Chapter 4 - The World Was Once Analog Introduction Sound, Vibrations, And Analog Recording (phonograph record) - An analog device maintains an exact physical analog of information. For example, bumps on an early phonograph recording correspond to vibrations that we perceive as sound. Analog Electronic Devices - An electronic device is analog if the amount of electrical current it generates is proportional to its input. - cassette tape player Many Electronic Devices Are Analog - At one time, most electronic devices used analog techniques to store, amplify, or emit pictures or sounds - AM/FM radios, stereos, televisions

Chapter 4 - The World Was Once Analog The First Analog Communication - Early telephones used an analog scheme to send voice from one place to another; the amount of electrical current sent between two telephones was proportional to the volume of sound Analog Is Simple But Inaccurate - An analog device always distorts the input and adds noise. Sending An Analog Signal Across A Wire [signal loss - attenuation] Digital Music - A technology is digital if it uses numbers to record information instead of a physical analog like bumps on a record or magnetism on a tape The Digital Revolution [transistor -> ICs]

Chapter 4 - The World Was Once Analog Computers Are Digital [Inside a computer, all information is represented by numbers] Digital Recording Using Digital To Recreate Analog [A-to-D converter] Why Digital Music? Summary –Information, including audio and video, can be encoded in digital form –The chief advantage of using a digital representation arises because the information does not become distorted while being stored, copied, or communicated