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Published byBrice Fletcher Modified over 9 years ago
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TELECOMMUNICATION
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Communication over a long distance.
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How the Telegraph Works
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Sends electronic pulses over wire
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Consists of: – Battery – Key (sender) – Wire – Sounder (receiver)
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How the Telephone Works
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Sound waves cause vibrations.
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Transmitter – microphone that uses a diaphragm and carbon granules to produce a varying electrical current
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Receiver – the microphone in reverse
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Electronic telephones Cellular telephones (pages 126-127)
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Transmission Channels
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Copper Wire
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Coaxial Cable
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Optical Fibers
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Microwaves – very short electromagnetic waves
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Radio Waves – Amplitude: strength of the wave – Frequency: number of waves that pass a given point in one second
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Radio
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How Radio Works
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Antenna picks up waves that have the station’s frequency.
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How Television Works
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Broadcast television signals are sent to an antenna.
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The tv receives the signals and converts them to electrical signals.
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The video and audio signals are separated.
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Satellite Communication Systems
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a device placed in orbit above the earth to receive messages from one location and transmit them to another
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Geostationary orbit: 22,300 miles above earth traveling at the same speed as the earth rotates.
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How the System Works
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Signals are sent to orbiting satellites through earth stations.
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Uplink: it receives signals and transmits them to the satellite.
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Downlink: the satellite receives the signals and transmits them to another location back on earth
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