Chronological Developments of Wireless Radio Systems before World War II

By Vinayak Laxman Patil

This comprehensive and authoritative volume traces the history of research leading to the development of the wireless radio systems. It discusses the methods adopted by a large number of inventors and the results they obtained to provide perspective on how historical methods and events can be a source of inspiration for future research. This book will be of interest to researchers and students in telecommunications engineering as well as to teachers of history of science and technology. 

• Language: English
• Publisher: Springer
• Release date: Feb 15, 2021
• ISBN: 9789813349056

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© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021

V. L. PatilChronological Developments of Wireless Radio Systems before World War IIhttps://doi.org/10.1007/978-981-33-4905-6_1

1. Ancient Wireless Communications

Vinayak Laxman Patil¹  

(1)

Research Centre of Maharashtra Institute of Technology (MIT), Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, Maharashtra, India

Vinayak Laxman Patil

Email: [e-mail]

Abstract

The present chapter describes the ancient forms of communications adopted by animals and humans to send distress signals to their associates making typical sounds or some short symbols for immediate help which was then evolved for longer distances. Long distance communication using symbols was evolved as Telegraphy and long distance communication using phonetic sounds was then evolved as Telephony. The combination of both was further evolved as Television or Tele-Videophony. Due to human eyesight limitations, it was a challenge about How to send this information to longer distances. With the inventions of various forms of electricity, these problems were also comfortably solved. The representative information is usually represented by the symbols or textual form or voice. Such information was converted into electric signals for transmission to the longer distances using either wired or wireless media, while at the receiving end, electric signals were decoded to get the original message back.

1.1 Introduction to Long Distance Communication

From the very olden days, animals and humans use to send distress signals to their distant associates for getting their help in the need of hour. The signals such as flags, typical phonetic voices, or actions were used, and hence the field of telecommunication can be divided into two parts, one part deals with the transmission of conceivable information may be textual messages, letters or alphabets, coded messages that can be interpreted at receiving end called telegraphy, while another type is long distance transmission of the voice itself, which is called as telephony. In today’s scenario both symbolic information and voice signal are converted to their electrical equivalent that can be suitably transmitted over wired or wireless media to longer distances. This could happen because of intelligence possessed by the humans beings, they started exploring novel ways to send voice and information signals to longer distances, and as a result, you can see the great evolution of sophisticated systems like the internet applied for both the type of applications.

It all started with symbolic language for conveying specific information that was of interest and concern to their daily livelihood. Each discretely symbol conveyed specific information and since telegraphy deals with information it was ahead of developments of Telephony. The signal information may consist of visual information, audio information or audio-visual information and even data information. The branch that deals with sending voice signals to longer distances is called Telephony, while the branch that deals with sending both audio and visual information together is called as video signal to the longer distances is called as Tele-Videophony and yet another branch that deals with sending numerical information or data signals to longer distances is Telegraphy, while Telecommunication is a general designation for all these types of long distance communications.

1.1.1 Wireless Telegraphic Communication Methods

Since telegraphy was set to represent human signals using discrete symbols and since discrete signals were easy for communication as compared to continuous representing voice signals and hence the spread of wireless Telegraphy communication was rapid. This chapter specifically deals with various aspects of wireless telegraphic systems. The word telegraphy is derived from Greek words like t $$\hat{e}$$ le means distance and gr $$\ddot{a}$$ phein means to write. Telegraphy paved a way for the evolution of other types of communications.

The basic principles used in conveying the information or messages, used devices based on visual patterns of information (optical), electrostatic and relays operating on electromagnetic principles as shown in Fig. 1.1.

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Fig. 1.1

The principles adopted for sensing of symbols in various types of telegraph instruments

The Fig. 1.1 a represents the symbols those can be visible from sufficently large distance and interpreted by a person at the far end. In Fig. 1.1b, when the capacitor is charged, two hanging balls also get charged and repel each other and move apart and if the capacitor is discharged, then the balls move closer. In Fig. 1.1c, if the switch is closed, current flows through the coil and contact is magnetically closed, while if the switch is opened, coil gets de-energised and contact is opened.

1.2 Origin and Very Early Forms of Communications

Smoke and light signals have been the oldest forms of visual signalling [1] for sending the distress signal for getting help from the communities staying at longer distances and dates back 588 BC as reported in the earliest reliable record of writings of Jeremiah by communicating intelligence to others by the signs of fire. Homer was the first person to make a mention of telegraphic art, and the Roman generals took the help of such methods for distant communications during wartime.

During BC 264, Polybius wrote Punic Wars where in he mentions that he was able to improve communication by use of Communicating ideas by letters which was used by Cleoxenus in his telegraph. During BC 1084, Troy city was besieged by Agamemnon, who signalled this event to his queen Clytæmnestra.

1.2.1 Aerial Telegraphy Using Semaphores

The visual telegraph system was used in Europe and Asia for conveying the letters in symbolic fashion or in the form of patterns that were communicated visually. These systems were then superseded by electric telegraph systems.

1.2.2 Claude Chappé’s Optical Telegraph

In 1794, Claude Chappé [2–4], French origin inventor, worked hard to successfully establish first aerial telegraph line using line of sight communication between Paris and Lille. It was, in fact, optical telegraph and semaphore or flag based alphabets that released information from one hilltop to other. It used two movable arms to represent various position of arms to represent visual information that codified various alphabets as shown in Fig. 1.2. However, such systems could not be used in foggy