Introduction

Communication was initially dependent on the transport: roads between cities, between province / state and inter-country / continent. Then communication can occur through long-distance telegraph (1844), telephone (1867), radio waves elektromagnetik (1889), commercial radio (1906), television broadcast (1931), and then through television, the world so much smaller because people can see and get information about going on in other parts of the world. In telecommunications, the information delivered through the signal. Signals have two types:

1. Digital: specifically refer to the information that was represented by two
state 0 or 1. Digital data are sent to the two conditions are represented
namely 0 and 1.
2. Analog: the signal is constant with variations in strength and quality.
For example, sound, light and temperature that can change and strength
quality. Analog data is sent in the form of a sustainable, signal
development in the form of electrical waves
Television, radio and telephone is a telecommunications technology that uses analog signals, while using the computer for digital signal transfer
information. However, when this signal is also used for digital voice, image and combination of both. On the other hand, the computer that originally used as a calculator and data processing, is used as a means of communication since the network computer.