People to People Communication Technology Education

Basic Systems Telecommunications Audio and Video recordings Printing Systems Photographic Systems Drafting Systems

Telecommunications Telecommunication system – Communication systems exchanging information over a distance. Two major types Individual systems Mass Systems

Individual Systems 1830’s – Telegraph – Samuel Morse Works by sending a series of dots and dashes through an electrical circuit. Operator uses a transmitter to send signal (By breaking and completing the circuit) Receiver uses a sounder which turns the electrical pulses into sound

Individual Systems 1876 – Telephone – Alexander Graham Bell Works by turning sound waves into electrical pulses then back to sound waves. Signal sent to central offices on wires then sent between central offices by microwaves, towers or satellites, or by glass fiber optic cables.

Individual Systems Very Similar to today’s cell phones. Cell phones are basically a low power radio transmitter which send signals directly to a relay tower. Towers send the signal to a Mobile Telephone Switching Office The office connects to normal land lines and now the call travels like a normal telephone call.

Mass Telecommunication Systems Radio and Television Very Similar – Both change sound and light waves into high frequency signals These systems first use microphones and cameras to change sound and light into electrical pulses Transmitters then change these pulses into high frequency waves. These signals are then projected/broadcasted over a large area via broadcast tower.

Mass Telecommunication Systems A receiving antenna then captures these waves and separates them from any other waves. Speakers and televisions then change the electrical pulses back into sound and light.

Mass Telecommunication Systems Today Television signals are also broadcast by satellite dish systems and over cables. This replaces local broadcast towers.

Mass Communication Systems Communication satellites are placed about 22,300 miles from earth and receive and uplink from one location on earth. From that height satellites can transmit (downlink) to over 40% of the earths surface. Ex. A message beamed from a satellite in Boston could be received in Germany.

Audio / Video Recording Systems Audio / Video Recording Systems are extensions of Radio and Television Only difference is that these systems record instead of broadcast

1 st Invention – 1877 Thomas Edison – Phonograph No longer need to listen live to speaker or broadcast Audio / Video can be now recorded in 3 ways

Grooved Discs Discs were created with wavy grooves that were followed by stylus or needle The vibrations created a small electric charge which is amplified to create sound waves.

Magnetic Tape Plastic ribbon is fed through a recording unit The recording unit produces a pattern of magnetic charges on the coating Player then reads the charges and converts them to sound and light

Digital Codes on Disc Sound and Video is recorded and digitized (numbered) Each sound frequency has a different number Numbers are recorded on discs in pits and flats Player then reads numbers with a laser and converts information back to video and audio.