This document provides an introduction to telecommunication networks and computer networking. It defines telecommunication as the transmission of signals over a distance for communication purposes. There are three main types of networks: local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs). Communication systems allow information to be sent from point A to point B and vice versa, using transmission mediums like cables or wireless systems. Key components of communication systems include messages, senders, mediums, receivers, and protocols. The document also discusses analog and digital transmission, transmission modes like simplex, half-duplex and full-duplex, and common communication devices like modems and routers.