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.