Introduction

Modern communication systems are all around us — the phone in your pocket, the Wi-Fi at home, the glass fibres that carry the internet, and the satellites that relay television and long-distance calls. This final chapter of the Karnataka 2nd PUC Electronics course gathers these technologies together and examines how each of them moves information from one place to another.

We begin with the cellular mobile phone network, following how a call is set up, how it is handed from one cell to the next, and why the coverage area is broken into a honeycomb of hexagons. We then look at the Internet, Wi-Fi and Bluetooth — the wired and wireless links that connect computers and everyday devices — followed by optical fibre communication, in which a beam of light carries the signal, and satellite communication, where a repeater in orbit bridges two distant ground stations. The chapter closes with RADAR, which uses reflected radio waves to find the range and direction of a distant target.

Running through every topic is one core idea in many different forms: a transmitter, a channel and a receiver working together to carry a message reliably. Understanding the block diagrams and the key terms in this chapter is worth steady, dependable marks in the II PUC board exam, and it also explains a great deal about the gadgets you use every day.

[!NOTE] The official KTBS corrigendum renames this chapter from the printed heading "Cellular Mobile Phone Network" to "Modern Communication Systems", and re-titles Section 13.1 as "Cellular Mobile Phone Network: Introduction". We follow these corrected titles throughout.