P1f: Data Transmissions

Infrared radiation is not only useful for cooking and heating. It is used in remote controls to make life easier, whether it is changing channels on the television, opening car doors or opening the garage door when we get home on a cold, wet evening. Infrared radiation is also used to carry information in signals that can be transmitted over long distances using optical  fibres. This item considers how we use infrared radiation.

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Name two everyday uses of infrared radiation.
Remote controls (TV, automatic doors, video and DVD players) and short distance links for computers and mobile phones.
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How do passive infrared sensors and thermal imaging cameras work?
Infrared sensors detect body heat.
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What is the difference between analogue and digital signals?
Analogue signals have a continuously variable value and digital signals are either on (1) or off (0)
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What can communication signals either be?
Analogue or Digital.
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What happens as signals travel long distances? What is this called?
They become weaker and may also pick up random extra signals. This is called noise.
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How is noise heard on radio programmes?
As crackles and hiss.
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What might noise cause?
An internet connection to drop or slow down, as the modem tries to compensate.
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Talk about the effect of noise adding extra random information to analogue signals.
Each time the signal is amplified, the noise is also amplified. Gradually, the signal becomes less and less like the original signal. Eventually, it may be impossible to make out the music in a radio broadcast against the background noise.
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Talk about the effect of noise adding extra random information to digital signals.
This noise is usually lower in amplitude than of ON states.So the electronics in amplifiers can ignore the noise&it doesn't get passed along.So the quality of signal is maintained, a reason why tv&radio broadcasters are gradually changing to digital.
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What can information such as computer data and telephone calls can be converted into?
Electrical signals.
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How can electrical signals be carried?
Through cables.
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How can be electrical signals be transmitted?(2)
As microwaves or radio waves.
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What can electrical signals be converted into? What does this mean they can be transmitted by?
Converted into pulses of infrared radiation, and transmitted optical fibres.
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Why are optical fibres preferable over ordinary cables?
Optical fibres can carry more information than an ordinary cable of the same thickness. The signals in optical fibres do not weaken as much over long distances as the signals in ordinary cables.
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Why can optical fibres carry more data?
Because of multiplexing.
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What is multiplexing?
Where several digital signals are interleaved or carried together without being mixed.
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What can carry more data analogue broadcasts or digital radio and TV broadcasts? Why?
Digital radio and TV broadcasts because they can be multiplexed.
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What does multiplexing mean can happen? Give two examples.
Allows a more efficient use of the available radio frequencies, for example to carry many more channels or to allow high-definition (HD) television and ‘red button’ options.
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Other cards in this set

Card 2

Front

How do passive infrared sensors and thermal imaging cameras work?

Back

Infrared sensors detect body heat.

Card 3

Front

What is the difference between analogue and digital signals?

Back

Preview of the front of card 3

Card 4

Front

What can communication signals either be?

Back

Preview of the front of card 4

Card 5

Front

What happens as signals travel long distances? What is this called?

Back

Preview of the front of card 5
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