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Famous Danish inventions

The Danish Patent and Trademark Office has compiled this unofficial list of key Danish inventions.

Magnetic Storage

Piano wire, an electromagnet and a microphone. This was all the Danish inventor Valdemar Poulsen (1869-1942) needed in 1898 to create the telegraphone or wire recorder – the first known device capable of recording sound magnetically. It was the direct forerunner of the tape recorder and the hard disk, and for his invention Poulsen was awarded the Grand Prix at the International Exhibition in Paris in 1900.

The Loudspeaker

On Christmas Eve 1915, an expectant crowd of 75,000 people stood in front of the City Hall in San Francisco to watch the Danish inventor Peter L. Jensen (1886-1962) demonstrate the world's first loudspeaker. Cheers erupted as the singing voice of a well-known opera diva of the day filled the airwaves, and resonated over a distance of 1½ kilometres. In the USA, Peter L. Jensen was regarded as the Danish Edison, and one of the most expensive loudspeaker brands is still called Jensen. He later said that he came to regret his invention when he heard how Hitler and other dictators misused loudspeakers as a propaganda weapon.

The Dry Cell

Why not put a little wheat flour into battery electrolyte? That idea spun gold for the Danish amateur inventor Wilhelm Hellesen (1836-1892) when in the 1880s he made the world's first dry cell. He did this by using flour to turn the electrolyte into a paste, thereby making batteries easier to transport. In 1887, he established the Hellesen factory in Copenhagen together with Valdemar Ludvigsen, and by the 1890s the pair were exporting to over 50 countries.


August Krogh (1874-1949) was not the discoverer of insulin, but his contribution to the improvement of insulin production in Denmark was so considerable that he is considered a key figure in insulin history. One of the outcomes of his work was the establishment in 1923 of the Nordisk Insulin Laboratory, which later became part of Novo Nordisk. August Krogh was awarded the Nobel Prize in 1920 for the discovery of the capillary regulatory mechanism in skeletal muscle.

The Ostomy Bag

In 1953, Danish nurse Elise Sørensen hatched an idea that was both simple and ingenious. She took a disposable bag and equipped it with an adhesive ring to it so that the bag could be securely attached to the skin around a stoma, without the need for other dressings. Although her original device was somewhat primitive by today's standards, modern ostomy bags still utilize exactly the same principle that Sørensen invented.

The Lego Brick

There were many other children's building bricks on the market when Lego began making their distinctive plastic product in the 1940s. But no other manufacturer could make bricks that held together so well (while still being easy to separate) as Lego. In 1958, the company obtained a patent for the design of the brick, and since that time the product has gone from strength to strength. Today it is estimated that there are around 300 billion Lego bricks in use around the world.

Carlsberg's Yeast

In 1877, the microbiologist Emil Christian Hansen was employed in the Carlsberg Laboratory in the Copenhagen suburb of Valby. He soon discovered that yeast is composed of a number of different fungal species, which can be isolated into pure cultures. Hansen developed a brewer's yeast culture called Saccharomyces Carlsbergensis, which is used for brewing lager beers at the Carlsberg brewery in Denmark and at many other breweries worldwide.

The Fiberscope

The fiberscope is an optical instrument that can transmit an image to the eye through a fiber optic bundle, and has the advantage that the optic path can be curved without distorting the image. It can be used to visually inspect areas that are difficult to access by other means. The inventor was a Dane, Holger Møller Hansen, who obtained a patent in 1951.