4.12 Digital Waves Lesson

Telephone Basics

​Before the telephone, people could not speak to people at a distance.

​Today we are seeing and hearing each other on opposit sides of the world.

​Smoke signals were used to send simple messages over long distances.

They were not easy to read and wind could make it so they could not be read.

They were used by the Chinese and Native Americans.

​Telegraph

​Before the telephone people sent messages by pigeons or people.
Then the telegraph was invented and it used Morse code to send messages.

​Your phone has a microphone!

​A speaker!

​In the past telphones used wires in your house. Now a cell phone sends out a signal to towers.
The towers change your cell phones radio or microwave signal to laser light.
That is then sent through fiber optic to where ever you call.

Right now that is how we are talking.

​Fiber optic cable caries laser light.

The light is reflected inside the fiber.

Networks will send your phone call to where it is going.

​The network is sending digital signals now.

These are 1s and 0s. Binary code.

This will then be changed back into your voice and or video.

​Cellular - a type of phone system.

​honeycomb - something full of small spaces like a beehive.

​range - The distance able to be reached by radio signals.

wireless - using waves instead of wires.

​disconnect - to switch off.

signal - a pulse or beat of energy.

Switch - a tool for connecting.

​Codes and Pixels

​digital - sending signals as a pattern of numerals.

internet - a system of computer networks around the world.

pixels - tiny dots of light on a screen that form an picture.

​Codes and Digital to numbers and letters

​01010011 01000011 01001001 01000101 01001110 01000011 01000101


_____ _____ _____ _____ _____ _____ _____

​Codes

​What is the code for your name?

​Morse Code

​Morse code was used by ships and by telegraphs and is still taught in naval schools today.