Telephones and Cellphones

Telephones and Cellphones — page 1 — Introduction At the touch of a button we can use a modern telephone to talk to another person just about anywhere on Earth We could also use it to send pictures and written messages and even see the face of the person we are talking to All this technology which can ﬁ t into one pocket-sized gadget did not exist 150 years ago Back then communication was a great deal slower A DIFFERENT VIEW MARATHON Today marathons are long-distance running races but the first one was run to send a message In 490 B C the Greeks won a battle at a town called Marathon Pheidippides a messenger ran 26 miles and 385 yards 42,195 m all the way to Athens with the news This has been the distance of every marathon ever since 4 Sealed Letters Until the 1800s most communication was by letter To ensure a letter was not read until it arrived at its destination the sender sealed it with wax He or she pressed down the soft wax with a ring or other personal object to show who it was from

Telephones and Cellphones — page 2 — Code Down a Wire The telegraph was invented in 1837 It sent written messages by wire Tapping a key switched an electric current on and off to create coded electrical signals for every letter of the alphabet Waving Flags Brightly colored ﬂ ags are still used to send messages between ships using a code called semaphore A signaler holds two ﬂ ags in speciﬁ c positions that represent a letter or number and spells out words to anyone who can see him from on-board another ship At night the ﬂ ags are replaced with glowing sticks 5

Telephones and Cellphones — page 3 — Connecting In March 1876 the American inventor Alexander Graham Bell made the ﬁ rst telephone call to his assistant Watson come here I want to see you CONNECTORS were attached to wires which sent the signal to another telephone L ike any sound a voice is a vibration in the air Bell’s telephone converted those vibrations into an electrical signal and then back into sound Large Box Telephone This early telephone was built by Bell in November 1876 It used magnets to make an electric current vibrate like a sound wave The current was sent from one telephone by wire to a second telephone where it electriﬁ ed the magnet making its magnetic ﬁ eld rise and fall with the signal The magnet pushed and pulled on a metal disk which vibrated the air and recreated the sound of a voice A HEAVY WOODEN BASE kept the phone still to reduce unwanted vibrations A MAGNET converted the vibrations of the metal disk into an electrical signal TIMELINE 1667 String Telephone English scientist Robert Hooke shows that sound waves can travel along a tight wire A tin can telephone right works using this system 6 1849 Talking Telegraph Antonio Meucci an Italian inventor experiments with electric shocks used to treat stiff joints He uses them to transmit a voice signal into the body so it can be picked up by the ears

Telephones and Cellphones — page 4 — A METAL DISK behind the mouthpiece vibrates when the sound of a voice hits it POWER PEOPLE ALEXANDER GRAHAM BELL Alexander Graham Bell made many demonstrations of his telephone A holding conversations with his assistant Thomas Watson back at the laboratory B Bell answered the telephone by saying Ahoy Another American inventor Thomas Edison suggested using Hello At the time hello was not a common greeting but was used simply to attract attention THE MOUTHPIECE is also the speaker A signal arriving from another phone makes the metal disk inside it vibrate producing a sound 1861 Telephon German Johann Reis transmits the phrase The horse does not eat cucumber salad with a device named the telephon A B 1876 First Telephone American Elisha Gray designs a telephone that uses a water-ﬁ lled microphone He patents it on the same day as Alexander Graham Bell’s telephone design 7

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