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Edison, Thomas Alva

Thomas Alva Edison was one of the most prolific inventors of the late 19th century.

He is most famous
for his development of the first commercially practical incandescent lamp (1879).

Perhaps his greatest contribution,
however,
was the development (1882) of the world's first central electric light-power station (see POWER,
GENERATION AND TRANSMISSION OF).

His early laboratories were forerunners of the modern industrial research laboratory,
where skilled researchers jointly solve technological probleMs.
Edison was born in the village of Milan,
Ohio,
on Feb.

11,
1847,
and his family later moved
to Port Huron,
Mich.

His formal schooling was limited
to three months,
at the age of seven,
but thereafter his mother tutored him,
and he was an avid reader.

At age 12 he became a train-boy,
selling magazines and candy on the Grand Trunk Railroad.

He spent all he earned on books and apparatus
for his chemical laboratory.

An accident at about this time eventually led
to a loss of hearing.


A station agent taught him telegraph code and procedures,
and at age 15 Edison became manager of a telegraph office.

His first inventions were the transmitter and receiver
for the automatic telegraph.

At 21,
Edison produced his first major invention,
a stock ticker
for printing stock-exchange quotations in brokers' offices.


with the $40,000 he was paid
for improvements in tickers,
he established a manufacturing shop and a small laboratory in Newark,
N.J.

Deciding
to give up manufacturing,
he moved the laboratory
to Menlo Park,
N.J.,
where he directed groups of employees working on various projects.

The original Menlo Park facility is now at the Henry Ford Museum in Dearborn,
Mich.


In 1878,
Edison began work on an electric lamp and sought a material that could be electrically heated
to incandescence in a vacuum.

At first he used platinum wire in glass bulbs at 10 volts.

He connected these bulbs in series
to utilize a higher supply voltage;
however,
he realized that independent lamp control would be necessary
for home and office use.

He then developed a three-wire system
with a supply of 220 volts.

Each lamp operated at 110 volts,
and the higher voltage required a resistance greater than that of platinum.

Edison conducted an extensive search
for a filament material
to replace platinum until,
on Oct.

21,
1879,
he demonstrated a lamp containing a carbonized cotton thread that glowed
for 40 hours.


Edison installed the first large central power station on Pearl Street in New York City in 1882;
its steam-driven generators of 900 horsepower provided enough power
for 7,200 lamps.

The success of this station led
to the construction of many other central stations.

Edison founded The Edison Electric Light Company (1878),
which eventually merged
with other companies in
to the General Electric Company (1892),
one of the largest U.S.

manufacturers.

He consistently opposed,
however,
switching the power stations from DIRECT CURRENT
to ALTERNATING CURRENT a change that would have increased transmission voltages considerably.


During his experiments on the incandescent bulb,
Edison noted a flow of electricity from a hot filament across a vacuum
to a metal wire.

This phenomenon,
known as THERMIONIC EMISSION,
or the Edison effect,
was the foundation of electronic inventions of the 20th century.


Edison also invented (1877) the PHONOGRAPH,
the invention he was most proud of;
it used tinfoil and wax cylinders
to record the sound.

His introduction of flexible celluloid film and his invention of the movie projector aided the development of motion pictures (see FILM,
HISTORY OF).

His other inventions include the alkaline storage battery,
a magnetic process
to separate iron ore,
and the carbon microphone.

After World War I he became interested in domestic sources of rubber and investigated various plant species
for rubber content.

By the time he died at West Orange,
N.J.,
on Oct.

18,
1931,
he had patented over 1,000 inventions.incandescent lamp
{in-kan-des'-ent}
The incandescent LAMP is a device
for producing light by passing an electric current through a metallic filament,
thereby heating the filament
to a high temperature.

The filament is placed inside an evacuated bulb,
which is attached
to the lamp base.


Although light is desired in the visible spectrum,
quantities of infrared and some ultraviolet are also produced,
decreasing the luminous efficiency.

The efficiency,
in lumens per watt,
may be increased by raising the temperature of the filament,
since more of the output energy is transferred from the infrared
to the visible spectrum.

The first lamps,
produced in 1880 by Thomas EDISON,
used carbonized strips of bamboo
for the filament;
since carbon has a high melting point--3,598 deg C (6,510 deg F)--it evaporates or sublimates from the solid phase much below this temperature,
and early carbon lamps had
to be operated at a lower temperature
to prolong their life.

Osmium,

with a melting point at 2,700 deg C (4,890 deg F),
and tantalum,

with a melting point at 2,900 deg C (5,250 deg F),
were later used
for filaments,
but ductile tungsten superseded these metals when it became available in 1912.

Since tungsten melts only at 3,382 deg C (6,120 deg F),
it operates at a higher temperature and emits a much whiter light.


Tungsten
for filaments is formed in
to coils
to concentrate the radiating surface.

The luminous efficiency is about 22 lumens per watt,
although short-life photoflood lamps reach 35.8 lumens per watt.

Vaporization of tungsten causes blackening of the bulb,
and inert gas is usually added
to reduce this evaporation.

A variety of bulb shapes is used,

with clear,
colored,
or frosted glass
to reduce glare.

Reflective material and lenses can be added
for beam control.phonograph
The term phonograph was coined by inventor Thomas EDISON
for his cylinder sound-recording apparatus.

In the United States the term became synonymous
with record player and was used
for all record-playing equipment.

Emile Berliner,
who invented the first commercially practical disk recording system,
used the term gramophone (originally Gram-O-Phone)
for it,
and that term was adopted in most of the world
to distinguish the disk system from the cylinder phonograph system.


ORIGINS
There were a number of precursors
to the invention of the phonograph.

Leon Scott de Martinville in 1857 invented the phonautograph,
a device that made permanent visual records of sound vibrations.

Only a few months before Edison produced his first sketches,
Charles Cros designed a similar device in France,
but no working model was built at the time.


Unequivocally,
the credit
for the first documented device that would both record and reproduce sound goes
to Thomas Edison.

The basic concepts occurred
to him during the summer of 1877,
when he was at work on telegraph repeating equipment.

He realized that an embossed disk,
tape,
or cylinder could be used
to record acoustic vibrations in permanent form and
to activate a playback system that,
in moving over the embossed surface,
would create an acoustic facsimile of the original sound.

He even suggested electromechanical devices that predated much later developments.

When he sketched a device
for his machinist,
John Kruesi,

to build as a working model,
probably in November of that year,
it was in the form of a hand-turned,
grooved metal cylinder,
oriented
with its axis horizontal.

A sheet of tinfoil was stretched over the cylinder.

Sound pressure against a diaphragm pressed a stylus in
to the surface of the tinfoil,
embossing it;
in playback,
the tinfoil in turn pushed against the stylus,
which moved the diaphragm
to produce sound.

The model,
finished in December,
was successful and was the first operating sound-recording apparatus.

A patent was issued on Feb.

19,
1878.


At the Volta Laboratory in Washington,
D.C.,
Chichester Bell and Charles Tainter developed several variants of Edison's phonograph.

The most important,
substituting a wax-covered cardboard cylinder
for the tinfoil,
was patented in 1885.

This patent,
which specified that the groove was engraved (implying the removal of some wax,
rather than its mere indentation as in the embossing of Edison's tinfoil),
was later used by those who then controlled it
to outflank Edison,
even though his notes (if not his original U.S.

patent) appear
to have allowed
for engraving as well as embossing.

The engraved-wax process had,
by then,
proved crucial
to the mass production of molded cylinder recordings.


The disks Emile Berliner made in 1888,
by contrast,
used an etching process.

The master disk was of zinc,
covered by an acid-proof resist.

In recording,
this resist was scratched by the stylus
to expose the zinc.

The master was then immersed in acid,
which removed the exposed zinc
to create the groove.

A mold,
or stamper,
made from the master was then used
to form hard-rubber (later,
shellac) disks.


The contours of the etched groove,
however,
were irregular,
producing much noisier sound than the wax process.

By 1901,
Berliner was using a modified wax process
for his disks.

The improved technical quality,
the appearance shortly thereafter of 10-inch and then 12-inch disks (
with their longer recording times by comparison
to the 7-inch zinc master disks),
and the growing number of musical stars who were persuaded
to make records by Berliner's process in the early 20th century all helped
to make it a commercial success.


In Edison's arrangement the groove had been impressed vertically in
to the recording surface,

with the stylus (in either recording or playback) riding up and down in response to--or in re-creation of--the sound wave (vertical modulation);
Berliner's stylus had
to move from side
to side across the surface of the disk (lateral modulation).

By 1920 most companies were using Berliner's lateral cut exclusively.


By 1926 the acoustic process--in which sound pressure alone created the groove modulation,
and groove modulation alone created the sound waves in playback--had been superseded by the electrical process,
in which electrical signals acted as an intermediary between the essentially mechanical properties of sound and of the record groove;
electromechanical transducers such as microphones,
cutters,
phonograph pickups,
and loudspeakers were used
to make the conversion from one form of energy
to the other.

By this date all the major record brands were recording electrically.


LATER DEVELOPMENTS
The next major technological change took place in 1948 in the United States,
when Columbia Records introduced the long-playing record (LP),
which was recorded and played back at a speed of 33 and 1/3 revolutions per minute (rpm),
and had fine,
closely spaced grooves called microgrooves.

Earlier,
similar long-playing records had
to be recorded continuously if they were
to play continuously;
any mistakes in the recording would require a whole new "take" lasting 20 minutes or so.

Columbia solved this problem by first tape-recording the program.

Short musical numbers or passages could then be edited together
to assemble a master lasting up
to about 30 minutes,
and mistakes could be corrected without redoing the entire program.


Soon thereafter,
RCA Victor introduced a smaller 45-rpm disk that also used the microgroove;
eventually the 45 became the medium
for popular "single" recordings.

By this time STEREOPHONIC SOUND had also become available,
the basic processes involved already having been investigated by the British engineer A.

D.

Blumlein in the 1930s.

In 1958 the recording industry adopted a variant in which,
in effect,
one groove wall held the left-channel signal and the other the right-channel signal.


The late 1970s saw the development of pulse-code modulation (PCM),
a recording technique that reduces the noise and distortion that had been unavoidable in earlier recording methods.

In the recording process,
PCM analyzes sound and stores it as a series of digital pulses.

These pulses are reconverted in
to acoustic signals
to produce conventional records.

The COMPACT DISC (CD),
an innovation that first appeared in the early 1980s,
uses a new technology that inscribes PCM information--that remains in digital form--directly on a disc
with a laser beam instead of the groove-cutting stylus of earlier recording.

The CD,
however,
requires its own player.


BASIC OPERATION

to play a stereo record,
the disk is placed on a TURNTABLE that rotates at a constant speed.

A tone arm carrying a stereo CARTRIDGE is mounted next
to the turntable.

The arm usually pivots
to rest its stylus lightly on the record groove and
to track the two sound channels inscribed in the groove walls.

(Less common is linear tracking,
in which the tone arm is mounted on a track.

Driven by a separate motor,
the entire arm moves in the track as the stylus follows the grooves,
and--unlike the pivoted tone arm--maintains the same optimal position in relation
to the grooves over the entire surface of the record.) The stylus vibrates in response
to the variations in the grooves,
and the vibration is converted in
to an electrical signal,
which,
when strengthened by an AMPLIFIER,
drives the LOUDSPEAKERS.

There the signal is converted back in
to acoustic vibrations.


Instead of a tone arm,
the compact disc player uses a laser beam and a photoelectric cell
to read the sound pattern imprinted on the disc as a series of microscopic pits.

This digital version of the original acoustic signal is translated back in
to acoustic vibrations within the loudspeakers.