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EVOLUTION OF TELEPHONES, image, image, image - Coggle Diagram
EVOLUTION OF TELEPHONES
1ST TYPE: WIRED TELEPHONE
invented in the 1800's:
Alexander Graham Bell
HOW IT WORKS
STEP 1
: when the caller digits a number on a telephone keypad, each key generates a combination of tones, where they are transformed in electrical signals
STEP 2
: the signals are carried in the local telephone exchange where the electronic switching system recognises the tones and directs the call towards the destination
nowadays copper wires are replaced with optic fiber
it can carry much more data
first appearance: 19th century: tin can phone
acoustic speech-transmitting device that consist of two cuups attached together with a string or wire
when a person starts emitting sounds in ohne of the cup, teh string vibrates and carries this vibrations into the other cup
2ND TYPE: WIRELESS TELEPHONE
first appearance: 1980
cellular telephones use radio waves in order to communicate
HOW IT WORKS
STEP 1
: when a call starts, radio waves are sended to the antenna where the call found his origin
STEP 2
: a transmitter relays the waves to a mobile telephone switching centre which sends the call to another cellular phone
STEP 3
: to comunicate with a home phone the mobile switching office directs the call to a local telephone centre an the signal enters the normal telephone network
