The basis of electronics is the electronic signal, an electric current that represents information. There are two basic types of electrical signals: analog and digital.
In analog signals, some continuously variable aspect of the electrical current represents the information. In amplitude modulated (AM) radio transmissions, for example, the amplitude, or strength, of the electromagnetic radio wave is proportional to the amplitude of the signal—the volume of the sound that the radio wave carries. The greater the amplitude of the radio wave, the louder the sound that radiates from the radio speaker.
Study of Signal Wave Form And their Frequencies