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Waves and Communication. Unit 2: Energy and Our Universe. Flash activity (these activities are not editable). Accompanying worksheet. Teacher’s notes included in the Notes Page. PLTS. For more detailed instructions, see the Getting Started presentation. What is the Morse code for SOS?.
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Waves and Communication Unit 2: Energy and Our Universe
Flash activity (these activities are not editable) Accompanying worksheet Teacher’s notes included in the Notes Page PLTS For more detailed instructions, see the Getting Started presentation
What is the Morse code for SOS? Wired communication Wired communication uses wires to carry signals from a transmitter to a receiver. The first wired communication system was the electric telegraph, invented by Samuel Morse in 1835. He used pulses of electric current to produce a series of dots and dashes on a strip of paper. He assigned each letter of the alphabet a certain pattern of dots and dashes, inventing ‘Morse code’. Morse code is still used today for radio communications and for communication between ships, where signal lamps are used to spell out the letters.
The invention of the telephone In 1876, Alexander Graham Bell patented the first method of transferring a person’s voice into electrical impulses that could be carried by a wire. According to the famous story, the first fully intelligible telephone call occurred on March 6, 1876. Bell used a receiver and transmitter of his own design to call his assistant (although he was only in the next room!). It is said that Bell refused to have a telephone on his desk, viewing his greatest invention as an intrusion on his work.
Case study: transatlantic telephone calls The first transatlantic telephone call was made in 1956, following the laying of telephone cable across the floor of the Atlantic ocean from Newfoundland to Scotland. The cable could carry 36 telephone calls at a time. Cables under the Atlantic ocean are still used to transmit international telephone calls, although the original cable hasn’t been used since 1978. The newest cables are fibre optic, which is relatively cheap and can carry a very large volume of calls. A single optical fibre can carry the digital signals for about 12000 phone calls!
The cable network Optical fibres are not only found in telephone networks. They are also used for connecting computers to one another and to the internet, and in the cable television network. At the headend, signals are received from broadcasters by satellite, antenna, or fibre optic cable. Nodes distribute signals to local homes. Signals are converted into optical signals and transmitted along optical fibres to nodes. Terminal equipment, such as set-top boxes, interpret the signals.
Optical fibres – the downsides? Optical fibres have changed the way people work and play, but is this necessarily a good thing? Should we be able to get films and music online for free? Can working faster and dealing with more information increase stress at work? Does having books and articles available on computers make it easier for students to cheat?
The discovery of radio waves Radio waves were discovered in 1888 by Heinrich Hertz (who gave his name to the units used to measure frequency: Hz). Hertz was the first person to send and receive radio waves. They were the first type of wave to be transmitted wirelessly. Many scientists at the time experimented with different ways of sending and receiving radio waves. Early radio wave transmissions consisted of Morse code. The first transmission of the human voice occurred in 1906. By the 1920s, regular radio broadcasts were being made in the UK.
ionosphere Why do some radio waves travel so far? Low frequency (up to 3MHz) radio waves travel along the Earth’s surface in the lower atmosphere. These ground waves are used for local and national radio. Higher frequency radio waves (3–30MHz) are reflected off the ionosphere high in the atmosphere. These sky waves are used for international and amateur radio.
The TV broadcasting network Most Freeview television programmes are transmitted from a broadcasting centre to a satellite in orbit around the Earth. The signal is relayed back down to transmitter towers, which transmit the signal to the local area, known as a cell. Satellite TV programmes are received directly by a satellite dish attached to a building, instead of being relayed through a transmitter tower.
What are some potential disadvantages? Case study: CCTV Closed-circuit television (CCTV) cameras are used for surveillance. Wireless CCTV cameras can be attached to lamp posts and buildings to monitor streets affected by antisocial behaviour, or people can buy them to monitor their own home or business. The images can be sent directly to a 3G mobile phone or laptop computer to be monitored. The advantage of this type of system is that cameras can be moved around, depending on where they are needed. This saves the cost of having to install a permanent CCTV system.
You are an electrical engineer for a large multimedia company that provides radio, television, telephone and internet services to its customers. The company is considering providing more wireless services. You have been asked to produce a report describing how waves are used in communications. Your report should include: • a description of how information is transmitted and received in wired and wireless forms, using some of the forms of media that the company provides as examples • a comparison of the advantages and disadvantages of wired and wireless communication.
