Alexander Graham Bell By Hannah Jennings And his Invention of the Telephone And his Invention of the Telephone

Alexander Bell Born on March 3rd, 1847 in Scotland Educated the deaf 1878 invented the telephone 1878 founded the Bell telephone company

Alexander Bell Volunteered for the deaf for many years Earned the Volta Prize for his invention Established the Alexander Graham Bell Association for the deaf Died on August 2nd, 1922

The Telephone Four Main Parts: 1). Dialing Mechanism 2). Transmitter 3). Ringer (inside) 4). Receiver 2). 4). 1). 3).

Dialing Mechanism On the handset, or base of phone Has set of buttons or keys called a key pad Older telephones had rotating keypad called rotary dial The computer recognizes the tone each key produces, and dials it

Dialing Mechanism

Sending Signals The speaker’s voice travels through an electric current The current goes from the transmitter to the hook switch Then from there, it goes to the wall jack The wall jack sends the signal into the telephone network

Sending Signals To Wall Jack

Transmitter Modern phones use a foil-electret condenser transmitter (a type of microphone)

Transmitter The circular diaphragm is stretched over a hollow back plate Diaphragm Backplate

Transmitter The diaphragm touches the back plate only in some places Diaphragm

Transmitter When the diaphragm vibrates, it condenses the air, and that influences the electric field Electric Field

Transmitter When the electric field changes, it changes the electric current that is sent into the network To Telephone Network

Variations in current “copy” the speaker’s voice, and send the current through a wire Transmitter

Ringer Signals incoming calls Early Phones had small bells Modern phones are replaced with a computer chip that makes a sound

Receiver Converts electric current into sound through a speaker

Receiver When pulses of electric current come through the wire coil, a magnetic force is created, which moves the magnet Wire Coil Magnet

Receiver The magnet vibrates the diaphragm, which creates sound waves to duplicate the speaker’s voice Diaphragm

Receiver Speaker Wire Coil Magnet Diaphragm

Telephone Networks Signal leaves the house and goes to a telephone box

Telephone Networks From the box to the telephone pole, and from the pole to the local exchange

Telephone Networks An exchange is a building that is connected to all the telephone poles in the area. It connects the incoming call with the number that was dialed

Telephone Networks From the local exchange, to the main exchange, from there to the international exchange The main and international exchanges serve the same purpose as local, except they are connected to the smaller exchange buildings It then goes in the backwards order to the other telephone

Telephone Networks Telephone Boxes Telephone Poles Local Main

Cell Phones Mobile devices that transmit and receive radio signals Communicates through an antenna transmitter Transmitter serves a single geographic area called a cell

Cell Phones The cell connects with a regular telephone network It has the same basic parts of a telephone

Telephones in Remote Areas Too expensive to run wires to low populated areas BETRS fills in the “gap” (Basic Exchange Telephone Radio Service) Each house has a transmitter that sends radio signals to the telephone exchange

BETRS Telephone Transmitter Radio Signals Telephone Exchange

About the Author I am Hannah Jennings. I did the telephone because I like to talk on it. I am 12 years old, and in the 7th grade. I live in Winston- Salem, North Carolina.

Bibliography “Alexander Graham Bell- Biography.” What you need to know ABOUT. June, /26/ bltelephone2.htm. Brian, Marshall. “How Telephones Work.” How Stuff Works. 4/29/ telephone.htm

Bibliography Brodsky, Arthur. “Telephone.” The World Book Encyclopedia.(volume 19) World Book Inc. April 27, Hounshell, David, A. “ Bell, Alexander Graham.” The World Book Encyclopedia (volume 2) World Book Inc. April 27,2004.