Analog vs. Digital Signals (ADC vs. DAC)

We as a society have used electrical signals for hundreds of years within our devices to transmit and receive information such as sound and video. Over the years, our advances in technology and the use of electrical signals have allowed us to effectively communicate and simply live our daily lives. Many devices from radios to sound recordings to televisions use some kind of electrical signal to carry data, whether it be analog or digital signals.

This blog post will discuss the differences between analog and digital signals and how they are used today to send and receive information and data.

Analog Inception

The first-ever analog reordering was captured in the mid-18th century, the year 1857 to be exact. A Frenchman named Leon Scott de Martinville, who was fascinated by human speech and written language, developed a mechanism to record sound so he could study the intricacies behind the way we humans communicate in more detail. He developed a machine called the Phonograph. The device consisted of a cone-shaped speaking horn with a flexible moving stylus connected to his smaller end. The cone gathered sound and transferred the changing air pressure, which moved the stylus, which recorded the data on a moving piece of paper. The Phonograph was built upon by Thomas Edison later in the century, and from there, we get the first modern form of signals, analog signals.

The "phonograph", created by etching soot-covered paper by Parisian inventor Edouard-Leon Scott de Martinville. Photo by Boston Globe

Photo by FirstSounds.org

Digital Inception

In the late 19th century, out of some of the flaws with analog recording, there came a need to package analog signals differently. Hence the digitalization of analog signals became mainstream. Analog signals were difficult to replicate and store in a scalable way. In the 1960s and 70s, there became a craze to convert analog signals into more efficient signals. Digital signals consist of 0s and 1s and are commonly known as binary. Binary signals are easier to store and copy compared to analog, therefore digital signals became more mainstream from the 1970s and on.

Photo by Study.com

Digital and Analog Signals Compared

Digital and analog signals are very similar in many ways but also each have their own characteristics that differentiate them. Let’s discuss some of the similarities and differences in this section.

Photo by Tutorialspoint.

Analog Signals

Analog signals are found in most of nature and are a great representation of sound or movement in particular. They are commonly used in communication systems that transport voice, data, image, or video information. Analog is recorded as a continuous up and down waveform; the key phrase is “continuous.” An analog signal can chart data at any range between the upper and lower limits of the application. There is no limitation to what range of data is recorded in analog. There is an infinite amount of values that an analog signal encompasses. Because of the continuous nature and the breadth of data points within an analog signal, you can capture data in the form in which it was originally produced. This is especially true when it comes to recording and reproducing sound.

Photo by MSP.

Devices that Use Analog Signals

For reference, here are some devices that you might own or remember from the past that use an analog signal:

Old CRT TVs

Old CRT (Cathode Ray Tube) Televisions run on an analog signal. The analog signal is used to display information in visual form.

Photo by Andre Moura 

Landline Telephones

Landline telephones are used to send verbal communication over a long distance. They also transmit voice signals or data through analog signals only.

Audio Tapes

The audiotape, also known as a cassette tape, is used for voice recording and playing. Audiotape records and plays audio with analog signals.

Antennas

The antenna transmits the analog signal from one circuit to another over a long distance wirelessly through the radio frequency signals. Remember TVs with the bunny ear antennas on them?

Digital Signals

Digital signals have become the norm when talking about modern technology. The digitalization of signals has taken innovation to the next level. One of the biggest reasons digital signals have become widely used in today’s technology is the simplicity of the data. Digital signals widely used in communication systems that transfer data using point-to-point or point-to-multipoint transmission channels, such as copper wires, optical fibers, wireless communication media, storage media, or computer buses. Digital signals are represented in 0s and 1s, better known as binary code. This code is set and cannot go beyond the 0s and 1s and is therefore confined to a limited set of standards. The 0s are when the voltage on the line is pulled low, and the 1s are when the voltage on the line is pulled high. Think of it as turning on and off a flashlight. When the flashlight is turned on, a 1 is represented, and when it is turned off, a 0 is represented. These 1s and 0s make interfacing with modern devices possible.

Photo by TechnologyUK

Devices that Use Digital Signals

For reference, here are some devices that you might own or use that use a digital signal:

Microprocessors and Microcontrollers

Microprocessors and microcontrollers are programmed and communicate with digital signals.

Digital Clocks and Stop Watches

Digital clocks and stopwatches are examples of digital devices.

Photo by Erik Mclean

Computer Keyboards

A computer keyboard is a digital device. When the keys are pressed on the keyboard, it sends signals to the computer in binary or digital signals.

Photo by Fox.

LED TVs

LED TVs, computer monitors, and displays are examples of digital devices that operate using digital signals. The main function is to display information or data in visual form.

Photo by Rachel Claire.

Digital Signal Advantages

Although analog signals do an excellent job at recording and transmitting sound and video and are still used in certain devices to this day, there may be circumstances where using a digital signal may be more appropriate . The main reason that the digitalization of analog signals has become so popular is that analog signals are very easily distorted and are very susceptible to interference, especially over long distances.

Since digital signals are simply 1s and 0s, a definite or more structured data set can be sent and/or received. Because of this, digital signals are an excellent choice when the application requires sending signals over long distances. But how do you convert an analog signal into a digital signal? That’s a good question, and we will answer that now.

DACs and ADCs

Since analog and digital signals are inherently different in nature, a device is needed to convert them from one to another. These devices are called DACs (Digital to Analog Converter) and ADCs (Analog to Digital Converter). These devices do as their name implies; they convert digital signals to analog and vice versa.

Analog to Digital Converter – ADC

An analog to digital converter is a device that takes analog signals and converts them to digital signals. The ADC, through a complex algorithm, converts the natural waveforms of an analog signal into digital, binary bits. The signal is processed through a DSP microprocessor from the ADC, so the signal can be transmitted from the device. These bits can then be sent and received with little to no signal interference over long distances. Since the binary bits are definite and structured, the same bits created from the analog signal by the ADC are the same bits that will arrive at the desired location, which can then be converted back to an analog signal through a similar device called a DAC.

Photo by Adafruit.

Digital to Analog Converter – DAC

A digital to analog converter is a device that takes analog signals and converts the signal from digital bits of data or 1s and 0s and converts it back to the natural waveforms of an analog signal. The data is converted through a complex algorithm that replaces the structured digital bits with analog wave signals that can then be heard or played back through a speaker.

Photo by Headfonics.

ADC and DAC Applications

One of the most widespread examples of DACs and ADCs in action is voice calling with a cell phone. As discussed earlier in this post, audio signals are analog due to the signal's waveform. When someone talks into a phone's microphone, the phone has an onboard ADC that converts the analog signal to a digital one that can then be easily sent to the other phone on the call. Generally, the signal is sent from the phone to a telephone tower, from the tower to a satellite, from the satellite to another telephone tower then from the tower to the receiver’s phone as digital bits of data. The long-distance travel is why the signal needs to be digitalized before sending. Analog signals simply would not maintain enough integrity to be received when transmitted through so many stations along such a long stretch of space. Once the phone receives the data, it processes and converts the digital bits back into an analog signal that can then be amplified through the phone’s onboard speakers and heard by the person on the phone.

ADCs and DACs are in various other applications as well, but a phone is a prime example of how and why these two devices are so important.

Conclusion

Electrical signals including analog and digital signals are a part of our everyday lives and are so important in the advancement of future technologies. Both signals are used to send and receive data between devices, whether it be video, audio, or some sort of encoded data. While analog and digital signals are both still used today, digital signals have particularly been on the rise in newer technologies due to its simplicity and accuracy.