A D V E N T U R E S in C Y B E R S O U N DValdemar Poulsen : 1869 - 1942
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Valdemar Poulsen, (b. Nov. 23, 1869, d. July 1942), Danish telephone engineer and inventor, best known for his Telegraphone, which he patented in 1898. It was the first practical apparatus for magnetic sound recording and reproduction. It recorded, on a wire, the varying magnetic fields produced by a sound. The magnetized wire could then be used to play back the sound. The Telegraphone received considerable attention when it was exhibited at the Exposition Universelle in Paris in 1900. The few words that the Austrian emperor Francis Joseph spoke into it at that exhibition are believed to be the earliest surviving magnetic recording. Robert Long Source: Grolliers Encyclopedia
December 1, 1898, Danish electrical engineer and inventor Valdemar Poulsen patents the first practical magnetic sound recorder, the Telegrafoon, using magnetised piano wire as the recording medium.
Valdemar Poulsen, (b. Nov. 23, 1869, Copenhagen, Den.--d. July 1942, Copenhagen), Danish engineer who in 1903 developed the first device for generating continuous radio waves, thus aiding the development of radio broadcasting. After his education Poulsen joined the Copenhagen Telephone Company as an assistant in the technical section. While working there, he invented the telegraphone, an electromagnetic phonograph capable of registering human speech by the alternating magnetization of a wire. He applied for a patent on this device, a forerunner of the modern magnetic sound recorder, in 1898; a working model created great interest at the Paris Exposition in 1900. Even with this encouragement, he could not find financial backers in Europe. In 1903, with American associates, he founded the American Telegraphone Company for the manufacture and sale of an improved version of his device. The telegraphone recorded continuously for 30 minutes on a length of steel piano-wire moving at a speed of 84 inches (213 cm) per second. The device did not have wide application, however. Also in 1903 Poulsen obtained an English patent on his adaptation of a "singing arc" for radio purposes. Invented by the Englishman William Duddell, the singing arc could generate continuous audio waves (hence its name). Poulsen transformed this device so that it could generate radio waves; the arc was formed between a copper cathode (positive terminal) and a carbon anode (negative terminal) in an atmosphere of a hydrocarbon gas and a transverse magnetic field. Subsequent efforts with this device by Poulsen and others made long-wave radio broadcasting possible by 1920.
Magnetic recording dates to 1898, when Danish engineer Valdemar Poulsen developed a method for recording sound on a steel wire. He stretched this wire across his laboratory and put the recording apparatus on a trolley that traveled along that wire. He would run along with the moving trolley, talking into its microphone to record sound on the wire. To play back this sound, he would roll a second trolley containing the playback equipment along the wire and it would reproduce the sound. Having proven the principle of magnetic recording, Poulsen and others began to develop wire recorders. In these devices, a wire rolling from one drum to another was used to record and play back sound. In 1927, American inventor J. A. O'Neill replaced the wire with a magnetically coated ribbon and since then magnetic tape recorders have dominated the recording industry.
In 1889 (1898?) the first magnetic recording is achieved by the Danish Physicist Valdemar Poulsen. His device, the Telegrafoon, was essentially a long piece of steel wire wound helically on a cylinder rotating under an electromagnet connected to a carbon microphone or an earphone. The elctromagnet moved along the cyliner on a set of small rails.
 Poulsen's 'Drum' Telegraphone (Telegrafoon), c.1898
In 1898 vond de Deense ingenieur Valdemar Poulsen een apparaat uit dat langs magnetische weg geluid kon opnemen en weergeven. Voor dit doel gebruikte hij een stalen draad of band met een laagje metaaloxide, waarop magnetische velden achter konden blijven. Hij noemde het apparaat een 'Telegrafoon' en demonstreerde het voor het eerst op de Wereldtentoonstelling van 1900 in Parijs. Voor Poulsen had Alexander Graham Bell (van de telefoon) wel al geexperimenteerd met magnetische geluidsregistratie. Hij gebruikte papier met een mengsel van inkt en ijzerdeeltjes. De resultaten waren niet al te goed en zo kwam het dat Poulsen hem te snel af was.
Valdemar Poulsen, Danish scientist, (b: November 23, 1869 d: August 6, 1942 Copenhagen, Denmark), the son of a judge in the highest court of Denmark, harnessed the electric arc to wireless to extend its range. After studying for a degree in natural sciences at the University of Copenhagen, 1889-93, he entered the technical department of the Copenhagen Telephone Company. The Telegraphon became his specialty. It was an ingenious apparatus for recording telephone conversations electromagnetically on a steel wire, for repetition at will.
 Poulsen's Telegraphone (or in Danish, Telegrafoon), 1898
 Poulsen's Telegraphone Patent of 1898
An article describing the working of the Telegraphone and similar systems
 Poulsen's American Telegraphone of 1915
After inventing the Telegraphone, Poulsen left the telephone company in order to be free to conduct a series of experiments and to follow a new line of investigation that had suggested itself to him. In 1900 his telephone research gained for him the Grand Prix of Paris. Three years later he initiated a new method of generating continuous electric waves by means of the arc. In 1904 he was transmitting the voice over appreciable distances.
 The Poulsen Arc Transmitter Image Source: Wedlake G.E.C., 'SOS: The Story of Radio Communication'
 The First Complete Arc Transmitter and receiver built by Poulsen Wireless in 1910 in Palo Alto
L to R: Doug Perham, F. Albertus, and Peter V. Jensen. Image Source: http://www.best.com/~perham/photos/508b.htm
In 1907 Poulsen received the Gold Medal of the Royal Danish Society for Science, and in 1909 the University of Leipzig conferred upon him the honorary degree, Doctor of Philosophy. He received from the Danish government the Medal of Merit, an honor he. shared at that time with Nansen, Georg Brandes, Sven Hedin and Amundsen. At his death Dr. Poulsen was a fellow of the Danish Academy of Sciences, the Danish Academy of Technical Science and the Swedish Institute for Engineering Research.
 1000 kw Poulsen Arc Converter installed at Lafayette Radio Station
Poulsen's arc as a generator of continuous waves differed from the usual arc since it burned in an atmosphere containing hydrogen in a strong transverse magnetic field. The Federal Telegraph Company, specializing in arc transmitters, brought Poulsen's arc to America. When NAA, the United States naval spark station at Arlington, Virginia, went into commission in 1912, an arc also was installed; thus two rivals, Fessenden with the spark 1, Poulsen with the arc met on a common proving ground. Arc transmitters up to 500 kilowatts were tested by the Navy. One main disadvantage was found in that the arc emitted harmonics and arc mush; the heat was so terrific that a water cooling system was required. Nevertheless, during the First World War a number of battleships carried arc transmitters.
 Federal Telegraph's engineering staff, 1917
L to R: Leonard Fuller, Chief Engineer; Harold Elliot, Chief Draftsman; Corwin Chapmen, Lab. Engineer;
The original Poulsen 100 W arc, brought from Denmark by Elwell, is in the forground. Image Source: http://www.best.com/~perham/photos/503.htm
Later the U.S.S. George Washington, which took President Wilson to the Peace Conference, was equipped with an arc in hopes that communication might be maintained all the way across the sea. It was a triumph for radio when the Washington entering the harbor at Brest flashed signals from its arc which were picked up at Otter Cliffs, Bar Harbor, Maine, and a 600-word message was received without the loss of a word. Then came the (F.W.) Alexanderson alternator, a more efficient generator of radio waves, and the arc transmitter, along with the spark, became a wonder of the past; The powerful electron tube was to do the same for the alternator.
The method of generating continuous electric waves by means of a light arc 2 was invented by the Danish engineer Valdemar Poulsen in 1902 as a modification of William Du Bois Duddell's 'singing arc' of 1900.
Poulsen Arc Transmitter [...] In the early days of wireless, messages were encoded in dots and dashes and sent by spark transmitters. Conveying voice or music by radio required a continuous-wave (CW) transmitter, and the first successful CW transmitter was the invention of the Danish engineer Valdemar Poulsen. Poulsen was already known for another invention, the Telegraphone, the world's first functional magnetic recorder, patented in 1899. Poulsen's invention of the arc transmitter built upon the work of the English engineer William Duddell, who had discovered how to make a resonant circuit using a carbon-arc lamp. Duddell's Musical Arc operated at audio frequencies, and Duddell himself concluded that it was impossible to make the arc oscillate at radio frequencies. In 1902, however, Poulsen succeeded in doing just that -- by modifying the electrodes, placing the arc in an atmosphere of hydrocarbon vapor or pure hydrogen, and adding a transverse magnetic field. Poulsen's transmitter was used worldwide in the second and third decades of the century until it was displaced by transmitters that employed the vacuum tube as a generator of continuous waves.[...]
The Poulsen System From: Wireless Telegraphy by W.H. Marchant (1914) The Poulsen system is based on the discovery of Mr Duddell that if a current arc is shunted by a circuit containing capacity and inductance there will be established in the circuit electrical oscillations, the frequency of which depends upon the value of the inductance and capacity. The reason for this is that unlike a metallic conductor the arc does not follow Ohm's law and the curve showing the relation between current and terminal voltage is not a straight rising line, but has what is termed a falling characteristic, that is to say, if the current through the arc be increased the potential difference at its terminals will drop. Suppose now that a circuit with capacity and inductance in series is placed across the terminals of an arc, the condenser will charge, and in doing so, the current through the arc lessened, the potential difference at its terminals will increase and the condenser to a still higher voltage. After the capacity is fully charged the current through the arc will increase, and owing to the drop in voltage which it causes the condenser will discharge across the arc, and the discharge will, if the resistance is small, be oscillatory. In order to obtain oscillations of considerable energy Mr Duddell found that it was necessary to use a capacity of the order of I microfarad, and with a capacity of this magnitude it was not possible to obtain the very high frequencies needed for Radio-Telegraphy. Poulsen's great discovery was the effect of a hydrogen atmosphere which by cooling the arc increased the steepness of its characteristic curve, and also the use of very powerful magnetic field which enabled him to get a high terminal voltage. By the use of the arc burning in a hydrogen atmosphere, and the powerful transverse magnetic field, he was able to use a small capacity and thus get oscillations of the frequencies useful for Radio-Telegraphy and at the same time powerful. The practical construction of the Poulsen arc is as follows: the anode is made of copper and the end takes the form of a beak. The cathode is of carbon about one inch in diameter, the arc striking between the copper beak and the edge of the carbon. The carbon is fitted in a holder which is slowly rotated by means of a small motor, and as it burns away a fresh surface is presented and the length of the arc kept constant. The arc-length is also adjustable by means of a screw fitted to the copper electrode. The electrodes are taken through insulating sleeves in the sides of a water-cooled metallic chamber which is also flanged on the outside to assist the cooling. Through the sides of the chamber, and transversely to the electrodes, pass the pole pieces of a powerful electro-magnet which blows the arc out into a loop, the winding of the magnets being in series with the arc also serve as a choking coils and prevent the oscillations from passing back into the supply circuit. The chamber in which the arc burns is supplied with hydrogen through a tube let into its base and after passing through the chamber escapes through an outlet at the top and is conveyed away by means of a tube connected to it. The arc is connected across a 500 volt direct-current supply an across it is shunted the primary circuit, which consists of a condenser and an inductance in series. The antennae is connected to one point of the inductance and the earth wire to another. Signalling is effected by shorting through the Morse key a turn or two of the inductance which alters the wave-length and throws the transmitter in and out of tune with a receiver, a difference of about 5 per cent, being sufficient. As energy is supplied to the antennae at every swing the oscillations emitted from the Poulsen generator are continuous and undamped, or practically so. The Poulsen transmitter is unlike that of any other system inasmuch as no detector is made use of, but the received energy accumulated in a condenser and discharged at intervals through the telephone by means of a piece of apparatus which the inventor has named a tikker. A primary coil with variable condenser across its terminals to adjust the turning is coupled to the secondary circuit, which also consists of a coil and a variable condenser; across the terminals of this condenser is joined a mica condenser of fairly large capacity and the tikker, which is an intermittent contact formed by two gold-plated brass wires crossing each other at right angles, one of them being mounted at the end of a small electro-magnetic make and break similar in construction to a trembler bell. The telephone, which is of low resistance, is joined across the mica condenser. The action of the tuner is as follows: -the primary having been tuned to the sending-station and the secondary tuned to the primary; during the intervals when the tikker contacts are open the secondary circuit is left free resonate up, and the energy of many oscillations thus accumulated when the tikker contacts close, the circuit, owing to the added capacity of the mica condenser, which is now in parallel, will oscillate to a lower frequency. The opening of the tikker contacts will be determined by the presence or absence of a current across them, as this determines the conductivity of the small gap between the wires as the tikker starts to open. It will thus be seen that when the current is passing through zero the mica condenser, charged as it is with the greater part of the energy, will be disconnected from the secondary circuit and discharge through the telephone. The coupling between the primary and the secondary is very loose and full use is thus made of resonance, the tuning being so sharp that a difference of 4 or 5 per cent. In the wave-length is sufficient to render the signals inaudible. The tikker method, although one of the most sensitive means known for detecting electrical oscillations, labours under the disadvantage that it is not able to receive signals from the ordinary spark transmitters which give out damped and discontinuous oscillations. Related Sites http://shell3.ba.best.com/~sfmuseum/hist/poulsen.html#TOP http://www.aau.dk/~stenomus/person/hb.ukref.htm
Associated Text(s) M. Clark and Henry Nielsen, Crossed Wires and Missing Connections: Valdemar Poulsen, The American Telegraphone Company, and the Failure to Commercialize Magnetic Recording Business History Review 69 (1995) pp. 1-41.
Correspondence 1 From Donald Kimberlin Subject: Valdemar Poulsen Donald Kimberlin believes that this should more correctly be "...Fessenden with the alternator...." he writes...
"If you read Fessenden's history, you find out that he originally was an associate of Edison, and was familiar with rotating generators. Then, at least as early as 1899, Fessenden wanted a high-frequency alternator for the purpose of transmitting speech by radio. According to Fessenden's history, it took three tries by G.E.'s Alexanderson to produce a successful one, which Fessenden finally used in 1906 at Brant Rock, Massachusetts, to make what radio broadcasting historians rather universally regard as the first "program" of talk, music and such by radio on December 24, 1906."and from a further mailing...
"...At any rate, thanks for setting Fessenden's place straight. He really is a hero of the alternator, which arises from his own electrical power engineering naissance with Edison. It's just nice to see him on his proper pedestal in the pantheon of telecommunications gods." 2 From David L. Quinlan Subject: Valdemar Poulsen
"In your Poulsen article the term "light arc" should read "arc lamp" ...however, here is a story related to Poulsen which I read in a radio magazine when I was in school.(1950's). Back to the Top | Scientists and Engineers N - Z | Quit | eMail: Dr Russell Naughton |
