Analog and Digital Signals
How information travels as signals in waves: analog signals vary continuously while digital signals encode information as patterns of on/off pulses, and digitised signals can be copied, stored and sent with far less loss and noise
What a learner can do afterwards
- Explain the difference between an analog signal (continuously varying) and a digital one (a coded pattern of discrete values)
- Give reasons why digital transmission is more reliable (e.g., a 1-or-0 pulse can be cleaned up and recopied, while noise permanently distorts an analog wave)
- Trace how a real message gets digitised and sent (e.g., a voice becomes numbers, travels as pulses, and is rebuilt as sound)
The lesson
Every phone call, photo, and song you send travels as a signal: information moving from one place to another. Signals come in two types. An analog signal changes smoothly, taking any value in between, like a wave rising and falling. A digital signal is different. It encodes information as a coded pattern of discrete values, usually just two: on and off.
Think back to how a wave moves smoothly up and down. An analog signal works the same way. Its value can be anything within a range, and it changes continuously, with no steps and no gaps. A sound wave in the air, before anything digitises it, is analog.
When you talk into a phone, your voice starts out as an analog sound wave. A microphone measures that wave thousands of times each second and turns each measurement into a number. Those numbers become a stream of digital pulses, sent down a wire or through the air. At the other end, the pulses turn back into numbers, then into a smooth analog wave that a speaker can play as sound.
Digital pulses are simple: on or off, 1 or 0. If noise blurs a pulse a little on its trip, a receiver can still tell it was meant to be a 1 or a 0, and pass on an exact, cleaned-up copy. An analog wave has no such reset. Once noise distorts its smooth shape, that distortion stays, and it gets worse with every copy.
Analog signals change smoothly and pick up noise forever; digital signals use fixed on/off patterns that can be cleaned up and copied exactly.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.