Fax machine

The invention: Originally known as the “facsimile machine,” a
machine that converts written and printed images into electrical
signals that can be sent via telephone, computer, or radio.
The person behind the invention:
Alexander Bain (1818-1903), a Scottish inventor
Sending Images
The invention of the telegraph and telephone during the latter
half of the nineteenth century gave people the ability to send information
quickly over long distances.With the invention of radio and
television technologies, voices and moving pictures could be seen
around the world as well. Oddly, however, the facsimile process—
which involves the transmission of pictures, documents, or other
physical data over distance—predates all these modern devices,
since a simple facsimile apparatus (usually called a fax machine)
was patented in 1843 by Alexander Bain. This early device used a
pendulum to synchronize the transmitting and receiving units; it
did not convert the image into an electrical format, however, and it
was quite crude and impractical. Nevertheless, it reflected the desire
to send images over long distances, which remained a technological
goal for more than a century.
Facsimile machines developed in the period around 1930 enabled
news services to provide newspapers around the world with
pictures for publication. It was not until the 1970’s, however, that
technological advances made small fax machines available for everyday
office use.
Scanning Images
Both the fax machines of the 1930’s and those of today operate on
the basis of the same principle: scanning. In early machines, an image
(a document or a picture) was attached to a roller, placed in the
fax machine, and rotated at a slow and fixed speed (which must be the same at each end of the link) in a bright light. Light from the image
was reflected from the document in varying degrees, since dark
areas reflect less light than lighter areas do. Alens moved across the
page one line at a time, concentrating and directing the reflected
light to a photoelectric tube. This tube would respond to the change
in light level by varying its electric output, thus converting the image
into an output signal whose intensity varied with the changing
light and dark spots of the image. Much like the signal from a microphone
or television camera, this modulated (varying) wave could
then be broadcast by radio or sent over telephone lines to a receiver
that performed a reverse function. At the receiving end, a light bulb
was made to vary its intensity to match the varying intensity of the
incoming signal. The output of the light bulb was concentrated
through a lens onto photographically sensitive paper, thus re-creating
the original image as the paper was rotated.
Early fax machines were bulky and often difficult to operate.
Advances in semiconductor and computer technology in the 1970’s,
however, made the goal of creating an easy-to-use and inexpensive
fax machine realistic. Instead of a photoelectric tube that consumes
a relatively large amount of electrical power, a row of small photodiode
semiconductors is used to measure light intensity. Instead of a
power-consuming light source, low-power light-emitting diodes
(LEDs) are used. Some 1,728 light-sensitive diodes are placed in a
row, and the image to be scanned is passed over them one line at a
time. Each diode registers either a dark or a light portion of the image.
As each diode is checked in sequence, it produces a signal for
one picture element, also known as a “pixel” or “pel.” Because
many diodes are used, there is no need for a focusing lens; the diode
bar is as wide as the page being scanned, and each pixel represents a
portion of a line on that page.
Since most fax transmissions take place over public telephone
system lines, the signal from the photodiodes is transmitted by
means of a built-in computer modem in much the same format that
computers use to transmit data over telephone lines. The receiving
fax uses its modem to convert the audible signal into a sequence that
varies in intensity in proportion to the original signal. This varying
signal is then sent in proper sequence to a row of 1,728 small wires
over which a chemically treated paper is passed. As each wire receives a signal that represents a black portion of the scanned image,
the wire heats and, in contact with the paper, produces a black dot
that corresponds to the transmitted pixel. As the page is passed over
these wires one line at a time, the original image is re-created.
Consequences
The fax machine has long been in use in many commercial and
scientific fields.Weather data in the form of pictures are transmitted
from orbiting satellites to ground stations; newspapers receive photographs
from international news sources via fax; and, using a very
expensive but very high-quality fax device, newspapers and magazines
are able to transmit full-size proof copies of each edition to
printers thousands of miles away so that a publication edited in one
country can reach newsstands around the world quickly.
With the technological advances that have been made in recent
years, however, fax transmission has become a part of everyday life,
particularly in business and research environments. The ability to
send quickly a copy of a letter, document, or report over thousands
of miles means that information can be shared in a matter of minutes
rather than in a matter of days. In fields such as advertising and
architecture, it is often necessary to send pictures or drawings to remote
sites. Indeed, the fax machine has played an important role in
providing information to distant observers of political unrest when
other sources of information (such as radio, television, and newspapers)
are shut down.
In fact, there has been a natural coupling of computers, modems,
and fax devices. Since modern faxes are sent as computer data over
phone lines, specialized and inexpensive modems (which allow
two computers to share data) have been developed that allow any
computer user to send and receive faxes without bulky machines.
For example, a document—including drawings, pictures, or graphics
of some kind—is created in a computer and transmitted directly
to another fax machine. That computer can also receive a fax transmission
and either display it on the computer’s screen or print it on
the local printer. Since fax technology is now within the reach of almost
anyone who is interested in using it, there is little doubt that it
will continue to grow in popularity.

ENIAC computer

The invention: The first general-purpose electronic digital computer.
The people behind the invention:
John Presper Eckert (1919-1995), an electrical engineer
John William Mauchly (1907-1980), a physicist, engineer, and
professor
John von Neumann (1903-1957), a Hungarian American
mathematician, physicist, and logician
Herman Heine Goldstine (1913- ), an army mathematician
Arthur Walter Burks (1915- ), a philosopher, engineer, and
professor
John Vincent Atanasoff (1903-1995), a mathematician and
physicist
A Technological Revolution
The Electronic Numerical Integrator and Calculator (ENIAC) was
the first general-purpose electronic digital computer. By demonstrating
the feasibility and value of electronic digital computation, it initiated
the computer revolution. The ENIAC was developed during
World War II (1939-1945) at the Moore School of Electrical Engineering
by a team headed by John William Mauchly and John Presper
Eckert, who were working on behalf of the U.S. Ordnance Ballistic
Research Laboratory (BRL) at the Aberdeen Proving Ground in
Maryland. Early in the war, the BRL’s need to generate ballistic firing
tables already far outstripped the combined abilities of the available
differential analyzers and teams of human computers.
In 1941, Mauchly had seen the special-purpose electronic computer
developed by John Vincent Atanasoff to solve sets of linear
equations. Atanasoff’s computer was severely limited in scope and
was never fully completed. The functioning prototype, however,
helped convince Mauchly of the feasibility of electronic digital computation
and so led to Mauchly’s formal proposal in April, 1943, to
develop the general-purpose ENIAC. The BRL, in desperate need of
computational help, agreed to fund the project, with Lieutenant Herman Heine Goldstine overseeing it for the U.S. Army.
This first substantial electronic computer was designed, built,
and debugged within two and one-half years. Even given the highly
talented team, it could be done only by taking as few design risks as
possible. The ENIAC ended up as an electronic version of prior
computers: Its functional organization was similar to that of the
differential analyzer, while it was programmed via a plugboard
(which was something like a telephone switchboard), much like the
earlier electromechanical calculators made by the International Business
Machines (IBM) Corporation. Another consequence was that
the internal representation of numbers was decimal rather than the
now-standard binary, since the familiar electromechanical computers
used decimal digits.
Although the ENIAC was completed only after the end of the
war, it was used primarily for military purposes. In fact, the first
production run on the system was a two-month calculation needed
for the design of the hydrogen bomb. John von Neumann, working
as a consultant to both the Los Alamos Scientific Laboratory and the
ENIAC project, arranged for the production run immediately prior
to ENIAC’s formal dedication in 1946.
A Very Fast Machine
The ENIAC was an impressive machine: It contained 18,000 vacuum
tubes, weighed 27 metric tons, and occupied a large room. The
final cost to the U.S. Army was about $486,000. For this price, the
army received a machine that computed up to a thousand times
faster than its electromechanical precursors; for example, addition
and subtraction required only 200 microseconds (200 millionths of a
second). At its dedication ceremony, the ENIAC was fast enough to
calculate a fired shell’s trajectory faster than the shell itself took to
reach its target.
The machine also was much more complex than any predecessor
and employed a risky new technology in vacuum tubes; this caused
much concern about its potential reliability. In response to this concern,
Eckert, the lead engineer, imposed strict safety factors on all
components, requiring the design to use components at a level well
below the manufacturers’ specified limits. The result was a machine that ran for as long as three days without a hardware malfunction.
Programming the ENIAC was effected by setting switches and
physically connecting accumulators, function tables (a kind of manually
set read-only memory), and control units. Connections were
made via cables running between plugboards. This was a laborious
and error-prone process, often requiring a one-day set time.
The team recognized this problem, and in early 1945, Eckert,
Mauchly, and Neumann worked on the design of a new machine.
Their basic idea was to treat both program and data in the same way,
and in particular to store them in the same high-speed memory; in
other words, they planned to produce a stored-program computer.
Neumann described and explained this design in his “First Draft of
a Report on the EDVAC” (EDVAC is an acronym for Electronic Discrete
Variable Automatic Computer). In his report, Neumann contributed
new design techniques and provided the first general, comprehensive
description of the stored-program architecture.
After the delivery of the ENIAC, Neumann suggested that it
could be wired up so that a set of instructions would be permanently
available and could be selected by entries in the function tables.
Engineers implemented the idea, providing sixty instructions
that could be invoked from the programs stored into the function tables.
Despite slowing down the computer’s calculations, this technique
was so superior to plugboard programming that it was used
exclusively thereafter. In this way, the ENIAC was converted into a
kind of primitive stored-program computer.
Impact
The ENIAC’s electronic speed and the stored-program design of
the EDVAC posed a serious engineering challenge: to produce a
computer memory that would be large, inexpensive, and fast.Without
such fast memories, the electronic control logic would spend
most of its time idling. Vacuum tubes themselves (used in the control)
were not an effective answer because of their large power requirements
and heat generation.
The EDVAC design draft proposed using mercury delay lines,
which had been used earlier in radars. These delay lines converted
an electronic signal into a slower acoustic signal in a mercury solution; for continuous storage, the signal picked up at the other end
was regenerated and sent back into the mercury. Maurice Vincent
Wilkes at the University of Cambridge was the first to complete
such a system, in May, 1949. One month earlier, Frederick Calland
Williams and Tom Kilburn at Manchester University had brought
their prototype computer into operation, which used cathode-ray
tubes (CRTs) for its main storage. Thus, England took an early lead
in developing computing systems, largely because of a more immediate
practical design approach.
In the meantime, Eckert and Mauchly formed the Electronic Control
Company (later the Eckert-Mauchly Computer Corporation).
They produced the Binary Automatic Computer (BINAC) in 1949
and the Universal Automatic Computer (UNIVAC) I in 1951; both
machines used mercury storage.
The memory problem that the ENIAC introduced was finally resolved
with the invention of the magnetic core in the early 1950’s.
Core memory was installed on the ENIAC and soon on all new machines.
The ENIAC continued in operation until October, 1955,
when parts of it were retired to the Smithsonian Institution. The
ENIAC proved the viability of digital electronics and led directly to
the development of stored-program computers. Its impact can be
seen in every modern digital computer.

Electronic synthesizer

The invention: Portable electronic device that both simulates the
sounds of acoustic instruments and creates entirely new sounds.
The person behind the invention:
Robert A. Moog (1934- ), an American physicist, engineer,
and inventor
From Harmonium to Synthesizer
The harmonium, or acoustic reed organ, is commonly viewed as
having evolved into the modern electronic synthesizer that can be
used to create many kinds of musical sounds, from the sounds of
single or combined acoustic musical instruments to entirely original
sounds. The first instrument to be called a synthesizer was patented
by the Frenchman J. A. Dereux in 1949. Dereux’s synthesizer, which
amplified the acoustic properties of harmoniums, led to the development
of the recording organ.
Next, several European and American inventors altered and
augmented the properties of such synthesizers. This stage of the
process was followed by the invention of electronic synthesizers,
which initially used electronically generated sounds to imitate
acoustic instruments. It was not long, however, before such synthesizers
were used to create sounds that could not be produced by any
other instrument. Among the early electronic synthesizers were
those made in Germany by Herbert Elmert and Robert Beyer in
1953, and the American Olsen-Belar synthesizers, which were developed
in 1954. Continual research produced better and better versions
of these large, complex electronic devices.
Portable synthesizers, which are often called “keyboards,” were
then developed for concert and home use. These instruments became
extremely popular, especially in rock music. In 1964, Robert A.
Moog, an electronics professor, created what are thought by many
to be the first portable synthesizers to be made available to the public.
Several other well-known portable synthesizers, such as ARP
and Buchla synthesizers, were also introduced at about the same time. Currently, many companies manufacture studio-quality synthesizers
of various types.
Synthesizer Components and Operation
Modern synthesizers make music electronically by building up
musical phrases via numerous electronic circuits and combining
those phrases to create musical compositions. In addition to duplicating
the sounds of many instruments, such synthesizers also enable
their users to create virtually any imaginable sound. Many
sounds have been created on synthesizers that could not have been
created in any other way.
Synthesizers use sound-processing and sound-control equipment
that controls “white noise” audio generators and oscillator circuits.
This equipment can be manipulated to produce a huge variety of
sound frequencies and frequency mixtures in the same way that a
beam of white light can be manipulated to produce a particular
color or mixture of colors.
Once the desired products of a synthesizer’s noise generator and
oscillators are produced, percussive sounds that contain all or many
audio frequencies are mixed with many chosen individual sounds
and altered by using various electronic processing components. The
better the quality of the synthesizer, the more processing components
it will possess. Among these components are sound amplifiers,
sound mixers, sound filters, reverberators, and sound combination
devices.
Sound amplifiers are voltage-controlled devices that change the
dynamic characteristics of any given sound made by a synthesizer.
Sound mixers make it possible to combine and blend two or more
manufactured sounds while controlling their relative volumes.
Sound filters affect the frequency content of sound mixtures by increasing
or decreasing the amplitude of the sound frequencies
within particular frequency ranges, which are called “bands.”
Sound filters can be either band-pass filters or band-reject filters.
They operate by increasing or decreasing the amplitudes of sound
frequencies within given ranges (such as treble or bass). Reverberators
(or “reverb” units) produce artificial echoes that can have significant
musical effects. There are also many other varieties of soundprocessing elements, among them sound-envelope generators,
spatial locators, and frequency shifters. Ultimately, the soundcombination
devices put together the results of the various groups
of audio generating and processing elements, shaping the sound
that has been created into its final form.Avariety of control elements are used to integrate the operation
of synthesizers. Most common is the keyboard, which provides the
name most often used for portable electronic synthesizers. Portable
synthesizer keyboards are most often pressure-sensitive devices
(meaning that the harder one presses the key, the louder the resulting
sound will be) that resemble the black-and-white keyboards of
more conventional musical instruments such as the piano and the
organ. These synthesizer keyboards produce two simultaneous outputs:
control voltages that govern the pitches of oscillators, and timing
pulses that sustain synthesizer responses for as long as a particular
key is depressed.
Unseen but present are the integrated voltage controls that control
overall signal generation and processing. In addition to voltage
controls and keyboards, synthesizers contain buttons and other
switches that can transpose their sound ranges and other qualities.
Using the appropriate buttons or switches makes it possible for a
single synthesizer to imitate different instruments—or groups of instruments—
at different times. Other synthesizer control elements
include sample-and-hold devices and random voltage sources that
make it possible to sustain particular musical effects and to add various
effects to the music that is being played, respectively.
Electronic synthesizers are complex and flexible instruments.
The various types and models of synthesizers make it possible to
produce many different kinds of music, and many musicians use a
variety of keyboards to give them great flexibility in performing
and recording.
Impact
The development and wide dissemination of studio and portable
synthesizers has led to their frequent use to combine the sound
properties of various musical instruments; a single musician can
thus produce, inexpensively and with a single instrument, sound
combinations that previously could have been produced only by a
large number of musicians playing various instruments. (Understandably,
many players of acoustic instruments have been upset by
this development, since it means that they are hired to play less often
than they were before synthesizers were developed.) Another consequence of synthesizer use has been the development of entirely
original varieties of sound, although this area has been less
thoroughly explored, for commercial reasons. The development of
synthesizers has also led to the design of other new electronic music-
making techniques and to the development of new electronic
musical instruments.
Opinions about synthesizers vary from person to person—and,
in the case of certain illustrious musicians, from time to time. One
well-known musician initially proposed that electronic synthesizers
would replace many or all conventional instruments, particularly
pianos. Two decades later, though, this same musician noted
that not even the best modern synthesizers could match the quality
of sound produced by pianos made by manufacturers such as
Steinway and Baldwin.

Electron microscope

The invention: 



A device for viewing extremely small objects that

uses electron beams and “electron lenses” instead of the light

rays and optical lenses used by ordinary microscopes.



The people behind the invention:



Ernst Ruska (1906-1988), a German engineer, researcher, and

inventor who shared the 1986 Nobel Prize in Physics

Hans Busch (1884-1973), a German physicist

Max Knoll (1897-1969), a German engineer and professor

Louis de Broglie (1892-1987), a French physicist who won the

1929 Nobel Prize in Physics











Reaching the Limit





The first electron microscope was constructed by Ernst Ruska

and Max Knoll in 1931. Scientists who look into the microscopic

world always demand microscopes of higher and higher resolution

(resolution is the ability of an optical instrument to distinguish

closely spaced objects). As early as 1834, George Airy, the eminent

British astronomer, theorized that there should be a natural limit to

the resolution of optical microscopes. In 1873, two Germans, Ernst

Abbe, cofounder of the Karl Zeiss Optical Works at Jena, and Hermann

von Helmholtz, the famous physicist and philosopher, independently

published papers on this issue. Both arrived at the same

conclusion as Airy: Light is limited by the size of its wavelength.

Specifically, light cannot resolve smaller than one-half the height of

its wavelength.

One solution to this limitation was to experiment with light, or

electromagnetic radiation, or shorter and shorter wavelengths.

At the beginning of the twentieth century, Joseph Edwin Barnard

experimented on microscopes using ultraviolet light. Such instruments,

however, only modestly improved the resolution. In

1912, German physicist Max von Laue considered using X rays.

At the time, however, it was hard to turn “X-ray microscopy” into

a physical reality. The wavelengths of X rays are exceedingly

short, but for the most part they are used to penetrate matter, not

to illuminate objects. It appeared that microscopes had reached

their limit.





Matter Waves



In a new microscopy, then, light—even electromagnetic radiation

in general—as the medium that traditionally carried image information,

had to be replaced by a new medium. In 1924, French

theoretical physicist Louis de Broglie advanced a startling hypothesis:

Matter on the scale of subatomic particles possesses wave

characteristics. De Broglie also concluded that the speed of lowmass

subatomic particles, such as electrons, is related to wavelength.

Specifically, higher speeds correspond to shorter wavelengths.

When Knoll and Ruska built the first electron microscope in 1931,

they had never heard about de Broglie’s “matter wave.” Ruska recollected

that when, in 1932, he and Knoll first learned about de

Broglie’s idea, he realized that those matter waves would have to be

many times shorter in wavelength than light waves.

The core component of the new instrument was the electron

beam, or “cathode ray,” as it was usually called then. The cathoderay

tube was invented in 1857 and was the source of a number of

discoveries, including X rays. In 1896, Olaf Kristian Birkeland, a

Norwegian scientist, after experimenting with the effect of parallel

magnetic fields on the electron beam of the cathode-ray tube, concluded

that cathode rays that are concentrated on a focal point by

means of a magnet are as effective as parallel light rays that are concentrated

by means of a lens.

From around 1910, German physicist Hans Busch was the leading

researcher in the field. In 1926, he published his theory on the

trajectories of electrons in magnetic fields. His conclusions confirmed

and expanded upon those of Birkeland. As a result, Busch

has been recognized as the founder of a new field later known

as “electron optics.” His theoretical study showed, among other

things, that the analogy between light and lenses on the one hand,

and electron beams and electromagnetic lenses, on the other hand,

was accurate.

Beginning in 1928, Ruska, as a graduate student at the Berlin Institute

of Technology, worked on refining Busch’s work. He found

that the energy of the electrons in the beam was not uniform. This

nonuniformity meant that the images of microscopic objects would

ultimately be fuzzy. Knoll and Ruska were able to work from the

recognition of this problem to the design and materialization of a

concentrated electron “writing spot” and to the actual construction

of the electron microscope. By April, 1931, they had established a

technological landmark with the “first constructional realization of

an electron microscope.”





Impact



The world’s first electron microscope, which took its first photographic

record on April 7, 1931, was rudimentary. Its two-stage total

magnification was only sixteen times larger than the sample. Since

Ruska and Knoll’s creation, however, progress in electron microscopy

has been spectacular. Such an achievement is one of the prominent

examples that illustrate the historically unprecedented pace of

science and technology in the twentieth century.

In 1935, for the first time, the electron microscope surpassed

the optical microscope in resolution. The problem of damaging

the specimen by the heating effects of the electron beam proved

to be more difficult to resolve. In 1937, a team at the University of

Toronto constructed the first generally usable electron microscope.

In 1942, a group headed by James Hillier at the Radio Corporation

of America produced commercial transmission electron

microscopes. In 1939 and 1940, research papers on electron microscopes

began to appear in Sweden, Canada, the United States,

and Japan; from 1944 to 1947, papers appeared in Switzerland,

France, the Soviet Union, The Netherlands, and England. Following

research work in laboratories, commercial transmission electron

microscopes using magnetic lenses with short focal lengths

also appeared in these countries.











Ernst Ruska





Ernst August Friedrich Ruska was born in 1906 in Heidelberg

to Professor Julius Ruska and his wife, Elisabeth. In 1925

he left home for the Technical College of Munich, moving two

years later to the Technical College of Berlin and gaining practical

training at nearby Siemens and Halsk Limited. During his

university days he became interested in vacuum tube technology

and worked at the Institute of High Voltage, participating

in the development of a high performance cathode ray oscilloscope.

His interests also lay with the theory and application of electron

optics. In 1929, as part of his graduate work, Ruska published

a proof of Hans Busch’s theory explaining possible lenslike

effects of a magnetic field on an electron stream, which led

to the invention of the polschuh lens. It formed the core of the

electron microscope that Ruska built with his mentor, Max

Kroll, in 1931.

Ruska completed his doctoral studies in 1934, but he had already

found work in industry, believing that further technical

development of electron microscopes was beyond the means of

university laboratories. He worked for Fernseh Limited from

1933 to 1937 and for Siemens from 1937 to 1955. Following

World War II he helped set up the Institute of Electron Optics

and worked in the Faculty of Medicine and Biology of the German

Academy of Sciences. He joined the Fritz Haber Institute

of the Max Planck Society in Berlin in 1949 and took over as director

of its Institute for Electron Microscopy in 1955, keeping

the position until he retired in 1974.

His life-long work with electron microscopy earned Ruska

half of the 1986 Nobel Prize in Physics. He died two years later.

To honor his memory, European manufacturers of electron microscopes

instituted the Ernst Ruska Prizes, one for researchers

of materials and optics and one for biomedical researchers.



See also: Cyclotron; Field ion microscope; Geiger counter; Massspectrograph;

Neutrino detector; Scanning tunneling microscope;Synchrocyclotron;

Electron microscope.





Further Reading

Electroencephalogram

The invention: A system of electrodes that measures brain wave
patterns in humans, making possible a new era of neurophysiology.
The people behind the invention:
Hans Berger (1873-1941), a German psychiatrist and research
scientist
Richard Caton (1842-1926), an English physiologist and surgeon
The Electrical Activity of the Brain
Hans Berger’s search for the human electroencephalograph (English
physiologist Richard Caton had described the electroencephalogram,
or “brain wave,” in rabbits and monkeys in 1875) was motivated
by his desire to find a physiological method that might be
applied successfully to the study of the long-standing problem of
the relationship between the mind and the brain. His scientific career,
therefore, was directed toward revealing the psychophysical
relationship in terms of principles that would be rooted firmly in the
natural sciences and would not have to rely upon vague philosophical
or mystical ideas.
During his early career, Berger attempted to study psychophysical
relationships by making plethysmographic measurements of
changes in the brain circulation of patients with skull defects. In
plethysmography, an instrument is used to indicate and record by
tracings the variations in size of an organ or part of the body. Later,
Berger investigated temperature changes occurring in the human
brain during mental activity and the action of psychoactive drugs.
He became disillusioned, however, by the lack of psychophysical
understanding generated by these investigations.
Next, Berger turned to the study of the electrical activity of the
brain, and in the 1920’s he set out to search for the human electroencephalogram.
He believed that the electroencephalogram would finally
provide him with a physiological method capable of furnishing
insight into mental functions and their disturbances.Berger made his first unsuccessful attempt at recording the electrical
activity of the brain in 1920, using the scalp of a bald medical
student. He then attempted to stimulate the cortex of patients with
skull defects by using a set of electrodes to apply an electrical current
to the skin covering the defect. The main purpose of these
stimulation experiments was to elicit subjective sensations. Berger
hoped that eliciting these sensations might give him some clue
about the nature of the relationship between the physiochemical
events produced by the electrical stimulus and the mental processes
revealed by the patients’ subjective experience. The availability
of many patients with skull defects—in whom the pulsating
surface of the brain was separated from the stimulating electrodes
by only a few millimeters of tissue—reactivated Berger’s interest
in recording the brain’s electrical activity.Small, Tremulous Movements
Berger used several different instruments in trying to detect
brain waves, but all of them used a similar method of recording.
Electrical oscillations deflected a mirror upon which a light beam
was projected. The deflections of the light beam were proportional
to the magnitude of the electrical signals. The movement of the spot
of the light beam was recorded on photographic paper moving at a
speed no greater than 3 centimeters per second.
In July, 1924, Berger observed small, tremulous movements of
the instrument while recording from the skin overlying a bone defect
in a seventeen-year-old patient. In his first paper on the electroencephalogram,
Berger described this case briefly as his first successful
recording of an electroencephalogram. At the time of these
early studies, Berger already had used the term “electroencephalogram”
in his diary. Yet for several years he had doubts about the origin
of the electrical signals he recorded. As late as 1928, he almost
abandoned his electrical recording studies.
The publication of Berger’s first paper on the human encephalogram
in 1929 had little impact on the scientific world. It was either
ignored or regarded with open disbelief. At this time, even
when Berger himself was not completely free of doubts about the
validity of his findings, he managed to continue his work. He published
additional contributions to the study of the electroencephalogram
in a series of fourteen papers. As his research progressed,
Berger became increasingly confident and convinced of the significance
of his discovery.
Impact
The long-range impact of Berger’s work is incontestable. When
Berger published his last paper on the human encephalogram in
1938, the new approach to the study of brain function that he inaugurated
in 1929 had gathered momentum in many centers, both in
Europe and in the United States. As a result of his pioneering work,
a new diagnostic method had been introduced into medicine. Physiology
had acquired a new investigative tool. Clinical neurophysiology
had been liberated from its dependence upon the functional anatomical approach, and electrophysiological exploration of complex
functions of the central nervous system had begun in earnest.
Berger’s work had finally received its well-deserved recognition.
Many of those who undertook the study of the electroencephalogram
were able to bring a far greater technical knowledge of
neurophysiology to bear upon the problems of the electrical activity
of the brain. Yet the community of neurological scientists has not
ceased to look with respect to the founder of electroencephalography,
who, despite overwhelming odds and isolation, opened a new
area of neurophysiology.

Electrocardiogram

The invention: Device for analyzing the electrical currents of the
human heart.
The people behind the invention:
Willem Einthoven (1860-1927), a Dutch physiologist and
winner of the 1924 Nobel Prize in Physiology or Medicine
Augustus D. Waller (1856-1922), a German physician and
researcher
Sir Thomas Lewis (1881-1945), an English physiologist
Horse Vibrations
In the late 1800’s, there was substantial research interest in the
electrical activity that took place in the human body. Researchers
studied many organs and systems in the body, including the nerves,
eyes, lungs, muscles, and heart. Because of a lack of available technology,
this research was tedious and frequently inaccurate. Therefore,
the development of the appropriate instrumentation was as
important as the research itself.
The initial work on the electrical activity of the heart (detected
from the surface of the body) was conducted by Augustus D.Waller
and published in 1887. Many credit him with the development of
the first electrocardiogram. Waller used a Lippmann’s capillary
electrometer (named for its inventor, the French physicist Gabriel-
Jonas Lippmann) to determine the electrical charges in the heart and
called his recording a “cardiograph.” The recording was made by
placing a series of small tubes on the surface of the body. The tubes
contained mercury and sulfuric acid. As an electrical current passed
through the tubes, the mercury would expand and contract. The resulting
images were projected onto photographic paper to produce
the first cardiograph. Yet Waller had only limited sucess with the
device and eventually abandoned it.
In the early 1890’s,Willem Einthoven, who became a good friend
of Waller, began using the same type of capillary tube to study the
electrical currents of the heart. Einthoven also had a difficult time working with the instrument. His laboratory was located in an old
wooden building near a cobblestone street. Teams of horses pulling
heavy wagons would pass by and cause his laboratory to vibrate.
This vibration affected the capillary tube, causing the cardiograph
to be unclear. In his frustration, Einthoven began to modify his laboratory.
He removed the floorboards and dug a hole some ten to fifteen
feet deep. He lined the walls with large rocks to stabilize his instrument.
When this failed to solve the problem, Einthoven, too,
abandoned the Lippmann’s capillary tube. Yet Einthoven did not
abandon the idea, and he began to experiment with other instruments.
Electrocardiographs over the Phone
In order to continue his research on the electrical currents of the
heart, Einthoven began to work with a new device, the d’Arsonval
galvanometer (named for its inventor, the French biophysicist
Arsène d’Arsonval). This instrument had a heavy coil of wire suspended
between the poles of a horseshoe magnet. Changes in electrical
activity would cause the coil to move; however, Einthoven
found that the coil was too heavy to record the small electrical
changes found in the heart. Therefore, he modified the instrument
by replacing the coil with a silver-coated quartz thread (string).
The movements could be recorded by transmitting the deflections
through a microscope and projecting them on photographic film.
Einthoven called the new instrument the “string galvanometer.”
In developing his string galvanomter, Einthoven was influenced
by the work of one of his teachers, Johannes Bosscha. In the 1850’s,
Bosscha had published a study describing the technical complexities
of measuring very small amounts of electricity. He proposed the
idea that a galvanometer modified with a needle hanging from a
silk thread would be more sensitive in measuring the tiny electric
currents of the heart.
By 1905, Einthoven had improved the string galvanometer to
the point that he could begin using it for clinical studies. In 1906,
he had his laboratory connected to the hospital in Leiden by a telephone
wire.With this arrangement, Einthoven was able to study in
his laboratory electrocardiograms derived from patients in the hospital, which was located a mile away. With this source of subjects,
Einthoven was able to use his galvanometer to study many
heart problems. As a result of these studies, Einthoven identified
the following heart problems: blocks in the electrical conduction
system of the heart; premature beats of the heart, including two
premature beats in a row; and enlargements of the various chambers
of the heart. He was also able to study how the heart behaved
during the administration of cardiac drugs.A major researcher who communicated with Einthoven about
the electrocardiogram was Sir Thomas Lewis, who is credited with
developing the electrocardiogram into a useful clinical tool. One of
Lewis’s important accomplishments was his identification of atrial
fibrillation, the overactive state of the upper chambers of the heart.
During World War I, Lewis was involved with studying soldiers’
hearts. He designed a series of graded exercises, which he used to
test the soldiers’ ability to perform work. From this study, Lewis
was able to use similar tests to diagnose heart disease and to screen
recruits who had heart problems.
Impact
As Einthoven published additional studies on the string galvanometer
in 1903, 1906, and 1908, greater interest in his instrument
was generated around the world. In 1910, the instrument, now
called the “electrocardiograph,” was installed in the United States.
It was the foundation of a new laboratory for the study of heart disease
at Johns Hopkins University.
As time passed, the use of the electrocardiogram—or “EKG,” as
it is familiarly known—increased substantially. The major advantage
of the EKG is that it can be used to diagnose problems in the
heart without incisions or the use of needles. It is relatively painless
for the patient; in comparison with other diagnostic techniques,
moreover, it is relatively inexpensive.
Recent developments in the use of the EKG have been in the area
of stress testing. Since many heart problems are more evident during
exercise, when the heart is working harder, EKGs are often
given to patients as they exercise, generally on a treadmill. The clinician
gradually increases the intensity of work the patient is doing
while monitoring the patient’s heart. The use of stress testing has
helped to make the EKG an even more valuable diagnostic tool.

Electric refrigerator

The invention: 



An electrically powered and hermetically sealed

food-storage appliance that replaced iceboxes, improved production,

and lowered food-storage costs.



The people behind the invention:



Marcel Audiffren, a French monk

Christian Steenstrup (1873-1955), an American engineer

Fred Wolf, an American engineer








Ice Preserves America’s Food



Before the development of refrigeration in the United States, a

relatively warm climate made it difficult to preserve food. Meat

spoiled within a day and milk could spoil within an hour after milking.

In early America, ice was stored below ground in icehouses that

had roofs at ground level. GeorgeWashington had a large icehouse

at his Mount Vernon estate. By 1876, America was consuming more

than 2 million tons of ice each year, which required 4,000 horses and

10,000 men to deliver.

Several related inventions were needed before mechanical refrigeration

was developed. James Watt invented the condenser, an important

refrigeration system component, in 1769. In 1805, Oliver Evans

presented the idea of continuous circulation of a refrigerant in a

closed cycle. In this closed cooling cycle, a liquid refrigerant evaporates

to a gas at low temperature, absorbing heat from its environment

and thereby producing “cold,” which is circulated around an

enclosed cabinet. To maintain this cooling cycle, the refrigerant gas

must be returned to liquid form through condensation by compression.

The first closed-cycle vapor-compression refrigerator, which

was patented by Jacob Perkins in 1834, used ether as a refrigerant.

Iceboxes were used in homes before refrigerators were developed.

Ice was cut from lakes and rivers in the northern United States

or produced by ice machines in the southern United States. An ice

machine using air was patented by John Gorrie at New Orleans in



1851. Ferdinand Carre introduced the first successful commercial

ice machine, which used ammonia as a refrigerant, in 1862, but it

was too large for home use and produced only a pound of ice per

hour. Ice machinery became very dependable after 1890 but was

plagued by low efficiency. Very warm summers in 1890 and 1891 cut

natural ice production dramatically and increased demand for mechanical

ice production. Ice consumption continued to increase after

1890; by 1914, 21 million tons of ice were used annually. The high

prices charged for ice and the extremely low efficiency of home iceboxes

gradually led the public to demand a substitute for ice refrigeration.





Refrigeration for the Home



Domestic refrigeration required a compact unit with a built-in

electric motor that did not require supervision or maintenance.

Marcel Audiffren, a French monk, conceived the idea of an electric

refrigerator for home use around 1910. The first electric refrigerator,

which was invented by Fred Wolf in 1913, was called the Domelre,

which stood for domestic electric refrigerator. This machine used

condensation equipment that was housed in the home’s basement.

In 1915, Alfred Mellowes built the first refrigerator to contain all of

its components; this machine was known as Guardian’s Frigerator.

General Motors acquired Guardian in 1918 and began to mass produce

refrigerators. Guardian was renamed Frigidaire in 1919. In

1918, the Kelvinator Company, run by Edmund Copeland, built the

first refrigerator with automatic controls, the most important of

which was the thermostatic switch. Despite these advances, by 1920

only a few thousand homes had refrigerators, which cost about

$1,000 each.

The General Electric Company (GE) purchased the rights to the

General Motors refrigerator, which was based on an improved

design submitted by one of its engineers, Christian Steenstrup.

Steenstrup’s innovative design included a motor and reciprocating

compressor that were hermetically sealed with the refrigerant.

This unit, known as the GE Monitor Top, was first produced in

1927. Apatent on this machine was filed for in 1926 and granted to

Steenstrup in 1930. Steenstrup became chief engineer of GE’s electric

refrigeration department and accumulated thirty-nine addi-

tional patents in refrigeration over the following years. By 1936, he

had more than one hundred patents to his credit in refrigeration and

other areas.

Further refinement of the refrigerator evolved with the development

of Freon, a nonexplosive, nontoxic, and noncorrosive refrigerant

discovered by Thomas Midgely, Jr., in 1928. Freon used lower

pressures than ammonia did, which meant that lighter materials

and lower temperatures could be used in refrigeration.

During the years following the introduction of the Monitor Top,

the cost of refrigerators dropped from $1,000 in 1918 to $400 in 1926,

and then to $170 in 1935. Sales of units increased from 200,000 in

1926 to 1.5 million in 1935.

Initially, refrigerators were sold separately from their cabinets,

which commonly were used wooden iceboxes. Frigidaire began

making its own cabinets in 1923, and by 1930, refrigerators that

combined machinery and cabinet were sold.

Throughout the 1930’s, refrigerators were well-insulated, hermetically

sealed steel units that used evaporator coils to cool the

food compartment. The refrigeration system was transferred from

on top of to below the food storage area, which made it possible to

raise the food storage area to a more convenient level. Special light

bulbs that produced radiation to kill taste- and odor-bearing bacteria

were used in refrigerators. Other developments included sliding

shelves, shelves in doors, rounded and styled cabinet corners, ice

cube trays, and even a built-in radio.

The freezing capacity of early refrigerators was inadequate. Only

a package or two of food could be kept cool at a time, ice cubes

melted, and only a minimal amount of food could be kept frozen.

The two-temperature refrigerator consisting of one compartment

providing normal cooling and a separate compartment for freezing

was developed by GE in 1939. Evaporator coils for cooling were

placed within the refrigerator walls, providing more cooling capacity

and more space for food storage. Frigidaire introduced a Cold

Wall compartment, while White-Westinghouse introduced a Colder

Cold system. After World War II, GE introduced the refrigeratorfreezer

combination.



Impact



Audiffren,Wolf, Steenstrup, and others combined the earlier inventions

of Watt, Perkins, and Carre with the development of electric

motors to produce the electric refrigerator. The development of

domestic electric refrigeration had a tremendous effect on the quality

of home life. Reliable, affordable refrigeration allowed consumers

a wider selection of food and increased flexibility in their daily

consumption. The domestic refrigerator with increased freezer capacity

spawned the growth of the frozen food industry.Without the

electric refrigerator, households would still depend on unreliable

supplies of ice.