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ELECTRONIC COMMUNICATION

ELECTRONIC COMMUNICATION. 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

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ELECTRONIC COMMUNICATION

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  1. ELECTRONIC COMMUNICATION

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. Transmitting & ReceivingSystems • Radio • High frequency (HF) radio waves bounce off the atmosphere’s 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

  8. 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

  9. 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 177 • Satellite Communication • They are radio relay stations called repeaters • They have to be geosynchronous • Uplink and downlink

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