Revision cards for Physics

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P1F Fast Facts

- Analouge signals have a continuously variable value.

- Digital signals are either on (1) or off (0).

- Everyday uses of infrared radiation include remote controls.

- Infrared sensors detect body heat.

- The advantages of using digital signals are that it is easier to remove noise and you can use multiplexing.

- Multiplexing is when you send more than one signal on a carrier wave.

- The advantages of using optical fibres are multiplexing and lack of interference in the final signal. 

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Explain how the properties of digital signals mean

- You are able to transmit several signals at the same time (mulitplexing).

- Switching off analouge means extra space for new services.

- Noise is easier to remove or ignore with digital.

- High quality signal with digital.

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Explain how the signal from an infrared remote con

- Remote controls emit pulses of infrared radiation to control devices such as TVs.

- The pulses act as a digital code.

- The device will detect and decode the pattern of pulses coming from the remote and follow the coded instruction.

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Describe why it is easier to remove noise from dig

Noise also adds extra random information to digital signals. However, this noise is usually lower in amplitude than the amplitude of the ON states. As a result, the electronics in the amplifiers can ignore the noise and it does not get passed along. This means that the quality of the signal is maintained.

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