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How Telephone Works Present by: Chongbo You SeungJae Baek Qihui Yu.
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Transcript of How Telephone Works Present by: Chongbo You SeungJae Baek Qihui Yu.
How Telephone Works
Present by:Chongbo You
SeungJae Baek Qihui Yu
Description
Telephone
• It is one of the most important inventions 1800s and an useful tool of daily communication among people.
• Technology of telephone developed dramatically since the invention. Improvement of technology changed people’s life considerably.
• The functions of telephone became more and more various.
• In the 1870s, there were two
inventors for telephone, Elisha
Gray and Alexander Graham
Bell. They debated over the
invention of telephone and
Bell has won. Bell’s telephone
was based on telegraph
technology.
• The first telephone sent
signals to the air pressure of
the original sound and when
the voice passes the
transmitter, it changes into
variable electric current.
History and Development
Alexander Graham Bell's Telephone Patent Drawing, 03/07/1876.
• Soon Thomas Edison invented two
most important inventions. He
developed the first commercially
practical transmitter and receiver.
• Edison also invented carbon
microphone which produced louder,
cleaner signals travelling longer
distance.
History and Development
• In 1880s, there were no dial pads or the ring tone.
They had to contact the operators and the
operators were usually women who are pleasant.
• By 1900 the rotary dial was developed and slowly
placed into the phones. Slowly improvements
were made in quality of service and calling
capacity. Radio telephone links created the first
long distance service between England and the
U.S. in 1927.
History and Development
• The first computerized switchboard was put into
service in 1976. Furthermore, coaxial cables were
placed in 1940s that reduced interference and
increased calling capacity for the ever expanding
telephone system.
• Digital transmission was introduced in 1962. In
the old analog system, the electronic signal in the
wire looks like the sound waves in the air.
History and Development
• As technology continue to improve, telephone becomes smaller and smaller. Telephone develops into cellphones becoming portable.
• Cellphones are convenient and easy to operate. It becomes a trend to have cellphones.
• The functions of cellphones expand significantly. It not only can communicate by making calls and sending messages, but also can search on the Internet and use various applications.
History and Development
How Telephone Works
In order to understand how
telephone works, we will introduce
you the simplest phone structures,
and the functions and basic principle
of each part.
How Telephone Works
Basic Parts of a Telephone:• Speaker• Microphone• Hook Switch
From HowStuffWorks.com
How Speaker Works
How Telephone Works
Speaker: • Use a permanent magnet to transfer
electric signal to acoustic signal• Process:
Charge the voice coil inside speakerGenerate magnetic field around the coilChange directions of electrical current in the coilCoil’s polar orientation reversesMagnetic forces move coil and attached diaphragm back and forth
How Microphone Works
How Microphone Works
Microphone:• Use carbon granules compressed
between two thin metal plates and magnets to transfer acoustic signal to electric signal
• Process: Voice causes carbon granules to compress and decompress
Status of carbon granules changes resistance of the granules
Current flowing though microphone will modulate
How Telephone WorksHook Switch:• To connect and disconnect the phone
from the network• When one lifts handset, hook switch will
connect the network. When one puts the phone down, hook switch will disconnect the network.
How Telephone Connects Us
After introduced what’s inside the telephone, now it’s the
time to know the how the external parts work with it:
• The copper wire that is connected to the phone jack inside
our house is from the box down the road.
• Assume that we have two separate pairs of telephone lines,
then second pair is usually colored yellow and black inside
our house.
• Then what connect between the wire that comes from our
home and the local telephone company? It is a thick cable
packed with 100 or more copper pairs. We are going to
talk about it next.
• The picture shows a typical street box in
the southwestern, US.
• The green box is basically a place where
the 50-pair cable pops out and stretch out
through the underground so that a phone
company workers can splice into it.
Digitalizing and Delivering
• When we trace all the way to the phone company through the
wire, we met the concentrator which digitizes our voice at a
sample rate of 8,000 samples per second and 8-bit resolution.
• It then combines our voice with others and sends them all to a
single fiber-optic cable to the phone company office.
• Let’s say if we are calling someone who are connected by the
same office, then the switch simply creates a loop between your
phone and the phone of the person you called.
• Once the sound is digitized, the signal will be transferred to a
local exchange house, where the digital signal will delivered to
the other side of the recipients’ home.
Reference
• Brain, Marshall. “How Telephone Work”. HowStuffWorks.com 01 April 2000. Web. 02 December 2011.http://electronics.howstuffworks.com/telephone.htm
• Bruce, Robert V. Bell: Alexander Graham Bell and the Conquest of Solitude. Cornell University Press. 1990. Print.
• Coe, Lewis. The Telephone and Its Several Inventors: A History. McFarland, North Carolina. 1995. Print.
• Josephson, Mattew. Edison: A Biography. Whiley. 1992. Print.
Thank you!