The purpose of this book is to introduce the basic concepts involved in electrical communication and further expand the reader's knowledge to more modern form of digital communication so that he can easily understand the processes involved in modern day data communication. The book is written for the readers with basic understanding of electronics and mathematics for engineers. Care has been taken to illustrate the concepts by illustrative examples; however the use of mathematics has been kept to minimum so that the readers of different branches of Engineering like computer engineering, Information technology etc. find it easy to understand without going into too much of details that may not be required for them. The book provides in-depth understanding of the fundamental processes involved in moving the data from one place to another. Chapter one has been dedicated to basic fundamental concepts starting with the definition of the signals, discussing sine wave and analysis of the real life signals by breaking it to its spectral components using the Fourier analysis. Chapter two focuses on the mechanism of transmission of signals. The need and various forms of modulations are discussed in adequate details. Special treatment is given to Digital modulation techniques which play vital role in transporting data from one place to another place. Techniques to convert data into a form suitable for transmission that is signals have been discussed qualitatively and further various forms of the media, through which the signals would be required to travel during its journey from one place to another and its effect on the signals has been discussed in detail. Chapter three discusses need for standards, methods and protocols for data transmission. Switching techniques are also briefly discussed which are essential part of any kind of multi-hop transmission system. Chapter four addresses the solution to problems of the different speeds of transmission and reception by different systems and also discusses the solution to the problems imposed by the media which asserts its effect by introducing errors in the received data. Chapter five gives brief introduction to telephone systems including integrated services digital network. Need for multiplexing systems and few multiplexing systems in use currently are also discussed in adequate details. Finally chapter six discusses the data security aspects and the need of reduction of used bandwidth. Few techniques have been discussed to give little exposure and adequate understanding needed at undergraduate level. Care has been taken not to go into unnecessary details.