ABSTRACT
Internet uses digital technology to carry many forms of information, including documents, photos, songs, audio clips, and videos. Such information has not always been stored and communicated in digital form. This chapter describes the predecessor of digital, analog, and explains how analog signals are converted to digital form. Devices like a phonograph are called analog devices because they record and play an analog of sound. Analog communication was an important part of early telephone systems. The first telephones had two basic parts: a microphone to convert sound waves into an analog electrical signal and an earpiece to convert an analog electrical signal into sound waves. Unlike the analog devices, a computer is indeed a digital device. Digital recording only works because computer circuits operate at much higher speeds than the vibrations a human ear can hear. When someone plays a digital recording, a computer reads the numbers and uses them to re-create an analog electrical signal that the numbers specify.
