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How Cell
Phones Work
Mollie Safran, Timothy Rundle
Before Cell Phones
-Before Cell Phones, people had to use
radio-telephones
-the radio-telephone needed powerful
transmitters that connect to one tower per
city
-the radio-telephone could only have a few
per city because of limited channels
THE CELL PHONE!
-The cell phone splits up cities into CELLS so more
people can talk at once
-Limited number of frequencies available without the
use of cells
-Not perfect! Think about phones not working in
Beaver Stadium
-Full-duplex system
-One frequency is used for listening and another for
hearing
How should you ask your friend to Prom?
I’ll call!
dial the phone!
your call will go by
radio waves to the
transmission tower
in your cell
your call gets sent to the Mobile
Telephone Switching Office where
it is redirected to wherever your
friend is
Getting Connected
-Cell phones send waves (specifically radio waves) at a particular
frequency (f=1/T) to reach another cell phone
-Emitting Electromagnetic Radiation (EMR) which is always in
phase (constructive interference)
-Electromagnetic radiation emits waves of electric and magnetic
energy which travels the ‘speed of light’
-Cell phones take voice and turn it into a continuous sine wave
New Insight
-We’ve learned many of the consequences of
cell phone wave radiation
-Tissues nearest to the radiation can absorb
the energy
-You’re holding it against your head!
-Exposure to non-ionizing radiation is known
to cause cancer
New Insight
-The number of cell phone users in the world
has increased at an alarming rate in
recent history
-forced a need for substantial changes
in cell phone technology
-Just think about how far cell phone
technology has come so quickly and think
about where we might be in ten years!
Bibliography
"How Cell Phones Work." HowStuffWorks. N.p., n.d. Web. 19 Mar. 2014.
"How Do Mobile Phones Work?| Explore | Physics.org." How Do Mobile Phones Work?| Explore | Physics.org. N.p., n.d.
Web. 18 Apr. 2014.
"Cell Phones and Cancer Risk - National Cancer Institute." Cell Phones and Cancer Risk - National Cancer Institute. N.p.,
n.d. Web. 19 Apr. 2014.
"HowStuffWorks "How Cell-phone Radiation Works"" HowStuffWorks. N.p., n.d. Web. 20 Apr. 2014.
"Electromagnetic Radiation." Wikipedia. Wikimedia Foundation, 20 Apr. 2014. Web. 20 Apr. 2014.