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- 1—Digital signals-a series of pulses consisting of just two states: ON (1) or OFF (0). There are no values in between. DAB radio is Digital Audio Broadcast radio - it is transmitted as digital signals. The diagram shows a typical oscilloscope trace of a digital signal.
- 2—Analogue signal- Music and speech vary continuously in frequency and amplitude. In the same way, analogue signals can vary in frequency, amplitude, or both. You may have heard of FM and AM radio - Frequency Modulated radio and Amplitude Modulated radio. The diagram shows a typical oscilloscope trace of an analogue signal.
- 3Noise in analogue signalsNoise adds 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, for example.
- 4noise in digital signalsNoise 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, which is one reason why television and radio broadcasters are gradually changing from analogue to digital transmissions.
- 5optical fibresAn optical fibre is a thin rod of high-quality glass. Very little light is absorbed by the glass. Light getting in at one end undergoes repeated total internal reflection, even when the fibre is bent, and emerges at the other end.
Information such as computer data and telephone calls can be converted into electrical signals
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- GCSE Science FlashCards sobre Sem título, criado por s.ghillean em 26-02-2014.
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