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Digital vs. Analog Signals

Think about how you communicate with other people on a daily basis. Do you call on your cell phone, text, or email? Have you ever used a landline to make a phone call? Not all of those messages are sent or received in the same way. Some signals are analog (landline) and others are digital (cell phone). Although both digital and analog signals deliver messages, they have more differences than similarities.

Analog SignalsAnalog signals are made up of continuously streaming data. Look at the picture of the analog clock to the right. Why do you think that would be? Analog clocks provide continuous data (as shown by the constant movement of the second and minute hands) just like analog signals provide continuous data.

Analog signals also have significant variation. Take a light wave, for example. In the visible light spectrum, you can see a full range of colors. There’s not just blue and green, but a multitude of other colors that fall between those two. Analog signals vary in frequency just as the waves carrying the information continuously vary.

We live in an analog world where things have a range of quality such as sounds that are louder or quieter, temperatures that are hotter or colder, lengths that are longer or shorter. Each of these observations are on a “sliding scale.” Instruments with dials or linear scales are typically analog equipment such as speedometers, pressure gauges, volume controls, and thermometers:

digital: a signal generated by sampling a stream of continuous data at regular intervals

analog: a copy of the waveform created by a stream of continuous data such as sound, light, pressure, temperature, and position

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Digital SignalsDigital signals, on the other hand, are like a light switch. They have two distinct values that they can send, rather than an infinite set of values like in analog signals. A common digital signal is binary code, a language of just zeroes and ones that computers use to communicate. A “1” in binary turns on the signal, while a “0” turns off the signal. Like a light switch,

digital signals have two values.

Digital signals waves have only two amplitudes, while analog signals have

varying amplitudes.

Analog vs. Digital?Which type of signal is a more reliable way to encode and transmit information? The answer is digital. Can you think of why this is the case? If a message is disrupted, digitized signals are able to pick it up more easily at the exact point the message dropped. (The segmented nature of the digital signal allows this.) Analog signals, on the other hand, are continuous; if they are disrupted, they must be restarted at the very beginning of the message.

If you record sound on a tape recorder, you are putting a continuous analog signal onto the tape. Digital signals aren’t on a sliding scale; they’re either ON/high or OFF/low. Those positions are called “1” and “0.” There is no “in between.” Notice the amplitude (crest) is only in two positions (up or down).

This is why more modern technological devices tend to use digitized signals rather than analog ones. Analog signals degrade over distance and must be amplified or boosted. Analog signals can produce “noise” or hissing on sound tracks or specks in image. Digital signals remain clear, take up less room, and can be secured with encryption. Using digital fiber optics is cheaper than analog copper wire. One disadvantage in using digital signals is that rapid improvements in technology sometimes result in equipment becoming outdated very quickly.

Digital vs. Analog Signals

Small fiber optic cable that carries digital signals is cheaper and less

bulky than analog copper wire.

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Show what you have learned about digital and analog signals by completing the Venn diagram below. Sort the words and phrases from the word bank into the correct places. Afterwards, add any additional words or phrases that will help you differentiate the two signal types.

Digital Signals Analog Signals

Word Bank

Transmitted as pulse More reliable Less reliableUsed by landline telephones Used by computers All electromagnetic wavesConverted into binary code Continuous IntervalsCell phones Send and receive information On or off

Digital vs. Analog Signals