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

1st 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.