The Second Information
Superhighway was…
Passing current in wires to transmit
information over long distances.
With the discovery that electrical currents
can induce magnetic fields, there was now
an way to transmit audio as electrical
signals over wires and to detect small
currents traveling in wires at a receiver.
The First superhighway was the
widespread release of information as a
result of the Printing Press in the 1400’s
Johannes Gutenberg’s movable-type printing press
promoted the spread of knowledge. Information did not
have to come from clerics and royalty.
A&E Network voted Johannes Gutenberg "Man of the 2nd Millennium"
Wikipedia
Impacts of the Printing Press
► Rise
in Protestant Reformation
► Availability of Greek and Roman classic
literature, leading to the Renaissance
► Decline in the use of Latin
► Greater dissemination of scientific
information
Printing Press & the Chinese Language
► Chinese
developed
Woodblock Printing in 200
AD and Movable Block
printing on 1000 AD
► Using block printing, each
page is a carved block of
wood
► Moveable Type, where
each character is printed
separately, was still difficult
since Chinese language has
5000 basic characters.
European languages offered distinct advantages
over Chinese, leading to wider dissemination of
written materials and greater range of materials.
http://en.wikipedia.org
26 characters vs. 1000’s
► True
mass printing
could only thrive in
a culture with a
less sophisticated
writing system.
► A language with
an alphabet of few
characters took
advantage of the
benefits of movable
type printing.
http://www.computersmiths.com/chineseinvention/movtype.htm
http://www.scottberkun.com/blog/2006/09/
Now back to the 2nd Information
Superhighway…
Using wires to transmit information
Samuel Morse develops a code
comprised of dots and dashes.
Morse is granted a patent in 1837 for his
electromagnetic telegraph. It was later
simplified and replaced by the key
transmitter.
A weak current from
The sender activates
a relay that connects
a battery to the
buzzer.
A series of Clicks and Clacks or short and
long buzzes were transmitted to the receiver.
Using $30,000 obtained from congress,
Morse builds a 40 mile telegraph line from
Washington DC to Baltimore.
In 1844, the first message is sent:
“What hath God wrought?”
.-- .... .- - / .... .- - .... / --. --- -.. / .-- .-. --- ..- --. .... http://morsecode.scphillips.com/jtranslator.html
Transmission of Voice
Thomas Edison’s Phonograph and Telephone
technologies is applied to telegraph technology to
create the transmission of voice and music over
long distances.
Without wires - This is radio.
Using wires - this is what we typically think of as
basic telephone technology.
The first transatlantic wireless phone call was in
1915.
Dots and Dashes are digital
Voice and Music are analog
► Digital
is coding a signal using a binary
format, e.g. 0’s and 1’s, dots and dashes, on
and off
► Analog is the process of converting a signal
into a wide range of continuous values.
Photographic picture is an
analog image.
www.bbc.co.uk
Digital picture is a
digital image – it is
made up of many
pixels.
http://photo.net/equipment/digital/basics
Analog sound
waves can be
stored directly in
their analog form
by cutting
grooves on vinyl.
http://www.optics.rochester.edu
http://jvsc.jst.go.jp
Alexander Graham Bell and the Telephone
►
►
►
►
Very interested in assisting the deaf. Both his mother
and wife were deaf.
Devised hearing aides
Taught in a school for the deaf
Used the concept of Electromagnetic Induction to convert
sound waves (pressure wave) into electrical signals in 1876
Wikipedia
Bell patents the ‘electro-magnetic’ transmission
of vocal sound by means of an electric current.
http://sln.fi.edu
Sound is a pressure wave that will cause a
diaphram to vibrate in response to it.
http://www.acmi.net.au
Bell’s First TelephoneLiquid Transmitter
The sound wave vibrates the diaphragm
that in turn moves a rod up and down.
This changes the resistance making the
current change in consort with the sound
wave.
An electrical current is produced that
matches the pattern of the sound wave.
http://www.juliantrubin.com
Electro-Magnetic Receiver
(a speaker)
A changing
current in the
coil induces a
changing
magnetic field
around the
coil. The
force between
the permanent
magnet and
the coil causes
the diaphram
to vibrate and
reproduce the
original sound
wave.
A Watershed Moment
March 10, 1876
"I then shouted into M [the mouthpiece]
the following sentence: 'Mr. Watson-come here--I want to see you.' To my
delight he came and declared that he had
heard and understood what I said."
Wikipedia
Bell and others had many
iterations of transmitters and
receivers using various
technologies.
http://www.ctol.org.uk
The Telephone Receiver/speaker
http://www.privateline.com
http://www.telephonecollecting.org
MIC – microphone
REC - receiver
Electromagnets used in
Tape Players too
The electromagnet consists
of an iron core wrapped
with wire, as shown in the
figure. During recording,
the audio signal is sent
through the coil of wire to
create a magnetic field in
the core.
A – Tape
HowStuffWorks
This flux is what magnetizes
the oxide on the tape.
During playback, the motion
of the tape pulls a varying
magnetic field across the
gap. This creates a varying
magnetic field in the core
and therefore a signal in the
coil.