Information systems experiments summary

OUTCOME 1:1.7 Gather and process first-hand and secondary information on the basic pattern of the information transfer process in the following systems:

o land connected telephones

o mobile phoneso televisiono radioso CD players

In any communication there is;- A step involving coding- A step involving transmission- A step involving decodinge.g. Telephone- Coding (mouthpiece)- Transmission (wire – electricity)- Decoding (earpiece)

LAND CONNECTED TELEPHONES Vibrations from voice box sound energy/wave Microphone – coding device

- converts sound energy to electrical energy Earpiece (loudspeaker) or ear – decoding device

- converts electrical energy to sound energy Transmission channels – wires, optical fibres (electrical/light

energy)Energy used in telephone communication;

ElectricalLight (optic fibres)MechanicalSound

System Code Coding device

Transmission channel or medium

Decoding device

Telephone Sound waves

Mouthpiece Electrical wires

Earpiece

RADIO Coding – radio transmitter Transmission channels – radio wave, audio signal, modulated

signal Decoding – ear, demodulating circuit, aerialTransmitting aerial – converts electrical energy EM energyReceiving aerial – converts EM energy electrical energy*Refer to radio transmission diagram

System Code Coding Transmission Decoding

device channel or medium

device

Radio Audio signal

Radio transmitter

“Space” via aerial

Diode or demodulating circuit

TELEVISIONSystem Code Coding

deviceTransmission channel or medium

Decoding device

TV Electrons Electrical signal

Wires, radio waves or optic fibre

Cathode Ray Tube (CRT)

Diagram:

MOBILE PHONES When phone is on, it is constantly checking for incoming calls and

looking for the CELL SITE with strongest power.

Sound Electrical Radio waves Transmitted via microwaves Electrical energy Sound energy

System Code Coding device

Transmission channel or medium

Decoding device

Mobile phone

Sound energy (waves)

Mouthpiece or microphone

Tower via microwaves

Aerial or earpiece

CD PLAYER A physical pattern is recorded as data on a CD “a series of flats

and bumps exists on what appears to be a flat disc surface” Photodiode – light energy electrical energy Transmission channel – digital signals are converted from the

original signal, amplified and converted to sound by the speaker

System Code Coding device

Transmission channel or medium

Decoding device

CD player Digital (light)

Laser light Electric current & laser light reflection

Photodiode

*RADIO TRANSMISSION DIAGRAM

1.8 Gather and process information from secondary

Technological/scientific advances and their benefit to society:

SYLLABUS POINT: To outline features that the systems have in common and use avilable evidence to discuss the applications of these systems

Common features: Encoding Storage Transmission Decoding Energy transformations Electrical energy use

Applications of these systems: Transmission of voice/sounds Transmission of images Transmission of text Emergency services Entertainment Business and commerce

sources to develop a timeline of communication systems introduced to society and use the available evidence to analyse the impact these systems have had on society and predict possible future directions in communication technologies

Technological or scientific advance

Benefit to society

Invention of writing *Improved quality of communication*Allowed messages to be sent*Allowed info to be stored for later use*Allowed for development of writing materials e.g. papyrus, paper

Invention of electricity *Allowed for invention of telegraph increased speed of communication esp. long distances*Submarine telegraph cables were invented to link people from overseas

Invention of wireless communication

*Much cheaper than telegram*Quicker*Allowed for ship-to-ship communication

Development of mass communication

*With printing presses, leaflets, newspapers distributed widely info is spread quickly*In contemporary times, mass communication involves broadcasting on the radio & TV

Timeline of communication systems/technologies;1870s – Bell invents the electric telephone1890s – Portable typewriter is invented1890s – Marconi invents wireless telegraphy long distance radio communication1930s – Regular TV broadcasting beginsLate 1930s – Atanasoff invents first electronic digital computer1950s – Laser is invented1980s – First optical fibre system is created long distance1990s – Berners-Lee invents the World Wide Web (www)1990s – VCRs become popular

Impact of TWO chosen communication systems on society;Telephone (1876)

Simple and fast communication Long distance communication reduces travel time Confidential Quality of communication was improved Versatile e.g. used in homes, businesses, entertainment

Electrical computer (late 1930s) Easy communication Convenient to use Used in many industries e.g. technology, multimedia, office

helped to create JOBS Easy access and storage of information Improved efficiency and quantity of communication

OUTCOME 2

2.4 Perform a first-hand investigation to observe ways in which waves can be modulated to carry different types of information

Wave modulation (modification) allows different information to be transmitted.

A wave can be modulated in 2 ways;Amplitude modulation (AM) – height of the waves

Frequency modulation (FM) – number of waves which pass a point in 1 second

Radio transmitter – the coding deviceIn the AM radio transmitter: One electric circuit produces the audio signal- Sound waves are converted into electrical signals Another circuit creates a carrier signal (function of a carrier

wave; to carry info from one place to another as an EM wave) A third circuit creates a modulated signal – i.e. the two

previous signals are “added” together

The audio signal carries speech and music and has a low, varying frequency.The carrier signal is an electrical signal with a high, constant frequency.Carrier and modulated signal both have a high frequency.

OUTCOME 3

3.4 Plan, choose equipment or resources for, and perform a first-hand investigation to compare the quality of reception of AM and FM radio waves

Background information:AM radio waves Have relatively LOW frequency but LONG wavelengths

o Long wavelengths allows for AM waves to diffract (bend around objects) with little loss of energy

o Useful when broadcast radio waves are needed Travel in straight lines Reflect off a layer of the atmosphere called ionosphere: allows

for OUT-OF-SIGHT transmission useful in long distance communication

Useful to carry only voice transmissions (quality of sound broadcast is relatively poor)

Susceptible to interference e.g. storms can severely affect the quality

Advantage – AM circuitry is not overly complicated, cheap and readily available / Disadvantage – crowded with users

FM radio waves Have relatively LOW frequency SHORTER wavelengths than AM waves therefore they do not

diffract as well objects reduce signal strength Travel in straight lines but spread out from a point source Must be LINE-OF-SIGHT as they do NOT reflect off Carry more information than AM waves higher frequency

than AM waves Generally higher quality than AMEXPERIMENT COMPARING FM AND AMIndependent variable – type of signalDependent variable – sound qualityControlled variables – weather, conditions

Validity of the data collected;By testing FM and AM signals from a set number of radio stations ensures data collected if valid. The tests were conducted in the same conditions to ensure accuracy of the results.

Conclusion;The reception and quality of FM radio waves have an overall good quality. There was not much interference when compared to AM radio. The quality of AM radio is relatively poor as there is constant background noise or static.

OUTCOME 3 CONTINUED

Table: Comparing AM and FM Property AM FMCost to produce Very low HigherEfficiency Low HighNoise (static) Significant LowRange Good PoorEM spectrum frequency usage

Wide Very wide

Interference from other stations with similar frequency

Serious Little

Reflections from buildings, hills and other objects

Little problem A little problem in some locations

OUTCOME 4

4.3 Gather, process and analyse information from secondary sources to identify the satellites used for ‘live’ telecasts from other regions of the world to Australia and vice versa and to present reasons why communication satellites have different aerials and positional orbits

Satellites that are used for ‘live’ telecasts from other regions of the world to Australia; Optus – 3 satellites (known as C1, D1, D2) AsiaSat – 3 satellites Intelsat – 7 satellites (on Indian and Pacific Ocean regions) Inmarsat – 2 satellites (on Indian and Pacific Ocean regions)

Service providers – Austar, Optus, Telstra, MediaSat, Netspeed

Why communication satellites have different aerials and positional orbits; A satellite can only receive and transmit to a maximum of

about 40% of the Earth’s surface. Therefore, to cover all countries requiring satellite

communications services, many satellites are needed in different locations

The use of aerials in the satellites assist in the communication between the microwave fields of the transmission towers as they provide directions.

OUTCOME 4 CONTINUED

Different aerials allow satellites to cover different footprints (e.g. Australia and Japan can be covered separately by different aerials on the same satellite) and;

Send and receive different types of data (e.g. TV, meteorological data, telecommunications such as telephones)

OUTCOME 5

5.4 Gather, process, analyse and present information from secondary sources to identify energy transfers involved in coding and decoding information by digital technologies

Digitally encoded information can be transmitted as; Light Electrical impulses Microwaves Radio waves TV waves

EXAMPLE in a fax machine;Light Electrical energy (Light energy if optical fibre is use) (EM energy if microwaves are used – mobile fax)

Electrical energy

OUTCOME 66.4 Perform a first-hand investigation to demonstrate the transmission of light through an optical fibre

Aim: to demonstrate total internal reflectionEquipment: light ray box, wires, rectangular/triangular glass prism, mirror, power supply (transformer)Set up:

Triangular prism

Light/laser beamRay box

Transformer

In this experiment, we tested the glass-to-air interface. That is when light is travelling from INSIDE the GLASS TO THE AIR.

When a wave reaches a boundary, it can be TRANSMITTED and REFLECTED. Light reaching an air/glass boundary cannot undergo total internal reflection. Light reaching s glass/air boundary undergoes total internal reflection. This happens if the incident angle is GREATER THAN the critical angle. It will only happen when the light is passing from an optically dense medium (glass) to an optically

less dense medium (air). When total internal reflection occurs there is NO REFLECTION of light.

6.5 Process and analyse information to compare and contrast copper cables with fibre optic cables in relation to:

o Carrying capacityo Costo Rate of information

transfero Security

Carrying capacity – optical fibre has greater information carrying capacity than any other medium (including radio, wireless or copper wire)Cost – much greater amounts of information can be transferred at a much lower cost per GB of data to the service provider and consumer. Optical fibre is therefore much cheaper using this criterion.Rate – information transfer via fibre optic cables is significantly faster than copper cablesSecurity – signals in copper wires can be ‘tapped’ more readily than optical fibre signals; copper wires present a greater security risk than optical fibres.

REFRACTION CRITICAL ANGLE

Represented by the HORIZONTAL LINE

SUMMARYOptic fibre Copper cable

Carrying capacity Higher/large Lower/smallCost Lower but set up

costs are very $$$Higher but getting cheaper since new technology is being introduce

Rate of information transfer

High (10GB/s) Low (2MB/s)

Security High security as it’s harder to tap into and intercept optic

Low security as EM radiation is emitted from copper cables which can be detected/decoded