66 lines
2.1 KiB
Markdown
66 lines
2.1 KiB
Markdown
# 1. Physical Layer
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This layer is responsible for the actual physical transfer of data between devices via cables or other mediums using switches, routers, etc..
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This layer also converts the data into a bit-stream of 1's and 0's.
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The signal convention must be the same on both devices. (Meaning of a 0 and a 1)
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## In depth
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Information on computers is stored in a digital format. To transmit this information we have to convert the information to signals.
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Physical layer is responsible for this conversion. The Physical layer deals with the actual physical transmission of electrical signals.
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You could say the physical layer is a bridge between real life and software.
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## Waves
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Waves, like you would see on a lake, or in electrical cables are made when a physical quantity changes in the form of a moving ridge.
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Waves by them self store no real information.
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## Signal
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A signal is a wave (carrier) that holds information. (wave + data = signal)
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The carrier is a type of wave we add our information to. In most cases a sine wave is used as a carrier wave,
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![[encoder.png]]
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A encoder converts analog or digital information in signals that can be transmitted across different [[Comminucation Mediums]]
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The process of adding data to a carrier wave is called Modulation
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## Modulation
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Adding data to carrier waves is called modulation.
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This can be done in 3 different ways.
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### Amplitude
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![[modulation-amplitude.png]]
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Amplitude or the strength (height) of a wave changes over time.
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### Frequency
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![[modulation-frequency.png]]
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Frequency is the amount of waves that pass a fixed point in a given amount of time.
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### Phase
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![[modulation-phase.png]]
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Phase specifies the location or timing of a point within a wave cycle of a repetitive waveform.
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![[modulation-phase-2.png]]
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## Analog
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**Analog Signals** can have a infinite number of possible values in a range.
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For example: 0.0 <-> 1.0
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- 0.1436367436473......
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- 0.54454764654765......
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**Analog data** is continuous and have continuous values.
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Values in analog data are always changing.
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A good analogy for analog data is like a physical clock with
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## Digital
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