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Course: Archived AP CSP content > Unit 1

Lesson 2: Archived Physical network connections
Computing
Archived AP CSP content
Archived AP CSP Internet content
Archived Physical network connections
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How can we physically connect two computers?

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To make the global Internet possible, we need a way for two computers to communicate with each other, and it needs to work quickly across very long distances.
The very first network connections re-used the copper cables of telephone lines, communicating binary data via pulses of electricity.
Illustration of an Internet connection between two computers. A wire goes between the two computers, and has little lightning bolts going through it. The wire is labeled with the binary data "100110110110".
Engineers soon discovered how to send data in fiber optic cables as pulses of light and how to send data wirelessly via radio waves.
Illustration of a fiber optic Internet connection between two computers. A wire goes between the two computers, and has zig zagging lines going through it. The wire is labeled with the binary data "100110110110".
Illustration of a wireless Internet connection between two computers. 7 radio waves are shown radiating from one computer to the next, and are labeled with the binary data "100110110110".
The Internet still uses all of these types of connections, because they each have their own benefits and drawbacks, like faster speed or higher cost.
In the next video from Code.org, engineer Tess Winlock explains how computers send binary data over physical connections. Then we'll dive deeper into the types of connections and their speed.

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  • blobby green style avatar for user LiuYecheng
    Posted 4 years ago. Direct link to LiuYecheng's post “Light can move in cable? ...”
    Light can move in cable?
    What is the principle
    (1 vote)
    Default Khan Academy avatar avatar for user
    • aqualine ultimate style avatar for user Martin
      Posted 4 years ago. Direct link to Martin's post “```` ____________________...”

      ___________________________________________
        /\    /\    /\    /\    /\    /\    /\   
       /  \  /  \  /  \  /  \  /  \  /  \  /  \   
      /    \/    \/    \/    \/    \/    \/    \     
      __________________________________________

      Think about the straight lines as the "walls of the cable" and the dashed line as the light (they should be much steeper, but this is more about the idea). You send a light beam into the cable and it bounces from wall to wall (reflects from point to point) until it reaches its target.
      This way you can send large amounts of information very fast.
      Theoretically you could use mirrors to do something similar, but mirrors would absorb too much of the light with each bounce so you wouldn't be able to transport the light very far (although one or two bounces can certainly be done).
      (7 votes)