M E A N S C O M M U N I C AT I O N AT D I S TA N C E
TELE-COMMUNICATION
NOT A NEW IDEA
EARLY DEVELOPMENTS FOR PASSING MESSAGES
THE MODERN ERA
Telegraph started in Europe in 1830s• Electronic transmission of morse code• Under the Atlantic in Cables
Radio transmissions from early 20th Century• Usually one way though there were radio phones• Use radiowaves
Telephone patented 1876 Alexander Graham Bell (but others involved!)• Converts sound into electronic messages in mouth piece• Message converted back to sound at other end. Used electric
cables
THE PHONE
CHANGES TO THE PHONE
Changed to optical
fibre
Became mobile
Used satellites for long-distance
Now use microwave
signals boosted
by phone masts
BASIC PHYSICS
Energy• Use longer parts
of EM Spectrum
Understanding• Basic grasp of
wave behaviour
technology• Optical fibres• Microwave
transmissions• Digital signals
WAVES
Longitudinal: soundTransverse: em
spectrum
KEY TERMS
1.• When waves interact you get constructive or
destructive interference
2.• Waves bouncing off things is called reflection
3.• Waves passing through materials change speed
and therefore direction at boundaries. This is called refraction.
WAVE INTERFERENCE
REFLECTION
REFRACTION
TOTAL INTERNAL REFLECTION
OPTICAL FIBRE
WHY REPLACE COPPER
1.• Fibre bundles much finer
2. • Much lighter
3.• Carry much more information. Separate
messages can pass down same cable simultaneously.
SIGNALS
SATELLITE TRANSMISSION
ATTENUATION
• Over a distance the energy in a signal is dissipated as it spreads out so the signal at any one point gets weaker.• This is why we need phone, tv and radio masts to
boost the signals. • Imagine as you move away from a light source in
the night – its effect gets less. It is just the same with radiowaves and microwaves.
ELECTROMAGNETIC SPECTRUM
EM SPECTRUM TELECOMMUNICATION
1.• light – • optical fibres
2.• IR • remote controls
3• microwaves• Telephones, GPS
4• UHF• TV
5• Radio waves• Radio transmissions
A BIT OF PHYSICS
• V = λ x f• Where v = velocity• λ = wavelength• f = frequency
• In the case of em spectrum v is called c as in Einstein´s famous equation
• E = mc²• C = 3 x 108 m/s• Rearrange the equation to find the frequency of 15
cm microwaves.
THIS MEANS
• As wavelength gets longer frequency gets lower1.
• High frequency waves attenuate more quickly so need regular boosting2.
• This is why we need lots of phone masts
• But relatively few radio masts.3.
TYPES OF SIGNAL
PRACTICAL DIFFERENCE
Analogue Digital
BENEFITS AND DISADVANTAGES OF ANALOGUE
Benefit• Allows much greater
info. storage• Easier to reproduce• Easier to send and
transport
Disadvantage• Looses information
DOES IT MATTER?
ThenOur brain perceives the Information to be analogue
Why not?Our senses sample information Like a digital signal
Digital loses informationBut does it matter? No!
E.G. FILM
• A moving picture is made up of 24 still frames a second• Our eyes use this discrete information and our
brain perceives it as if we were looking at movement in normal life.
• Conversely digital allows us now to project many more frames per second giving much greater resolution e.g phantom cameras.
CHALLENGE: A POSTER
Timeline of the development of
telecommunicationsSocial benefits
Financial and business benefits
Must include benefits to poor
people
Environmental costs
Social costsMust include an
academic article on effects on society or
individual
Explain a key area of telecommunicational
technology
RUBRICMarks
Timeline
Social benefits
Social costs
Economic benefit
Environmentalcosts
Example of technology
Effort
1 A comment
2 A relevant statement or comment
3 Some elements of task acheived
4 Generally achieved with some omissions or faults.
5 Includes all elements with times to scale
Explains how it has changed our lives for the better with before and after examples supported by quotes
Explanation of harm to society clearly put and based on a referenced article
Clearly explains how people benefit comapred with before and must include example alleviating poverty
Identifies pollution issues at all stages of life cycle with examples of types of harm
One area of technology explained in detail with diagrams
Full effort recorded by teacher and confirmed by team leader.