Thank Valdemar Poulsen for your music collection

In homes today people might possess recordings in a dozen different formats, from vinyl platters playable at various speeds, to tapes requiring half a dozen different machines to enjoy, to digital files stored on an array of devices.

They all, in one way or another, owe their existence to Danish engineer Valdemar Poulsen, who in 1898 first demonstrated the principle of magnetic recording, using a patented machine he called the telegraphone, which recorded and played back speech magnetically preserved on steel wire.

In 1900 he exhibited his invention at the Paris Exposition, making a recording of Austrian emperor Francis Joseph, which is believed to be the earliest surviving magnetic recording.

Poulsen was born on 23 November 1869 in Copenhagen. His father, a judge who served on the Danish High Court, wanted his son to become a doctor, and he did attend medical school for a short time, but at 24 he went to work as a technician for the Copenhagen Telephone Company. 

Some sources suggest Poulsen’s telegraphone was derived by work done by American inventor Oberlin Smith.

The online Museum of Magnetic Sound Recording cites an article published by Smith on 8 September titled “Some Possible Forms of the Phonograph”, in the British journal Electrical World, “where he suggested (probably for the first time) the use of permanent magnetic impressions for the recording of sound”.

“Smith suggested using cotton or silk thread, into which steel dust or short clippings of fine wire could be suspended. These particles were to be magnetised in accordance with the alternating current from a microphone source. Smith also discussed the possibility of using a hard steel wire but thought it scarcely possible. A working unit was never built.

“Many of Smith’s ideas were used by Valdemar Poulsen when he developed the first true magnetic recorder,” it says.

An article on wire recording published in the US Pacific northwest in 1998 by the University of Washington’s School of Music describes Poulsen’s telegraphone as being “strung-out piano wire and a primitive electromagnet connected to a microphone”.

“By passing the electromagnet over the wire as he spoke into the microphone, Poulsen created the first wire recording. All magnetic recordings (whether wire, tape, or disc) follow the same principle. As magnetic material is drawn past the recording head, it becomes and remains magnetised.

Poulsen’s early experiments used steel piano wire stretched between two walls at a slight angle so an electromagnet could slide down the wire at a uniform speed. Later versions used wire coiled between wooden spools, which could hold up to 30 minutes of recordings.

In 1903 Poulsen sought to market his invention in the US, founding the American Telegraphone Company.

The telegraphone was promoted as a tool for office dictation and a telephone answering machine, but it failed to take off, owing to drawbacks such as poor sound quality via headphones, and its unwieldy size. But the principles of magnetic recording Poulsen established were sound and showed the way ahead for later inventors.

Poulsen, meanwhile, had turned his attention to wireless radio and telegraph communication.

In an article published in the 2 April 1910 edition of the Journal of Electricity, Power and Gas, entitled “The Poulsen system of wireless telephony and telegraphy”, CF Elwell describes how “as soon as the methods of signalling through space first given to the world by Marconi were well understood, scientists throughout the world recognised the shortcomings of both the transmitting and receiving apparatus”.

Elwell describes the “many improvements” made in transmitting circuits, including those developed by Poulsen. He says Poulsen built a generator with which “the problem of telephoning through space was immediately solved”.

“Applied to telegraphy, it gives improved selectivity of the instruments to an extent never reached by spark methods, permits of duplex working, gives great range with small amounts of power, better results over land, better daylight working and, last but not least, a great increase in speed.”

The US Navy adopted Poulsen’s generator as standard equipment in 1912, but as with his wire recorder, others used his work as springboards to move far beyond his invention. By the 1920s Poulsen’s generator had been rendered obsolete by vacuum tubes.

He died on 23 July 1942 in Gentofte, Denmark.