Talking across distances
For most of history, messages travelled only as fast as a person, horse or ship. Electronic communication changed everything by sending information as electrical signals or electromagnetic waves, often at nearly the speed of light.
A short history
| Year | Invention | Who |
|---|---|---|
| 1837–1844 | Electric telegraph and Morse code | Samuel Morse and others |
| 1858 | First transatlantic telegraph cable | Linked Ireland and Newfoundland |
| 1876 | Telephone | Alexander Graham Bell (first long-distance call in Ontario, 1876) |
| 1901 | First transatlantic radio signal | Guglielmo Marconi, received at Signal Hill, St. John’s |
| 1906 | First radio broadcast of voice and music | Reginald Fessenden, born in Quebec |
| 1920s–1950s | Television | Several inventors |
| 1962 | Telstar, first active communications satellite to relay TV across the Atlantic | |
| 1969 | ARPANET, ancestor of the internet | |
| 1980s–1990s | Mobile phones and the World Wide Web | |
| 2010s–2020s | Smartphones, 4G and 5G networks |
Analog and digital
| Analog signal | Digital signal |
|---|---|
| Changes smoothly, like a wave | Jumps between set values, usually 0 and 1 |
| Like a dimmer switch | Like an on/off switch |
| Old radio, vinyl records, old phones | Computers, smartphones, streaming |
| Picks up noise that is hard to remove | Noise can be filtered out; copies are perfect |
Most communication today is digital. Sounds and images are converted into long strings of binary digits (bits). Eight bits make a byte.
How a message travels
Every communication system has the same basic parts:
- Source: the person or device sending the message.
- Encoder (transmitter): turns the message into a signal.
- Channel: the medium the signal travels through (wire, cable, air, glass fibre).
- Decoder (receiver): turns the signal back into a message.
- Destination: the person or device receiving it.
Noise is anything that interferes with the signal, like static.
Wired communication
| Medium | How it carries information | Notes |
|---|---|---|
| Copper wire | Electrical pulses | Old telephone lines |
| Coaxial cable | Electrical signals with shielding | Cable TV and internet |
| Fibre optic cable | Pulses of light | Very fast; long distances; not affected by electrical interference |
Fibre optic cables use total internal reflection: light bounces along inside a glass strand thinner than a hair. Undersea fibre cables carry most international internet traffic.
Wireless communication
Wireless systems use electromagnetic waves, mostly radio waves and microwaves.
| Technology | Waves used | Range |
|---|---|---|
| AM/FM radio | Radio waves | Kilometres to hundreds of km |
| Television broadcast | Radio waves | Tens of kilometres |
| Cell phones | Microwaves | A few km to each tower |
| Wi-Fi | Microwaves (2.4 and 5 GHz) | Tens of metres |
| Bluetooth | Microwaves (2.4 GHz) | About 10 m |
| Satellite | Microwaves | Global |
| GPS | Microwaves from satellites | Global |
Modulation
To send information by radio, a transmitter changes, or modulates, a steady carrier wave.
- AM (amplitude modulation) changes the wave’s height.
- FM (frequency modulation) changes how closely the waves are spaced. FM has less static.
Digital systems use more complex modulation to pack lots of data into each wave.
Bandwidth and speed
Bandwidth is how much data can be sent per second, measured in bits per second (bps).
| Connection | Typical speed |
|---|---|
| Dial-up modem (1990s) | 56 thousand bps |
| 4G mobile | Tens of millions of bps |
| Home fibre internet | Hundreds of millions to billions of bps |
Satellites
Communication satellites orbit Earth and relay signals between distant places. Geostationary satellites orbit about 35 800 km up and stay over one spot. Newer low-orbit satellite networks fly much closer, a few hundred kilometres up, and provide internet to remote areas, including northern Canadian communities. Canada’s Anik A1, launched in 1972, was the world’s first domestic communications satellite in geostationary orbit.
Impacts
Electronic communication lets us video-call relatives, learn online and get emergency alerts instantly. But it also raises issues like privacy, misinformation, cybersecurity and screen time.
Common mistakes
- Thinking Wi-Fi and the internet are the same. Wi-Fi connects your device to a router; the internet is the global network.
- Thinking digital signals are always faster. Their main advantage is accuracy and resistance to noise.
Try it yourself
- Send a message to a friend in Morse code using a flashlight.
- Make a cup-and-string telephone. What is the channel?
- Draw the five parts of a communication system for a text message.
Quick recap
- Electronic communication sends information as electrical signals or electromagnetic waves.
- Analog signals change smoothly; digital signals use 0s and 1s.
- Wires, cables and fibre optics carry signals; radio waves and microwaves carry wireless signals.
- Modulation encodes information on carrier waves.
- Bandwidth measures how much data can be sent per second.