A telegraph can be defined as any device or system that allows or facilitates the transmission of information by coded signals over some distance. The word telegraph is derived from the Greek words 'tele' meaning 'distant' and 'graphein' meaning 'to write'. It came into existence at the end of the 18th century to describe an optical semaphore system developed in [...]
After reading this essay you will learn about:- 1. Introduction to Telephone 2. History of the Telephone 3. Components 4. Advances in Telephone Technology 5. Making a Telephone Call 6. Equipment of Telephone Switching 7. Transmission System 8. Services 9. Evolution of the Telephone Industry 10. Telephone Industry Today 11. Recent Developments. Contents: Essay on the Introduction to Telephone Essay [...]
After reading this article you will learn about: 1. Introduction to Maxwell's Theory on Transmission of Waves 2. Development of the Concepts of "Field" 3. The Contributions of Heinrich Hertz 4. Unified Theory of Electromagnetism 5. Maxwell's Equations 6. Electromagnetic Wave Propagation. Introduction to Maxwell's Theory on Transmission of Waves: We have, so far, discussed the development of devices that [...]
After reading this article you will learn about the use of mathematics for the improvement in the methods of communication. Technical Limitations of Communications: The rapid developments in Information Technology have primarily been possible because of the introduction of networking which made it possible for organisations to move away from the concept of a sterile "computer centre" (that gave the [...]
This article throws light upon the top five schemes of encoding data bytes. The schemes are: 1. Non-return to Zero (NRZ) 2. Non-return to Zero Invert on Ones (NRZI) 3. Bipolar-AMI 4. Manchester Code 5. Differential Manchester Code. Scheme # 1. Non-Return to Zero (NRZ): A common way—probably the most common way—to transmit digital signals is to use two different [...]
After reading this article you will learn about the use of statistics for the improvement in the methods of communication. Statistics: Inventors are usually practical people, their forte being their capability to convert theoretical concepts into practical forms. Faraday, although a self-taught man from a humble background, became a famous inventor, but it was left to James Clarke Maxwell to [...]
After reading this article you will learn about: 1. Rules of Data Transmission 2. Analog and Digital Data Transmission 3. Transmission Impairments 4. Modulation 5. Modems 6. Error Detection 7. Error Correction. Rules of Data Transmission: The design decisions that concern the rules for data transfer require that one specifies whether data will travel in only one direction or both [...]
At the present time, there are three methods of connectivity available in India. These are: a. Connectivity through wireless transmission: b. Connectivity through telephone landlines: Connectivity through telephones includes three recommended methods. These are: Connectivity through dial-up lines; connectivity through leased lines and connectivity using ISDN (Integrated Services Digital Network). c. Connectivity through VSAT: Connectivity' through VSAT has two recommended [...]
The following example is adapted from an example given by Hughes Escort. This example may help to explain TDM/TDMA (Time Division Multiplexing/Time Division Multiple Access )technology in a very simple way. It seems many of us are working backwards in this age of technology. It is amusing, but true to a large extent. Instead of explaining the new technologies in [...]
Wireless communications may require the use of different facilities at different times. These are: Radio transmission and Microwave transmission. We shall look at each of them separately. 1. Radio Transmission: Radio transmission is one of the ways that wireless transmission can take place; the other widely used method of wireless transmission usually is microwave transmission. All these methods of transmission [...]