The actress and the torpedo

German-speaking nations celebrate Inventors’ Day on 9 November, which is the birthday of actress Hedy Lamarr, the glamorous and seductive star of many Hollywood movies of the 1940s.

Hedy Lamarr was born Hedwig Kiesler in Vienna in 1914. As a teenager she played major roles in German films, but in 1933 she married a Vienna-based arms manufacturer, who put a lid on her acting career. Instead, he took her with him to business meetings with Nazi industrialists. In 1937 she fled Austria, secured a divorce and met the film producer Louis B. Mayer, who took her to Hollywood.  

A neighbour in Tinseltown was the film score composer George Antheil, the son of German immigrants. His many non-musical interests included endocrinology, and it seems that Lamarr first met him when she approached him for advice on breast enlargement. Somehow their initial conversation moved on from boobs to bombs.

The intelligent young actress had acquired a knowledge of military technology from her ex-husband’s business, while the composer had experimented with the automated control of musical instruments. Together they went on to devise a secret communication system for radio-guided torpedoes, using a piano roll to change between 88 frequencies, thus making it hard for enemies to detect or jam the radio signals.

(The number of frequencies was determined by the piano roll’s more usual function of controlling the 88 keys of a player-piano.)

The invention attracted the US navy’s interest, but technology was not then advanced enough to make it feasible. The system was eventually implemented during the 1962 US blockade of Cuba.

Nowadays frequency-hopping spread spectrum systems are widely used in transmitting radio signals and they are integral to mobile telephone technology. Their benefits include a great resistance to narrowband interference and a highly efficient use of bandwidth.

Hedy Lamarr gained no fame or fortune from her contribution to radio communication and for about 50 years she received little recognition. So it is to the credit of the inventors of Inventors’ Day that they have chosen to acknowledge her in this way.