Document Type : Research Paper

Author

• Hasan Shamsi

Abstract

In describing electronic and electro-optic distance measurers, the word signal and the subjects of modulation and anti-modulation are frequently encountered. In this article we want to explain the
concepts of these three terms to the readers of the journal.
Signal is the general name for any voltage or variable current whose variation indicates a change in another natural phenomenon; for example, when speaking at the front of a microphone, the changes in the intensity of sound are converted into changes in an electronic voltage at the two outlets of the microphone circuit, which is called sound signal.
In telecommunication and radio communications devices, through the act of modulation, news, messages, audio and video signals are conveyed from one location to another using radio waves.