How Analog and Digital Signals Work

This tutorial explains the functionality of analog signaling and digital signaling. Learn how analog and digital signals work and how they transmit information.

To transmit information, two types of signals are used; analog and digital. Both types of signals not only have different properties but also function differently. In the below section, we will understand both types of signals in detail.

Analog signaling

This is the classic method of signaling. In this method, signals move like waves. The sending device converts data into waves and loads those waves on the media. The receiving device picks up those waves from the media and converts them back into the data.

example of analog signaling

An analog signal has four essential properties; amplitude, frequency, wavelength, and phase. The following image shows an example of these properties.

properties of analog signals

Amplitude

Amplitude measures the signals’ strength. At any point, in the given time, the amplitude is the height of the wave.

In our example:-

  • At 0 seconds, the amplitude is 0 volts.
  • At 0.25 seconds, the amplitude is +5 volts.
  • At 0.5 seconds, the amplitude is 0 volts.
  • At 0.75 seconds, the amplitude is -5 volts.
  • At 1 second, the amplitude is 0 volts.

Frequency

Frequency measures the number of cycles in a given time. In a given time, a frequency is the number of times that a wave cycles from its starting point through its highest amplitude and its lowest amplitude and back to its starting point. To express the frequency, unit Hz (Hertz) is used.

Hz = number of cycles per second

In our example, in one second, the wave completes one cycle (starting point - highest amplitude -lowest amplitude - starting point) so the frequency is 1Hz.

Few more examples:-

5Hz = 5 cycles in a second
30Hz = 30 cycles in a second
1 KHz = 1,000 cycles per second
1 MHz = 1,000,000 cycles per second

Wavelength

Wavelength is the distance between corresponding points of a wave’s cycles. It is expressed in meters or feet. It is inversely proportional to the frequency.

Higher frequency = shorter wavelength
Lower frequency = longer wavelength

For example, if a wave is transmitted on the 1 MHz frequency, it creates a wavelength of 300 meters while if the same wave is transmitted on the 2 MHz frequency, it creates a wavelength of 150 meters.

Phase

A phase is the progress of a wave in relationship to a fixed point and time. A phase is measured in degrees. By using different phases, multiple waves of identical amplitudes and frequencies can be transmitted on the same media.

For example, to transmit two separate waves of the same amplitude, one wave can be started at its lowest amplitude at the same time the second wave can be started at its highest amplitude. Since both waves have a 180 degrees phase difference, they both can carry different signals.

analog signal phase

Digital signaling

This is the modern method of signaling. In this method, signals are transmitted in binary form as pulses. In binary form, information is stored by using two types of bit; on bit and off bit.

To transmit both types of bits, two types of pluses are used in digital signaling; a pulse of positive voltage and a pulse of zero voltage. Both pulses are represented as on bit (1) and off bit (0) respectively.

To transmit a binary bit, an individual pulse is used. In other words, every pulse in digital signals represents a signal binary bit.

The following image shows an example of digital signaling.

digital signals

Differences between analog signaling and digital signaling

Analog signaling uses infinite and continuous waves to transmit the information. These waves are represented as sine waves. As sine waves have infinite variations, analog signals are more prone to distortion and noise. Human voices and natural sounds are examples of analog signals.

Digital signaling uses pluses to transmit information. These pluses are represented as square waves. A pulse either carries a positive voltage or no voltage at all. Since there are no infinite variations, digital signals are less prone to distortion and noise. Data storage devices such as hard disks and optical drives are examples of digital signaling.

That’s all for this tutorial. In the next part of this article, we will understand how analog signals and digital signals are converted into each other. If you like this tutorial, please don’t forget to share it with friends.

ComputerNetworkingNotes Networking Tutorials How Analog and Digital Signals Work