Book+2+Chapter+4+Lesson+2

II. Electronic Communication A. 1st Telegraph Message - 1844 B. Telephone - 1876 - Alexander Graham Bell 1. 3 parts i. Transmitter ii. Receiver iii. Dialing Mechanism 2. Sound Transformed into an electronic signal that is transmitted and then transformed back into sound 3. Transmitter - sound transformed into an electric signal i. Sound travels as a wave ii. Waves cause metal disk in the microphone to vibrate changing sound into electric signals iii. Travels through a series of switches and wires 4. Receiver - uses a speaker to transform the electronic signal back into sound i. In earpiece ii. Speaker made up of electromagnet and thin metal disk iii. Electric current varies with signal strength iv. Disk vibrates in pattern to electronic signal into sound waves 5. Dialing mechanism 0 sends series of pulses or clicks to the switching network. Push button - tones C. Sound Recordings 1. Communicate information using electronic signals 2. Can be reproduced using analog or digital device 3. Analog - Phonograph, record I. Waves/ridges on record ii. Needle plays recording iii. Red into an amplifier and then into a speaker 4. Digital - CD player, CD I. Pits - Microscopic holes ii. Flats - level areas between pits iii. Beam of light read it iv. Fed into amplifier and then into a speaker D. Electromagnetic Waves 1. Carry electronic signals over long distances 2. A wave that consists of moving or changing electric and magnetic fields 3. Do not need to travel through matter 4. Ex. light, microwaves, x-rays 5. High points - crests 6. Low points - troughs 7. Amplitude - height from the center line to a crest or trough 8. Frequency - the number of waves passing a given point each second 9. Carrier Wave - changed or modulated amplitude of frequency of a wave 10. Analog Signal - Strength or amplitude of electric current changes 11. Modulated in 2 ways i, Amplitude modulation (AM) - change the amplitude of the carrier wave to match that of the signal ii. Frequency modulation (FM) - change the frequency of the carrier wave to match the amplitude of the signal - space between the waves varies with the strength of the signal E. Radio 1. Voice or music on an AM or FM radio station are electronic signals carried by an electromagnetic wave 2. Transmission i. Radio station sends sound in electronic signal ii. Analog signal - audio waves then a transmitter amplifies them iii. Audio signal combines with carrier wave this sent out over antenna 3. Reception i. Radio - antenna gets the wave on a specific frequency and you tune in - radio separates audio signal/wave, the speaker transforms into sound F. Television 1. Electromagnetic waves can carry images and sound 2. Transmission - same as radio - sent by antenna, cable network or communication satellite 3. Reception - same as radio 4. Television screens i. Cathode ray tubes ii. Plasma iii. LED

Quiz 1. Audio only 2. Yes 3. Camera and microphone 4. Speaker 5. Transmitter, receiver, dialing mechanism. Transmitter - mouth piece - sound into electrical signal; receiver - earpiece - electric signal into sound; dialing - tells switching system where calls go 6. A phonograph or digitally like CD 7. Wave B is AM; Wave A is FM 8. Amplitude 9. Consists of electric and magnetic fields. Can carry signals long distances 10. Number of waves passing a given point each second

Study Guide 2. Compact disc 3. Electric and magnetic fields 4. Transforms sound into an electronic signal 17. True 18. False - Frequency 24. Both TV's and radios and electronic devices that separate electronic signals from electromagnetic carrier waves. Both have receivers and speakers. TV also gets video - both have audio 26. It's not a TV because it has no way to transform a video signal into a image. Its not a telephone because it can't transform sound into an electronic signal or to transmit a signal 27. Radio doesn't have receiver antenna which receives electromagnetic waves from radio stations. Waves carry signal that radio speakers transforms into sound 28. Digital - it has a pulsing signal