CHP. 6 TELECOMMUNICATIONS

AGENDA -Will review Power point as a class -Students will answer questions on the index cards with your partner -Each student will create (3)questions about telecommunication and write them on (1) index card

Why is learning about Telecommunications important to your everyday lives? -It benefits and enhances the whole world market by creating a fast community and allowing for quicker reaction time and exchange of information. -Telecommunications have improved people's ability to stay in touch with friends and family. -People can access hundreds of television stations with the push of a button, getting instant access to information. -Telecommunications has also changed the way in which people work. It is now possible to commute from a beach in Florida, from home, or from anyplace where a computer, a phone or Internet service is available.

Telecommunications: -Communications over a long distance -Sending and receiving of messages -Telecommunication Devices: -TV -Phone -Radio -Satellite

History of Telecommunications: -Pony express -Smoke & Fire Signals -Telegraph -Invented by Samuel Morse -Began telecommunications in America -Send electrical pulses over a wire -Based on electricity and magnetism -Changed American society and economy

Telephone -Alexander Graham Bell & Thomas Watson -Elisha Gray – Applied for patent 2 hrs. later -Patent: A government document granting exclusive right to produce or sell an invented object or process for a specified period of time -Granville Woods improved on Grahams device

Cell Phones: -Transceiver : Transmitter and receiver combined into a single unit -Encrypt: Digital tech makes it easy to code or scramble electronic signals -Completey digital: PCS-Personal Communications Services -Like cellular, PCS is for mobile users and requires a number of antennas to blanket an area of coverage. As a user moves around, the user's phone signal is picked up by the nearest antenna and then forwarded to a base station that connects to the wired network. -PCS operate in the "1900 MHz band" (specifically 1850-1990 MHz) (frequency) -Cellular networks in the "850 MHz band" (specifically 800-894 MHz) (frequency) -Frequency: The number of radio waves or sound waves that pass any point per second:

How Communication Signals Travel -Copper Wire -Old Style – Not for new communications -Can carry a few dozen circuits -2 thin twisted copper wire -Coaxial Cable -Can carry a bigger load -Has a copper outer-tube -Center conductor is copper -Several cables bundled and covered in lead and plastic

How Communication signals travel Optical Fibers -Carry telephone & computer data -Carries thousands of voice and data circuits -Thin, flexible fibers of glass -Thickness of human hair -Glass carries signals in the form of light pulses -Surrounded by reflective cladding -Outside protective cover -FAST -Light pulses changed back to electrical signals

How Communication Signals Travel -Electromagnetic Waves -Waves created by electric and magnetic fields -Travel through the air -No wire connection needed -Can carry phone conversations over a long distance

How Communication signals travel Microwaves -Very short electromagnetic waves -In telecommunications, sounds waves are changed to microwaves -Waves are transmitted by an antennae -All waves have amplitude and frequency -Amplitude = Strength -Frequency = No. of waves in a sec.

How Communication Signals Travel Radio Waves -Electromagnetic -Longer than microwaves -Measured in hertz -Sound waves are combined with carrier waves then they are modulated (altered) -They are then amplified and transmitted -AM = amplitude modulation -FM = Frequency modulation

AM vs FM -FM based signal transmission consumes a higher amount of power than AM Amplitude modulation works between 540-1650 KHz while FM works at 88-108MHz. -During amplitude modulation the amplitude of the carrier wave is modulated as per the message signal. The other aspects of the carrier wave such as frequency remains constant. -During frequency modulation the frequency of the carrier wave changes while amplitude, remains constant. -FM has superior signal quality and consistently good reception -AM based signals are more susceptible to noise   -AM has problems with fading, which causes sound intensity to vary -Setting up an AM based radio communication system is very economical as there is no complicated circuitry and the processes are easy to understand. -FM is a fairly complicated communication system and requires high capital investment and expertise.

Radio -Evolved slowly -Supplies mass communication -No wire/No cables - (Radio forerunner) Gugliomo Marconi used electricity and electromagnets to create a telegraph w/o wire

-Analog signals are changed into electrical signals How Radio Works -Analog signals are changed into electrical signals -Then the low frequency sound signal is combined with the high frequency carrier signal -This combined signal is modulated to (FM or AM) -The modulated signal is amplified -The signal is transmitted by an antenna -Radio stations, CB radios, Pagers, etc. are all assigned their own frequency -A Radio picks up the sound on the frequency selected, with it’s antenna -A Radio separates the carrier waves from the sound signal (Called Demodulation) -A Radio boosts the sound signal and sends it to the speakers

Digital Radio Technology -Digital instead of analog transmission -DAB = Digital Audio Broadcasting -DAR = Digital Audio Radio -Transmits through existing radio frequencies -High Quality Sound -Digital radio signals make wireless connections between electronic devices possible (UWB – Ultra-wideband) -Digital radio reception is also much clearer than AM/FM, with no fuzziness, static or interference.

-Enormous impact on the public Television -Enormous impact on the public -Entertainment/Education/Information -Television is really a three-part invention: -The TV camera that turns a picture and sound into a signal -The TV transmitter that sends the signal through the air -The TV receiver (the TV set in your home) that captures the signal and turns it back into picture and sound. -TV creates moving pictures by repeatedly capturing still pictures and presenting these frames to your eyes so quickly that they seem to be moving.

How Television is Transmitted -Audio & video signal sent to antenna, cable, coaxial cable or satellite -Amplified and modulated like a radio signal -TV frequency higher than radio -TV receives signal -Audio and video signal gets separated -Audio gets sent to the speaker in TV -Video gets sent to the CRT (Cathode Ray Tube)

Digital TV -LCD (Liquid Crystal Display) is an electronically-modulated optical device shaped into a thin, flat panel made up of any number of color or monochrome pixels (a piece of an original image) filled with liquid crystals and arrayed in front of a light source (backlight) or reflector. It is often utilized in battery-powered electronic devices because it uses very small amounts of electric power. -PDP (Plasma Display Panel)is a type of flat panel display common to large TV displays (32 inches or larger). Many tiny cells between two panels of glass hold an inert mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light. -HDTV (High-definition television) is a digital television broadcasting system with higher resolution than traditional television systems (standard-definition TV, or SDTV). 10 times more picture detail than analog TV screens.

Difference between analog and digital TV -Analog TVs are restricted to analog signals while Digital TVs can process digital signals and analog signals. -Analog signals are prone to the problems like noise, interference, and even distorted displays -Analog TV sets use cathode ray tubes as their display while digital TV sets use flat panel display like LCD, plasma, or LED

Satellite Communication System -Developed in the 1960’s -Device placed in the Earth’s orbit (22,300 mi) above earth -Satellite stays in the same orbit (geostationary orbit) -Receive messages from 1 place and transmits to another -Satellite called “mirror in the sky” -Greatly influenced communications (instant communication)

How Satellite Communication Works -Satellite Communication Systems have earth stations and satellites -Earth Stations are also called Ground Stations -Earth Stations have large pie shaped antennas -An Earth Station receives signals & transmits to a satellite(Uplink) -Satellites receive signals and transmit to a Earth Station (Downlink) -Signals are coded so that the messages are received by the correct parties (The code directs the signal to the correct party) -Signals may be scrambled so only a certain station will receive and decode messages

SUMMARY -Telecommunications = Communications over a long distance -Telegraph was the beginning of telecommunications in American -Telegraph based on electricity & magnetism -Samuel Morse invented the telegraph/Uses Morse Code -Alexander Graham Bell invented the telephone -Telephone based on electrical signals, sound vibrations, and magnetism -Optical fibers are thin flexible fibers of glass that carry telephone and computer data -Optical fibers carry signals in the form of light pulses (FAST)

SUMMARY -Communication signal travel by electromagnetic waves -Electromagnetic waves make wireless tech possible -All waves have amplitude and frequency -Amplitude is the strength of the signal -Frequency is no. of waves in a sec. -Microwave and radio waves are electromagnetic -Radio waves are measured in hertz -How radio works: -Analog sound to electrical signal -Electrical signal combined with carrier signal -Signal is Modulated -Signal is Amplified -Signal is Transmitted -A radio receives the signal and demodulates (separates the carrier signal from the sound signal) -Electrical signal turned back into sound

SUMMARY -AM radio has lower energy consumption but is susceptible to noise -FM radio has superior signal and quality -How TV works -A camera turns a picture into a electrical signal -Signal is modulated -Signal is amplified -Signal is transmited -Signal is turned back into a picture by TV -A CRT is a Cathode Ray Tube/found in analog TV -HDTV is high definition TV (digital) -Satellites stay in a geostationary orbit

SUMMARY -Satellites receive and transfer messages from one place to another -A satellite system consists of ground stations and satellites -An uplink is when an earth station receives signals & transmits to a satellite -A downlink is when a satellite receives a signal and sends it to a earth station