ELECTRONIC COMMUNICATION

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ELECTRONIC COMMUNICATION
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Electronic Communication

• Three parts Transmitter, Receiver and Channel
• Channel uses electrical energy
• Graphic communication electrical energy
• Electronic communication Information age
• Steam engine Industrial age
• Channel can be air or cables
• Systems sending messages immediately are
  Transmitting and Receiving Systems
• Systems storing messages electronically are
  Recording Systems

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Transmitting ReceivingSystems

• Telegraph
• The first electronic communication system
• F. B. Morse built a telegraph line in 1843
• The first telegraph cable was laid across
  Atlantic Ocean in 1858
• Telegraph system Key, Power source, Sounder and
  Wires --- Morse Code

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Transmitting ReceivingSystems

• Telephone
• Graham Bell was a teacher of the deaf
• A telephone mouthpiece contains tiny carbon
  grains
• Louder speech --- grains are tightly packed
• Soft speech --- grains are loosely packed
• The amount of the current flow changes as we
  change the way we speak
• A thin piece of metal vibrates in the earpiece on
  the receiver
• Amplifiers, repeaters are needed for the long
  distance transmission to increase the electric
  current
• Connection b/w two telephone --- Telephone
  Switching --- Digital to Analog conversion

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Transmitting ReceivingSystems

• Telephone
• Fiber optic --- 10,000 conversations, Microwave
  --- 1000 conversations
• Digital technology --- forwarding, waiting, voice
  synthesizer
• Cordless phone --- transmission to a nearby
  telephone
• Cellular phone --- radio wave --- particular area
• Automatic telephone switching --- Strowger
  switches

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Transmitting ReceivingSystems

• Radio
• Maxwell --- signals can be sent through air
• Marconi heard the three shorts of the Morse Code
  for the letter S, sent across the Atlantic
• Regular radio broadcasts began in the 1920s ---
  antennas
• Radio lets us listen to music, news and sporting
  events and also provides us a mode of two way
  communication
• Alternating voltage is sent to an antenna --- an
  electromagnetic wave is launched into the air
• Low frequency --- high wavelength and vice versa
• Wave length speed of the wave / frequency of
  the wave

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Transmitting ReceivingSystems

• Radio
• High frequency (HF) radio waves bounce off the
  atmospheres upper layer, the ionosphere --- for
  two points on the earth
• Super high frequency (SHF) radio waves are used
  for satellite communication
• The channel is the part of the electromagnetic
  spectrum used for the signal
• One transmitter, many receivers --- broadcasting,
  e.g. FM AM
• One transmitter, one receiver --- point to point

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Transmitting ReceivingSystems

• Television
• Much like the radio except that the transmission
  can be seen also
• Video camera is needed at the transmitting
  station and a monitor at the receiving station
• Video signals may be stored --- VCR
• Color signals break down light into red, green
  and blue
• Cable TV, Pay per view

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Transmitting ReceivingSystems

• Microwave Communication
• Microwaves are radio signals that use higher
  frequencies than FM radio signals or TV
  broadcasts
• Used for telephone and TV signal transmission
• Frequency distribution for different uses on page
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• Satellite Communication
• They are radio relay stations called repeaters
• They have to be geosynchronous
• Uplink and downlink