Science of Waves and Modern Telecommunications

Understanding Waves and Communication

Waves are the means of transmitting various communication systems like radio and telephony. A wave is a disturbance of space that travels without carrying matter, but it does carry energy. For example, throwing a stone into the water creates waves.

Types of Waves

Mechanical Waves

Mechanical waves are those that require a material medium to propagate, such as sound or the agitation of a string. Thus, sound travels faster through solids, then liquids, and then air, but it cannot travel through a vacuum.

Electromagnetic Waves

Electromagnetic waves can propagate through a vacuum and also through some materials. Heinrich Hertz invented the means to detect them in 1887. These waves travel at the speed of light and include light, television, and radio signals.

The Electromagnetic Spectrum

The set of all electromagnetic waves and all possible wavelengths is called the electromagnetic spectrum.

Telecommunications Systems

Telecommunications comprise several systems capable of producing electricity and quickly sending visual, written, or voice messages. Among such systems are telegraphy, telephony, and by extension, radio broadcasting and television.

Telegraphy

The first telegraphs transmitted electrical impulses, either long or short (dashes or dots), via a cable to a receiver. The telegrapher interpreted the signal. When in 1901 Marconi sent radio signals in Morse code from one side of the Atlantic Ocean to the other, it became radio telegraphy or wireless telegraphy. It is currently broadcast via telegraphic terminals connected to networks like the Internet.

Telephony

A basic telephone consists of a microphone, a headset (speaker), a ringer, and a keyboard. In most modern phones, there is a microchip that allows for the encoding and digitization of voice signals.

1. The sound waves from speaking vibrate a membrane in the microphone. The components of the microphone convert the vibrations into electrical signals.
2. The electrical signal is transmitted by a cable to a telephone central exchange.
3. The signal travels between telephone exchanges and reaches the receiver via a cable.
4. An amplifier increases the volume of electrical signals and sends them to the headset, where electrical signals are transformed back into sound.

In landline phones, the headset and microphone are connected to a base. Mobile phones have a radio transmitter and receiver system in the microwave band.

Television

A television works through a process that converts electromagnetic waves into a quick sequence of images that reproduce reality. Traditional TVs (CRT) have a cathode ray tube with three electron beams; each beam strikes the point of the corresponding primary color phosphorescence. By the action of copper coils, electron beams perform continuous and fast sweeps of the screen in a manner similar to the human eye reading a page from left to right in each line and up and down in the 625 fields of the display, at a rate of 25 images per second (creating a clear picture) due to the persistence of images on the retina. LCD televisions contain liquid crystal molecules.