A message with no words
You flick a torch on and off in a pattern. A friend across the field reads it. You have sent a message with light.
A cable and a Wi-Fi link do the same thing. They send ones and zeros as a pattern. The only difference is what carries the pattern.
Key words
| Word | What it means |
|---|---|
| Signal | a pattern of electricity, light or radio waves that carries data |
| Copper cable | a cable with metal wires that carries electrical signals |
| Fibre-optic cable | a cable with thin glass strands that carries pulses of light |
| Wireless | a link that carries signals through the air as radio waves |
| Tampering | touching or changing a link or device without permission |
| Eavesdropping | secretly listening to data as it travels |
| Signal loss | a signal getting weaker as it travels |
| Attenuation | the technical word for signal loss over distance |
| Access point | a device that gives Wi-Fi to nearby devices |
| Encryption | scrambling data so only the right person can read it |
| Ethernet | the common standard for wired networks |
| Network | computers and devices joined together so they can share data |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can describe the three signal types, and explain how tampering and signal loss affect each one.
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Three kinds of signal
Electrical: a copper cable sends changes in voltage. A high voltage can mean 1 and a low voltage 0.
Light: a fibre-optic cable sends tiny flashes of light down a glass strand. A flash can mean 1 and no flash 0.
Wireless: an access point sends radio waves through the air. The waves change in a pattern that a device reads.
Comparing the three
| Signal | Carried by | Typical reach | Easy to tap? |
|---|---|---|---|
| Electrical | Copper twisted pair | Up to 100 metres for Ethernet | Fairly easy, with the right tool |
| Light | Glass fibre | Hundreds of metres to many kilometres | Hard, and a tap can be spotted |
| Wireless | Radio waves in the air | Tens of metres indoors | Easy to hear, so encryption is vital |
The cells students fill in are left blank in this preview.
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.