Wally is a slacker, he is always looking for the Wally is a slacker, he is always looking for the easy way out of doing anythingeasy way out of doing anything

The $100 computer?

AC vs DC CircuitsAC vs DC Circuits

DC and AC devices in everyday lifeDC and AC devices in everyday life

DC DevicesDC Devices• BatteriesBatteries• Automotive electronicsAutomotive electronics• Portable electronicsPortable electronics

IPodIPod Cellular PhoneCellular Phone PDAPDA

• Laptop computersLaptop computers• Desktop computersDesktop computers• Solar cellsSolar cells• Computer and memory Computer and memory

chipschips

AC DevicesAC Devices• Electric wall outletsElectric wall outlets• Household appliancesHousehold appliances• High voltage High voltage

transmission linestransmission lines• Electromagnetic Electromagnetic

transmissionstransmissions Mobile phone signalsMobile phone signals Satellite signalsSatellite signals Radio signalsRadio signals

AC Frequency AC Frequency

Number of complete cycles per unit Number of complete cycles per unit timetime

Units are hertz, HzUnits are hertz, Hz Units are cycles per secondUnits are cycles per second Household electrical outlets operate Household electrical outlets operate

at 60 hertz or 60 cycles per secondat 60 hertz or 60 cycles per second Electromagnetic waves operate at Electromagnetic waves operate at

much higher frequenciesmuch higher frequencies

Heat lamps

Sun burn

Broadcast FrequenciesBroadcast Frequencies Use of frequencies for broadcast are controlled by the Federal Use of frequencies for broadcast are controlled by the Federal

Government – the FCC - Federal Communications CommissionGovernment – the FCC - Federal Communications Commission License required to use a given frequencyLicense required to use a given frequency Companies purchase licenses to use these frequenciesCompanies purchase licenses to use these frequencies Specific bands are setup for all transmissionsSpecific bands are setup for all transmissions

• Police/Fire/EMS radioPolice/Fire/EMS radio• Commercial aircraftCommercial aircraft• Marine radiosMarine radios• Mobile phonesMobile phones• Military applicationsMilitary applications• Citizen band radioCitizen band radio

One notable exception is the Unlicensed Band (ULB) at 2400 MHz or 2.4 One notable exception is the Unlicensed Band (ULB) at 2400 MHz or 2.4 GHzGHz

• Microwave ovensMicrowave ovens• Cordless phonesCordless phones• Bluetooth devicesBluetooth devices• Wi-Fi devicesWi-Fi devices• Any new device can use this frequency provided it follows set specifications on Any new device can use this frequency provided it follows set specifications on

power, range, and data transmission ratespower, range, and data transmission rates

Some common frequenciesSome common frequencies AM RadioAM Radio

• 535 to 1605 KHz 535 to 1605 KHz FM RadioFM Radio

• 88-108 MHz88-108 MHz Broadcast TV (not cable TV transmissions which are not Broadcast TV (not cable TV transmissions which are not

broadcast but sent via a wire)broadcast but sent via a wire)• Channels 2-4 54-72 MHzChannels 2-4 54-72 MHz• Channels 5-6 76-88 MHzChannels 5-6 76-88 MHz• Channels 7-13 174-216 MHzChannels 7-13 174-216 MHz• Channels 14-36 470-608 MHzChannels 14-36 470-608 MHz• Channels 38-69 614-806 MHzChannels 38-69 614-806 MHz

Older “analog” phones - 824-894 MHz Older “analog” phones - 824-894 MHz PCS digital phones - 1850-1990 MHz – PCS digital phones - 1850-1990 MHz – Current frequency of Current frequency of

operation of most mobile phonesoperation of most mobile phones Bluetooth and Wi-Fi devices - 2400-2497 MHzBluetooth and Wi-Fi devices - 2400-2497 MHz GPS – 1575.42 and 1227.60 MHzGPS – 1575.42 and 1227.60 MHz RFID – multiple frequencies – 860 to 960 MHz very commonRFID – multiple frequencies – 860 to 960 MHz very common

Assignment due next classAssignment due next class

HW #2 from the web siteHW #2 from the web site• Write a one page report on “How a Write a one page report on “How a

Cellular Phone System Works”Cellular Phone System Works”• Why is it called “cellular”?Why is it called “cellular”?• Is it really a phone or something else?Is it really a phone or something else?• Be sure to include the frequency of Be sure to include the frequency of

operation on current cellular phonesoperation on current cellular phones• Include at least two referencesInclude at least two references