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Telegraph
Invented by William Cooke and Charles Wheatstone in London. It transmits messages by hits which produce a sound and the messages are coded in Code Morse. When you press the telegraph it sends an electric current to the receiver that activates a magnet and attracts the lever (this produces the sound click). -
Experimental Telephone of Bell
Invented by Antonio Meucci, Elisha Grey and Alexander Graham Bell. Their prototype use a diaphragm and a wire that floated in acid to convert sounds in electricity and backwards, it can send messages and receives them. His objective wasn't just improving the telgraph, but to be able to talk with someone that wasn't there. -
Candlestick Phone
The main producers of these telephones were Western Electric, Automatic Electric Co., Kellogg Switchboard & Supply Company, and Stromberg-Carlson. The speaker and the headphone were spited. If you wanted to talk to someone, you just raised the headphone, talk to an operator that was in the phone central, gave her the number and she would communicate you with the owner of the number. -
Telephone disk
They first appeared in 1919. From the 1930 and after the speaker and the headphone were finally attached together in a piece called handset. In 1961, they stopped being analogue and they became digital, they also added buttons and suddenly almost every home had one. -
Cellular Telephone
At the beginning the cellphones were enormous and heavy and just worked to talk by the phone, but the quick technological advances, the phones have been shrinking, adding tons of gadgets (like the camera, music, games) until the newest iPhone, the iPhone X. -
How does it work now?
An analogic signal arrives to a local center. Then by the line, the call is converted into a digital signal to transmit it by a wire to the principal central. After that, through the air, the call is transmitted by a microwave bond to the central of the cell phones. Some centrals are bonded by wires. Finally the signal gets to the nearest cellphone tower by a wire. The signal gets to the phone by microwaves, and if the user is moving, the signal changes to the nearest cellphone tower.
