1. • TV= Television

2. • Television (TV) is
a telecommunication medium for transmitting
and receiving moving images that can
be monochrome (black-and-white) or colored,
with or without accompanying sound.
"Television" may also refer specifically to
a television set, television programming,
ortelevision transmission.

3. • The etymology of the word has a mixed Latin
and Greek origin, meaning "far sight":
Greek tele, far, and Latin visio, sight
(fromvideo, vis- to see, or to view in the first
person).

4. • Commercially available since the late 1920s,
the television set has become commonplace
in homes, businesses and institutions,
particularly as a vehicle for advertising, a
source of entertainment, and news.

5. • Since the 1950s, television has been the main
medium for molding public opinion

6. • Since the 1970s the availability of video
cassettes, laserdiscs, DVDs and now Blu-ray
Discs, have resulted in the television set
frequently being used for viewing recorded as
well as broadcast material.

7. • In recent years Internet television has seen
the rise of television available via the Internet,
e.g. iPlayer and Hulu.

8. • The history of television records the work of
numerous engineers and inventors in several
countries over many decades.

9. • In its early stages of development, television
employed a combination of optical,
mechanical and electronic technologies to
capture, transmit and display a visual image.

10. • The late 1920s, however, those employing
only optical and electronic technologies were
being explored.

11. • All modern television systems relied on the
latter, although the knowledge gained from
the work on electromechanical systems was
crucial in the development of fully electronic
television.

12. • The fundamental principles of television were
initially developed using electromechanical
methods to scan, transmit and reproduce an
image.

13. • As electronic camera and display tubes were
perfected, electromechanical television gave
way to all-electronic broadcast television
systems in nearly all applications.

14. • ^ a b Diggs-Brown, Barbara (2011) Strategic Public Relations: Audience
Focused Practice p.48
• ^ Television Frequency Table, CSGNetwork.com., a Division of Computer
Support Group.
• ^ Study Finds Link Between Television Viewing And Attention Problems In
Childrenretrieved 19 July 2012
• ^ "Paul Nipkow". Bairdtelevision.com. Retrieved 2012-11-02.
• ^ "Paul Nipkow and John Baird: The Inventors of the Mechanical
Television". Juliantrubin.com. Retrieved 2012-11-02.
• ^ "History of the Cathode Ray Tube". About.com. Retrieved 4 October
2009.
• ^ "World Analogue Television Standards and Waveforms – section –
Timeline". Histrorical television data 2011. Retrieved 29 January 2011.
• ^ R. W. Burns, John Logie Baird: television pioneer, IET, 2000 ISBN 0-85296-
797-7 pp. 73, 88

15. Radio

16. • Radio is the transmission of signals through
free space by electromagnetic radiation of
a frequency significantly below that of visible
light, in the radio frequency range, from about
3 kHz to 300 GHz.These waves are called radio
waves. Electromagnetic radiation travels by
means of oscillating electromagnetic
fields that pass through the air and
thevacuum of space.

17. • Information, such as sound, is carried by
systematically changing (modulating) some
property of the radiated waves, such as
their amplitude, frequency, phase, or pulse
width. When radio waves strike an electrical
conductor, the oscillating fields induce
an alternating current in the conductor. The
information in the waves can be extracted and
transformed back into its original form.

18. • The etymology of "radio" or "radiotelegraphy"
reveals that it was called "wireless
telegraphy," which was shortened to
"wireless" in Britain.

19. • The prefix radio- in the sense of wireless
transmission, was first recorded in the
word radioconductor, a description provided
by the French physicist Édouard Branly in
1897. It is based on the verb to radiate (in
Latin "radius" means "spoke of a wheel, beam
of light, ray").

20. • he word "radio" also appears in a 1907 article
by Lee De Forest.

21. • It was adopted by the United States Navy in
1912, to distinguish radio from several other
"wireless" communication technologies in use
at the time, such as the photophone.

22. • The term became common by the time of the
first commercial broadcasts in the United
States in the 1920s. (The noun "broadcasting"
itself came from an agricultural term, meaning
"scattering seeds widely.")

23. • Each system contains a transmitter. This
consists of a source of electrical energy,
producing alternating current of a
desired frequency of oscillation.

24. • An antenna (or aerial) is an electrical device
which converts electric currents into radio
waves, and vice versa. It is usually used with
a radio transmitter or radio receiver.

25. • Early uses were maritime, for sending
telegraphic messages using Morse
code between ships and land.

26. • The earliest users included the Japanese Navy
scouting the Russian fleet during the Battle of
Tsushima in 1905.

27. • One of the most memorable uses of marine
telegraphy was during the sinking of
the RMS Titanic in 1912, including
communications between operators on the
sinking ship and nearby vessels, and
communications to shore stations listing the
survivors.

28. • AM radio uses amplitude modulation, in
which the amplitude of the transmitted signal
is made proportional to the sound amplitude
captured (transduced) by the microphone,
while the transmitted frequency remains
unchanged.

29. • A História da Rádio em Datas (1819-1997) (in
Portuguese) - notes on etymology
• L. de Forest, article in Electrical World 22 June 1270/1
(1907), early use of word "radio."
• http://web.mit.edu/varun_ag/www/bose.html - It
contains a proof that Sir Jagadish Chandra Bose
invented the Mercury Coherer which was later used by
Guglielmo Marconi and along with other patents.
• Cheney, Margaret (1981). Tesla - Man Out of Time.
New York: Simon & Schuster. ISBN 978-0-7432-1536-7.