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. Wikipedia A&E Network voted Johannes Gutenberg "Man of the 2 nd Millennium"

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.

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.

Now back to the 2 nd 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 series of Clicks and Clacks or short and long buzzes were transmitted to the receiver. A weak current from The sender activates a relay that connects a battery to the buzzer.

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?” / / /

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. Digital picture is a digital image – it is made up of many pixels.

Analog sound waves can be stored directly in their analog form by cutting grooves on vinyl.

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. Sound is a pressure wave that will cause a diaphram to vibrate in response to it.

Bell’s First Telephone- Liquid 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.

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.

The Telephone Receiver/speaker

MIC – microphone REC - receiver

Electromagnets used in Tape Players too A – Tape HowStuffWorks 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. 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.