If you are new to the Information Technologies arena, and wanting to get in, you should read through the Theory section first before moving on to other sections. Each section introduces a number of basic concepts that are central to understanding the technology Tutorials elsewhere in this site.

This Theory section is generally non-technical, and should not be memorized. It is presented here for you, the reader to give you a broad set of concepts used to discuss the technologies in the tutorial sections. You only need to be familliar with the concepts below.

Number Systems

Number systems are used to indicate quantities and values and there is more than one number system. The Information Technology field uses four numbering systems frequently: binary, octal, decimal and hexadecimal. To understand these, you have to understand why we use numbers and how these number systems work. If you are going to be in the IT field, understanding these numbers is basic to any study of almost any topic. Computers think in binary and represent their data in hexadecimal and octal. We humans use decimal. Until you know how to convert from one to the other, and understand them all, a lot of things are going to be a LOT harder.

Network Models

There are two major ways of looking at how networks work from an operational standpoint. The first, and most widely used for training purposes is the OSI Model. The second is the model that describes the basic functions of the Internet, the TCP/IP model. The OSI Model and TCP/IP model are used in several network certification exams.

Communications Concepts


This is the basics of generating a signal of nearly any type. Signal are used to carry data, and understanding basic signalling techniques help provide an understanding of essential physical layer protocols.


Modulation is how we get data 'encoded' into a signal. Modulation is the process of altering a signal in specific ways so that the signal can indicate a change of state that matches the flow of zeroes and ones in the data stream.


Quantization is the process of converting analog information to digital information. Quantization is used for storing music in digital format, for transmitting data across networks and transmitting voice, video and audio across digital networks.


The process of transmitting information can be simple on/off signals, or more complex mixed radio frequencies. The goal may be the same but the process always differs according to the method of communication used.

Network Models

There are two theoretical models of networking, the TCP/IP Model and the OSI Model.

The TCP/IP Model directly reflects how the Internet and TCP/IP based networks work. As the smaller, less complex model it is easier to learn. However, engineers more frequently refer to the OSI Model.

The OSI Model is a model of how networks should work. It is theory only, and not a hard science. It is a model designed to make it easier to categorize different technologies and protocols so that their operation can be more easilly described and understood.

Both the TCP/IP Model and the OSI Model are part of the Cisco CCNA certification exam, so you have to know them both.

Basic Cabling


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