The TelegraphThroughout history, there have been many versions of the telegraph. It was first demonstrated in 1835 by Professor Moncke in Germany. Another version was developed in 1837 by William Cooke which could transmit a signal as far as 1.6km away. The Morse Code was then developed in 1844 by American Samuel Morse, which used a series of dots and dashes to send messages 60 kilometres away. As a switch on the telegraph was opened and closed, the dots and dashes were transmitted onto paper or converted into sounds which were read by a translator. The first telegraph table was established in 1851 across the English Channel and another was laid across the Atlantic Ocean in 1858 however t ...view middle of the document...
The inner core carries analogue and digital signals while the outer layer protects the core from interference and reduces attenuation (loss of signal strength). The first coaxial cable in Australia connected Sydney, Canberra and Melbourne in 1962.Optical FibresAn optical fibre is a very thin tube or strand of glass which was first developed in the 1930's. Optical fibers play a prominent role in the global communications network. The tube uses total internal light reflection where voice, fax or computer data are converted into an electrical signal and is then turned into pulses of light being proved by a laser. Laser light is coherent (same frequency and wavelength) resulting in a powerful beam which can carry a large amount of data with little dispersion. Sydney and Melbourne are linked with over 1.5 kilometres of optical fibre.Deborah White 10BMicrowavesMicrowave links are used to send signals through the air from repeater station to repeater station. Microwaves travel in a straight line so all stations must be in lined with each other. Microwaves are used to connect satellites for long-distance communication as well as being use din the mobile phone network. The first microwave link in Australia was created in 1959 between Melbourne and Bendigo.Mobile PhonesMicrowaves are used to transmit digital signals within a network of regions (cells) for mobile phones. When a mobile is turned on, a signal is sent to the network which registers its location. As the location of the phone changes, the cell with the strongest signal registers the phones location and send its to the exchange. When a call is made, the exchange detects the location of the receiving phone and sends the call to the base station in the nearest cell. All base stations every 50 kilometres to strengthen weak signals.The RadioThe AM broadcast radio is used to send voice and music messages at a medium frequency on the radio spectrum. AM radio uses "amplitude modulation" where louder sounds at the microphone makes wider sound waves in the transmitter power however the transmitter frequency remains unchanged. Transmissions are affected by static because lightning and other sources of radio add their radio waves to the ones from the transmitter. The Amplitude Modulated (AM) radio was invested by Reginald Fessenden and Lee de Forest so that more than one station can send signals in 1906.The FM broadcast radio is set at a much higher frequency than the AM radio. The FM radio uses frequency modulat...
