1-2 DIGITAL AND ANALOG SYSTEMS
A digital system is a combination of devices designed to manipulate physical quantities or information that are represented in digital form; that is, they can take on only discrete values. These devices are most often electronic, but they can also be mechanical, magnetic, or pneumatic. Some of the more familiar digital systems include digital computers and calculators, digital audio and video equipment, and the telephone system-the world’s largest digital system.
An analog system contains devices that manipulate physical quantities that are represented in analog form. In an analog system, the quantities can vary over a continunous range of values. For example, the amplitude of the output signal to the speaker in a radio receiver can have any value between zero and its maximum limit. Other common analog systems are audio amplifiers, magnetic tape recording and playback eqipment, and the automobile odometer.