Different useful application areas under modern electronic communication are presented in brief. In telephone switching, the benefit of central switching is discussed followed by function of a simple exchange and hierarchy of switching offices. The idea of space-time switching and time slot interchanging is introduced and their usefulness discussed. In computer communication, it is described how computers are connected with each other by different types of networks. Network protocols are discussed and concept of LAN, MAN, WAN, internet introduced. This also discusses digital interfaces like ISDN, ADSL, ATM, SDH or SONET. Basic concepts behind optical communication through fibre optic cables which provides huge bandwidth are presented. In satellite communication, various orbital paths are compared and role of LEO, MEO, GEO satellites discussed. Working of a C band satellite transponder is cited as an illustration of how satellite communicates to earth. Global Position System (GPS), a modern satellite based navigational aid is described. Elementary idea of RADAR based ranging that calculates the delay in receiving radio wave echo is presented. Use of RADAR in weather prediction is discussed in brief.
