The first kind of telecommunication system was designed and developed for the public switch telephone network of the PSTN. It was used for voice communications. This simple mode of voice communication has expanded and is now one of the most rapidly growing fields of work in the world.
Originally the telecommunication systems used low tech equipment and wires. It included old fashioned telephony and copper wires. These are quickly becoming obsolete. Better substitutes have been found which not only give better results for the existing services but make entirely new services possible. Together with voice communication, now we have video telephony, text messaging, emails, multimedia messaging, cable TV and many more.
With the coming of optical fibers the power consumption has become very less and audio as well as video signals can be transported over large distances. Optical fibres carry these signals in the form of light pulses. This was not possible before, as light could not be bent around corners. Optical fibers have a high refractive index which enables them to carry light around corners.
After optical fibers the next revolution was brought around by wireless networks. There wireless networks made it possible to transfer data over the air without the use of any kind of medium in between. All they need is a transmitter and a sensor. Mobile telecommunication systems are a good example of such networks. It has a very wide range. The wifi is another kind of wireless network which helps in exchanging data and sharing internet facilities. It has a relatively lesser range than that of a mobile network but provides a hoard of new possibilities.
The internet was probably the one biggest invention in history, second only to invention of wheel or the discovery of fire by prehistoric man. It made telecommunication systems a wider and more complex field than a human brain can imagine. There are different kinds of networks which can support and share an internet connection, like WAN, MAN, LAN etc.