which changes a computer’s
digital signals into specific frequencies as to allow them to travel over telephone or cable television lines.
Fax
The term fax is short for facsimile, and in some regions is known as telecopying. It is the transfer of scanned-in print material
which is transported by means of telephonic transmission. The desired location which the material is to be sent to is usually
defined by a phone number associated with a printer or other output device. The document to be faxed is scanned and treated as
a single fixed image, and in turn converts it to Bitmap.
MIDI
MIDI or musical instrument digital interface as it is also known can be seen as a major breakthrough in music technology. It first
came on the scene 1982, and had a major impact on the production of music. Its main function is to allow professional and
amateur musicians who may not have much technical knowledge to use powerful computer instruments and software. It also
originally contained new and time-saving tools for musicians.
Crosstalk
Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an
adjacent circuit. In a telephone circuit, crosstalk can result in your hearing part of a voice conversation from another circuit. The
phenomenon that causes crosstalk is called electromagnetic interference (EMI).
Source: www.searchnetworking.com
CSMA
Carrier Sense means that every Ethernet device listens to the Ethernet wire before it attempts to transmit. If the Ethernet device
senses that another device is transmitting, it will wait to transmit.
Multiple Access means that more than one device can be sensing (listening and waiting to transmit) at a time.
Source: www.knowledgerush.com
Binary
Binary is a numbering system comparable to our standard decimal system. The decimal system uses ten digits 0 through 9, and
is referred to as a base 10 system.
The binary system only has two digits 0 and 1 and is referred to as a base 2 system.
In effect binary is a system of 1s and 0s which relate to on and off electrical pulses. These 1s and 0s are commonly referred to as
a bit (binary digit).
Computers at their lowest levels perform all computations by manipulating flow of electricity to indicate “on” and “off” states.
These two states of electricity represent 1s and 0s to the computer and the binary digits or “bits” can be strung together to
represent numbers, characters, sound waves or anything else that can be described digitally.
Because of the way the binary system operates, every time you add a bit you double the capacity of the number. If we compare
each bit to a light switch, it can be set either on or off. With one light switch, two states are only possible so you can only have a
1 or a 0. Increasing to two switches gives us four possible outcomes: (1) both switches off, (2) switch A on, Switch B off, (3)
switch A off, switch B on or (4) both switches on.
Source: www.helpwithpcs.com/jargon/binary.htm, www.tech-faq.com
Noise
Noise is an unwanted signal energy that interferes with the required signal. Telecommunications signals carry both the intended
information and noise. Due to the fundamental laws of physics, noise cannot be reduced. The challenge when designing
telecommunications is to use a low signal level. The three types of noise found in telecommunications are environmental, man
made and internal noise.
ATM: Asynchronous Transfer Mode
Asynchronous Transfer Mode is a “virtual channel” in telecommunications. It’s designed to carry data communications such as
voice, video, text and wireless. ATM is made up of cells and they consist of an overhead field and then a payload field. The
overhead tells us what information has been inputted and the payload transfers this information. The cable we use for ATM’s is
fiber optic.
DSL: Digital Subscriber line
DSL is a high speed broadband internet connection using telephone lines. DSL is a much faster way for connecting to the
internet than using a normal phone line. It uses a higher frequency than voice and fax, so it doesn’t interfere with telephone
conversations or faxes which use the same phone line. The advantage of using DSL is that you still can use the internet through
the phone line and still make calls.
ISDN: Integrated Service Digital Network
Integrated service digital network is designed for a completely digital Telephone/ Telecommunications network. This design is
to change the analog system to digital because with the analog system there was noise in the network. Another problem is that
for longer distances more analog switches are included and with this there is more noise and poor quality. With digital there is
no noise. Digital communications are used for voice, data, image and video networks. It has a second benefit which provides a
single interface to use a fax machine, videophone, computer or microwave. When it was first designed they where going to use
fiber cable because it would be a lot faster and quicker than copper. But fiber cable would be a lot more expensive to install and
they decided to leave it with copper which is already in houses. The problem with copper is that it is a lot slower when using
video. The quality of fiber cable is much better than copper. The organisations responsible for ISDN have only set up a few
standards. Due to this, most companies are very slow in designing ISDN products because of very little standards to go on.
ISDN products are starting to be come more popular.
Half Duplex
Half duplex is that data is able to be transmitted in both directions on a single carrier but not at the same time. For example a
“walkie talkie” uses half duplex technology one walkie talkie sends the data on a radio wave; this radio can only receive data
and send data at the one time.
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212221,00.html
30 Sep 2004
BlueTooth
Bluetooth is one of the many ways in which electric devices connect to each other. Blue tooth is wireless and automatic and has
simplified our life in many ways. Blue tooth transmits data via low power radioim waves at 2.45 gigahertz this frequency has
been set aside by all governments. A verity of machines has used this technology to there benefit such as baby monitors, garage
doors and mobile phones head sets.
http://electronics.howstuffworks.com/bluetooth2.htm
© 1998-2008 HowStuffWorks, Inc.
TDR (Time Domain Reflectometry)
Time Domain Relectometry is today’s preferred method to analyse cable fault. It works by sending pulse down a cable and
examining the reflection of that pulse. By examining the reflection of the pulse faults in the cable can be isolated and found.
http://www.tscm.com/tdr.html
Binary
All computers use a form of communication called binary numbering system, which contains two unique numbers 0 and 1. The
computer and its C.P.U (central processing unit)work like tiny switches which can be either on or off. Computers call these bits
a bit is either off (0) or on (1). Consider a computer working at its peak at 50 volts so if we consider a closed electrical circuit
then reading would be at 1 and when it’s at 0 volts the same logic applies for a open electrical circuit. All operations that are
possible in decimal (subtraction, addition, multiplication and division) are equally possible in binary. In every day life we use
the decimal system because it seems more natural, for the computer we use the binary numbering system because of its electric
nature. As technology increased so did the rate in which we sent the bit rate 10 million in 1985,100 million in 1992, 1000
million in 1999 and now 100,000 million in 2008.A example of bit rate working to our advantage is in the way we watch
television with the increase in bit rate transaction the picture on our screen has improved High definition and blue rays disks are
examples of this.
http://www.webopedia.com/TERM/b/binary.html.Copyright 2008 Jupitermedia Corporation All Rights Reserved
Router
A device that forwards data packets along networks. A router is connected to at least 2 networks, commonly 2 LAN’s or WAN’s
or a LAN and its ISP’S network. Routers are located at gateways, the places where 2 or more networks connect. Routers use
headers and forwarding tables to determine the best path for forwarding the information, and they use protocols such as ICMP
to communicate with each other and configure the best route between any 2 hosts.
FSK(Frequency Shift Keying)
Frequency Shift Keying is a system, by where the high(1) and the low(0) binary signals are at different signals so as to allow
signals to be easily sent down a networking cable. Originally established in the mid-1900’s, it was at first very slow(45 bps) but
with the advancement of technology speeds have increased vastly to in excess of 1Mbps(1 Mega bit per second)
Cat 5 Cable
Cat (Category) 5 cable is a networking cable which consists of 4 twisted-pair cables
(white/orange,orange,white/green,green,white/blue,blue,white/brown,brown). Cat 5 can be terminated using an RJ45 plug top
connection or an IDC connection (Insulation Displacement Connector).Cat 5 can support frequencies of up to 100Mhz and can
also support speeds of up to 1,000Mbps.
ISDN
ISDN (Integrated Services Digital Network) is an international communications standard which is used for sending the likes of
voice and data aver digital or normal telephone lines. An ISDN system can support data transfer rates of up to 64,000 bits per
second (bps)
Bus Topology
Bus topology is a type of network where all nodes (computers) on the network are fed from a common networking cable. On this
type of system only one node may send information at any one time. The DAP (Data Access Protocol) decides which computer
can send on information at any one time. Each computer on the network is connected to the bus by a segment trunk. A bus
network is said to be a passive network because the computers are largely dependent on the Signal which is being received.
Advantages of a Bus Network
•
Very simple and easy to set up
•
Very little cable is used in the wiring so the network is cost effective
•
If one computer fails, the network as a whole will remain up and running
Disadvantages of a Bus Network
•
Fault Finding in the network is very difficult
•
Only one computer allowed to pass on information at a time
•
Not suitable for large networks as there is limitations on the amount of computers per network
Hub
A hub is a central unit for the distribution of information. A hub allows a device to communicate with other devices that are
connected to it. When a hub receives data it transmits the data to all the other ports on the hub. If two or more devices try to send
data then a collision occurs, if this happens then the devices wait randomly generated times and sends the data again. This is
called CSMA-CD, carrier sense multiple access with collision detect. The ports on the hub have both a receiver and a
transmitter. If the adapters didn't have to listen with their receivers for collisions they could send and receive data at the same
time, this is called full duplex. Because data can only flow one way at a time and a hub retransmits data from one device to all
other devices, the maximum bandwidth is 100 MHz and that bandwidth is shared by all of other devices connected to the hub. If
a device downloads a large piece of information from another device then the network becomes congested. This can drastically
slow the network connection down. This is a major downside to a hub.
Category 6a
Category 6a is also known as cat 6a. Cat 6a is a four pair augmented cable, this means the four twisted pairs of cable are
separated by a plastic divider. Cat 6a is capable of operating up to 500 MHz. It is used for the transfer of data and can provide up
to 10 G bit/s bandwidth up to a max of 100 meters
BlueTooth
Blue tooth technology allows electronic components to communicate wirelessly.
The technology creates a network or multiple (WPANs) wireless personal area
Networks. . This technology is now used widely in such products as computers mobile phones, wireless headphones and PDA’s
personal digital assistant. There are mainly 3 widely used classes of blue tooth. There can be some security issues
if Bluetooth is not correctly protected.
Classes Max Power (dBm)
Range
Class 1 100 mW (20dBm)
Class 2 2.5 mW ( 4 dBm)
Class 3 1mW (0 dBm)
~300 feet
~30 feet
~3 feet
PSTN
Public switched telephone network is the network of worlds circuit switched telephone network. Although originally a network
of fixed analog signals now it is nearly all digital and now includes mobiles as well as fixed line telephones. Some military and
large corporate companies would not be connected to the PSTN for security reasons. This was the earliest example of traffic
engineering and helped deliver the Q.O.S quality of service guarantees.
Ethernet
The most widespread of LAN technology Ethernet is a network of twisted pair cables connected to a hub/router probably
supported by a fibre back bone structure. It is widely used in the link up of offices and schools. With a common addressing
format point to point manageability and hubs to reduce installation costs. Used for sending data packs of information. An
Ethernet card is normally built in to your pc or lap top which enables us to receive information and signals.
Switches
A switch is used in networking to join multiple computers together. They operate just like network hubs however a switch is
generally more hi-tech and hence costs more than a hub. Switches operate very efficiently and conserve network bandwidth very
well. They are used in conjunction with Ethernet technology and can be linked together in order to increase the number of
computers on a network.
Routers
A router is used to connect a computer, or a series of computers, to a network. This can be achieved either through cabling or a
wireless system. The most commonly used router for home use is an IP router which connects the homes LAN (local access
network) to the areas WAN (wide area network).
Bus Topology
A bus topology connects many computers together onto the same network via a single cable which is ran throughout the
building. The cable, usually a coax type, is used to pass data between all nodes on the network. The advantages of this system
are that it allows a high rate of data transmission and is easily extended if required. The disadvantages include being difficult to
troubleshoot and having a limited length of cable and therefore limited number of computers available.
Bluetooth
Bluetooth technology was developed by mobile phone company Ericsson in 1994. It gets the name from a Scandinavian King
called Harald Blatand whose name was loosely translated into “Bluetooth”. His goal was to unite the world so this inspired
Ericsson to unite the mobile world whether it is via mobile phones, handheld computers or headsets. There are 3 different classes
of Bluetooth device. Class 3, which is the lowest power, has a range of only 10 metres. Class 2 has a range of 50 metres while
Class 1 has the best range of 100 metres. As it uses radio wave technology, Bluetooth is capable of passing through walls and
floors, making it extremely useful and it operates at the same speed as an average broadband connection. It is also a relatively
safe way to connect to other devices, offering pin code authorisation and 128-bit encryption. Bluetooth technology is constantly
and quickly evolving and will certainly be a big part in the future of telecommunications.
3G
This is the third generation of wireless technology. The main benefits of 3G are the improved multimedia aspects that it has to
offer. It’s roaming ability throughout Europe, U.S and Asia make 3G a highly useful piece of technology.
http://searchtelecom.techtarget.com/sDefinition/0,,sid103_gci214486,00.html
WDM
Wavelength-Division Multiplexing is a way of brining together numerous signals on laser beams at different infrared
wavelength for transmission along fiberoptics.
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214538,00.html
Duplex
This is the way in which information can passed in both directions at the same time. An example of duplex is a telephone.
Duplex is the progression of half-duplex were communication could not be passed at the same time, an example of this would be
walkie-talkies.
http://onlinedictionary.datasegment.com/word/duplex
GPRS
It has already been established that GPRS is a way of enabling phones to send and receive data at a much faster rate compared to
the standard 2G phones. While using GPRS your phone is always connected to WAP ( Wireless Application Protocol). As
already stated GPRS is extremely fast and operates at a speed of 171.2 Kilobits per second. The main benefit of GPRS to the
public is that GPRS you are able to send and receive pictures, videos and music.
GPRS has revolutionised telecommunication technology and is continuously finding ways to speed up the way information is
communicated.
http://www.meteor.ie/support/meteor_services/gprs_mss_wap_settings/
STP (shielded twisted pair)
Shielded twisted pair is a special kind of copper data cable which consists of several twisted pairs that have individual shields,
an outer shield and an insulator. The individual shield acts as a ground whilst the outer shield is used to provide protection
against electromagnetic interference. The pairs are twisted so as to reduce electromagnetic induction between pairs. This type of
cable is used for data communication in business premises such as office blocks and factories.
Category 5 cable (cat5)
Cat5 cable is a twisted pair Ethernet network cable and is one of the most commonly used in high speed network applications. It
consists of four pairs of copper wires which are either solid or stranded and can support speeds of up to 100 mbps. They have a
maximum run length of 100m. While the solid cable is better for fixed wiring and longer runs, the stranded is more flexible and
hence more suitable for movable cabling over short distances.
ScTP (screened twisted pair)
Screened twisted pair is very similar to STP but each twisted pair has not got an individual shield. Instead multiple insulated
pairs are enclosed in a common metallic outer shield that is encased in an outer thermoplastic insulation. As with STP, this cable
has excellent signal isolation properties provided by the outer shield which is a requirement for data communication
applications.
Integrated services digital network (ISDN)
ISDN is a telephone system network. It is the digital version of the plain old telephone system (POTS). ISDN involves the
digitization of the telephone network, which permits voice, data, text, graphics, music, video, and other source material to be
transmitted over existing telephone wires. It provides a single communications interface for connecting your phone, fax
machine, computer etc.
High definition television (HDTV)
High definition television is the highest form of digital television. It is said to provide up to five times more detail than standard
definition TV. It provides the best available picture quality due to its superior resolution, of which there are three different types,
720p, 1080i and 1080p.
The number stands for the amount of lines of resolution embedded within the signal, with the higher number giving a
more detailed picture. The “i” and “p” stand for “interlaced” and “progressive” which are types of scanning method. With
interlaced the 1080 lines are divided into two sets of 540 lines and painted on two different frames reducing the bandwidth while
in progressive you are getting 1080 lines at once which takes a greater bandwidth but also gives a better picture.
High definition can also be used to reduce travelling costs in businesses where company’s need to communicate between
different locations and HD allows them to hold high quality virtual meetings without having to leave the office.
As well as better picture quality, HD also provides better sound quality as it is a digital transmission with many HD programmes
broadcast in Dolby Digital 5.1 surround sound.
Star Topology
Star topology is a term used to describe the way in which a network of computers is linked together. In star topology, all the
nodes, or computers, are connected by their own individual cable or signal to a central computer, sometimes called a hub or a
switch. In order to communicate with other computers on the network, all data that is to be sent or received will have to pass
through the central computer. A star topology network is easy to install and easy to expand and add to. One other advantage of
this method of topology is that if one computer becomes faulty, it will not result in the entire network becoming unusable. The
faulty computer, because of its individual location on the network, can be easily identified and disconnected from the rest in
order to repair it. The star topology can be beneficial to companies and businesses too, as the central computer can filter out any
unwanted or potentially damaging emails or viruses from entering the entire network. One of the main disadvantages of the star
method however, is that should the central computer fail, the entire network will collapse and become unusable. Also, because
of all data being sent through the central computer, it is possible to get a bottle neck effect if large amounts of data are being sent
at the same time.
BlueTooth
BlueTooth was initially conceived by Ericsson, before becoming more widely and commonly used by the large number of
companies which use the technology today. Blue Tooth is an alternative way to cable to connect electronic appliances together.
The technology works by transmitting information and data on a specific frequency from one blue tooth device to another. It
requires very little power to use Blue Tooth devices and is relatively cheap. Blue Tooth is commonly used today in mobile
phone technology and connecting external devices, such as printers or cameras, to computers.
Ethernet
Ethernet was first designed and developed by the Xerox company in 1973, when a researcher was working on a way of linking
his computer to a printer. Ethernet uses cabling, usually twisted pair wire like cat 5, to allow electronic devices to communicate
with each other. It is mostly used in LANs in single buildings. The most commonly installed Ethernet systems are called 10
Base-T and are capable of transmission speeds of up to 10 Kbps.
ISDN
ISDN stands for integrated services digital network. ISDN lines are digital lines and don’t rely on converting digital data from
your computer into an analogue signal before transmitting it. A basic ISDN line has two separate channels, enabling your phone
to be used while your computer is connected to the internet. Each channel provides upload and download speeds of 64 Kbps
simultaneously, compared with analogue lines which have approximately 50 Kbps upload, and 32 Kbps download speeds
respectively.
Cat 5
Cat 5 is short for category 5. It is a type of cable consisting of four twisted pairs of copper wire, usually orange and
orange/white, green and green/white, blue and blue/white and brown and brown/white. The cable itself can support frequencies
of up to 100 MHz and speeds of up to 1000 Mbps. It is commonly used in Local Area Networks (LAN), connecting computers
together but can be also used for telephone lines.
Infrared
Infrared data links were first made as a cheap way to remove wires between computers and printers and also allowing wireless
computer transfers. The technology for this system is based upon cheap and miniature infrared LED and photo-detectors which
provide wireless connectivity within a 30 degree angle,1-meter range and with bit rates from 115kBits/s to 4-16Mbits.The bit
rates are grouped into four classes serial,medium,fast and very fast infrared.(Desurvire,2004,pp340)
Bluetooth
The name Bluetooth comes from a Viking Harald Blatand (Bluetooth) who unified Scandinavia around 920A.D. and was know
for his love of blueberries which stained his teeth.Bluetooth technology offers us low cost ,Omni - directional and short-range
connectivity(10cm to 10m).Up to eight Bluetooth units can be interconnected,forming what is called a piconet.A larger network
with more than eight connections is called a scatternet.(Dersurvire,2004,pp341)
Wi-Fi
Wi-Fi (Wireless Fidelity) is a popular non-profit trademark, corresponds to the 802.11b standard. The communication range for
Wi-Fi is around 100m indoors and up to 300m outdoors or inside an empty warehouse or airport hall. The transmission range for
Wi-Fi can be improved by using more powerful directive antennas. Apart from the safety considerations for people in business
and privacy concerns, Wi-Fi has become very popular way to connect to the internet without any wires in a public area like
cyber-cafes, shopping malls etc.(Dersurvire,2004,pp337,338)
RGB
RGB are the three primary colors of light - red, green and blue. These colors can be described as the computers native colors for
capturing images and displaying them on screen. Since the human eyes are sensitive to theses colors, all colors are taken as a
combination of these three colors. The primary colors come from human biology. They come from the human reaction to light
when it hit’s the eyes. The human eye has photoreceptor cells which usually respond most to green (medium wavelength)
yellowish-green(long wavelength) and bluish-violet(short wavelength) light. The human brain can very easily distinguish a wide
range of different colors based upon the variations in the signals that you can from the three colors. One of the most popular uses
of the RGB colour system is in the use of LCD or plasma televisions or computer screens. Each pixel on the screen can have a
certain value of red , green or blue. Theses values then change depending on what the person is watching. Cameras and scanners
also work in the same way, they capture the colour with sensors which record the varying ranges of theses colours at each pixel
on the screen. When all theses colours are at there minimum values the screen will come across as black, but when all these
colours are at there maximum values the screen will come across as white.(http://www.tech-faq.com/rgb.shtml)
DWDM
It stands for Dense Wavelength Division Multiplexing. It is an optical technology used to enhance bandwidth over fibre optic
backbones. It works at different wavelengths on the same fibre as a result of combined transmitted signals. One fibre is turned
into a number of virtual fibres.
(http://www.webopedia.com/TERM/D/DWDM.html).
Wi-Fi
It stands for Wireless Fidelity. It is a wireless networking technology used throughout the world. Wi-Fi may be related to any
system that uses the 802.11 standard, which was produced by the Institute of Electrical and Electronics Engineers (IEEE).
Computers with such a Wi-Fi network card can connect wirelessly to a router which is joined to the web via a modem. Any user
can connect to the internet as long as the user is within 200 feet or so.
(http://www.wisegeek.com/what-is-wifi.htm).
Bluetooth
It is the name of a wireless technology standard for connecting devices. It uses frequencies from the radio to transmit
information over short distances. By installing a Bluetooth chip and receiver into products, this eliminates cables that would
usually carry the signal.
(http://www.wisegeek.com/what-is-bluetooth.htm).
Simplex
It stands for one direction. An example of this would be the journey of the keyboard to the CPU. The CPU never sends
characters to the keyboard but keyboard always sends characters to the CPU. In a lot of cases, computers always send
information to printers but printers usually never send information to the computer. Simplex only needs one lane.
(http://www.connectworld.net/cgi-bin/iec/05DTHFDUP.html).
UNIX
A multiuser, multitasking operating system that is widely used as the master control program in workstations and servers. Both
Unix and the C programming language, which Unix is written in, were developed by AT&T. Unix and C were freely distributed
to government and academic institutions, causing it to be ported to a wider variety of machine families than any other operating
system. As a result, Unix became synonymous with "open systems."
SERVER
A computer or device on a network that manages network resources. For example, a file server is a computer and storage device
dedicated to storing files. Any user on the network can store files on the server.
VOIP
Voice over Internet Protocol, a category of hardware and software that enables people to use the Internet as the transmission
medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions. One
advantage of VoIP is that the telephone calls over the Internet do not cost the user more than their existing internet costs, the
same way that the user doesn't pay for sending individual e-mails over the Internet.
CSMA-CD
How network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard
Ethernet networks use CSMA/CD to monitor the traffic on the line at participating stations. If no transmission is taking place at
the time, the particular station can transmit. If two stations attempt to transmit simultaneously, this causes a collision, which is
detected by all participating stations. After a random time interval, the stations that collided attempt to transmit again. If another
collision occurs, the time intervals from which the random waiting time is selected are increased step by step. This is known as
exponential back off.
Server
Every machine on the Internet has its own IP address. A server has a static IP address that does not change. Your pc has an IP
address that is assigned by the ISP(internet service provider) when you dial in. That IP address is unique for your session and
may be different the next time you dial in. In this way, an ISP only needs one IP address for each modem it supports, rather than
for every customer.
Almost the entire structure of the Internet is based upon a client-server model. High-level root servers and DNS servers, and
routers direct the traffic on the internet. There are millions of servers connected to the Internet, running continuously throughout
the world.
NVP
The Nominal Velocity of Propagation (NVP) of a cable refers to the speed at which signals can pass from along a given type of
cable. This NVP is expressed as a proportion of the speed of light in a vacumn.
Bradford, R (no date)Nominal velocity of propagation [online] [accessed 22 October 08] Available:
http://www.anheng.com.cn/articles/faq/nvp.htm.