We will start our understanding of switch theory on a beginners level ! Have you ever wonder how computers communicate or how they process data? In our technological age is pretty interesting to see people use computers everyday to do many common task as searching the internet, receiving and sending emails, blogging and etc. But do we truly understand or even care to know how the computer is able to complete this task for you? Or you might have a better question as to what is a computer! If you were to ask a normal user the question “What is a computer?” 95 percent of the people you ask will answer by saying that a computer is a collaboration of many gadgets(devices) or they could say “ Is that thing you use to surf the internet.” Both of this definitions given by the normal user are not necessarily false for the reason as we all know we do use a computer to surf the internet and what we call a computer is also compose of many input and output devices!

In Today’s class we will deal with Digital and Analog Systems.

Your probably wondering what is a digital and Analog system. Let’s start off with Digital systems since we are in a digital age.

Digital system

Digital Systems is a combination of devices designed to manipulate logical information or physical quantities which can take only a limited number of values, usually just two values are used: the positive supply voltage (+Vs) which in binary is 1 and zero volts (0V) which is represented in binary as 0.

Examples of Digital devices are:

· Computers
· Calculators
· Compaq Disk
· Digital Camera
· Digital Watch


In digital systems we could use Ranges to represent what the binary 0 means and what the binary 1 means. For example let’s say that binary 0 is a representation of any range from 0 to 2 V and binary one is a representation of 4 to 6 Volts. This is a clear cut difference from analog systems because in digital systems exact voltage are not important. To better understand what I’m trying to say look at the A animation. You can also see how binary is represented in the digital signal timing diagram.

Timing Diagram Animation A