Comparing Analog & Digital Devices

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

What is the difference between analog and digital signals? Learn some examples of analog and digital devices, and how we convert between the two types of signals.

Analog vs Digital Devices

They say we live in an increasingly digital world. But what exactly does 'digital' even mean? You probably know that electronics, like computers, smart phones, and televisions are digital. But what is it about them that makes them digital?

Digital and analog really refers to a way of transferring and storing information. The natural world is completely analog. Information in the natural world is transferred using waves. You see a friend on the other side of the food court because a light wave bounces off them and enters your eye. You hear your favorite song coming out of a nearby store because sound waves from the store make it into your ear and vibrate your eardrum. Your eardrum physically moves up and down in a wave pattern.

Digital signals are different. A digital signal is what the computer understands, and is made up of patterns of electricity. Electricity is a flow of charge (electrons to be exact) around the circuit. You can send a signal using electricity by varying how fast those electrons move. In a computer, electrical signals represent the only language that computers really understand - binary code containing a series of ones and zeros. That's what a digital signal is - pulses of electricity representing ones and zeros.

Example of a digital signal - ones and zeros
Example of a digital signal - ones and zeros

So far this all may seem kind of abstract, but you probably know of many examples of both digital and analog signals. Most modern ways of transferring and storing information are digital: USB cables and sticks, HDMI connections, SD cards, CDs, and DVDs. All of these contain information stored as a series of ones and zeros, which are transferred from place to place using electricity. But you don't have to go too far back in time to find examples of analog signals and storage: cassette tapes, records, television through an aerial antenna, basic telephones, and most musical instruments were all analog. For example, cassette tapes and records contain actual bumps that represent the soundwaves that are stored in them.

A cassette tape
A cassette tape

The benefits of analog include the charm of the imperfections of the medium (like the hiss and pops of old recordings), the fact that less conversions need to be done, the information is more complete and exact (nothing is rounded), and that a computer failure cannot cause you to lose an analog recording. Sometimes analog signals can be better quality when compared to cheap digital equipment. The benefits of digital signals are that they can be transferred at the speed of light, tend to pick up less noise (like hiss in sound recordings), are cheaper, allow you to access any part of recording almost instantly, allow copies to be made without losing or degrading the original, and less of the signal is lost when transmitted over a long distance.

Converting Between Analog and Digital

Although the days of analog devices are going away fast, converting between analog and digital signals will always be important. Why? Because we humans are analog. When you record yourself singing a song, or create a home movie, you're taking things that are analog - that are physical and real - and converting them into digital signals on your smart phone or video camera. So how exactly does that work?

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