Even before the First World War, the streets were full of the noise of bulb horns, their louder derivatives powered by exhaust gases, and even wailing mechanical sirens and the gradually emerging modern electro-mechanical horns.
The horns contained a diaphragm, initially vibrated by a mechanical cam, but soon replaced by a more durable and reliable electromagnet. A practical horn was introduced in 1908 by Lowell-McConnell of Newark, New Jersey, USA. It was invented by one Miller Reese Hutchison, who went on to be Thomas Alva Edison’s chief engineer.
The term klaxon itself is derived from Klaxon Signals Ltd of Oldham, England, which, although it did not invent the device, was instrumental in its widespread use in Great Britain and its then colonial empire. The word klaxon has its origins in the ancient Greek word klazō, meaning “I shout”. However, the designers had a major problem to solve: the lack of electricity. Automobiles at the time did not have dynamos and batteries, making do with a magneto powering the ignition barrel. So the original horns needed their own battery.
One of the pioneers of klaxon development was the German company of Robert Bosch, with whom Messrs Laurin and Klement were already in contact at the beginning of the 20th century. But it was not until after the First World War that Bosch’s 1914 patent protecting its own electric horn system was put into practice. The tricky problem of poor audibility at longer distances was solved by a trick taken from organ design: a second built-in diaphragm amplified the pair of tones so that the honking car could be heard up to two kilometres away.
Excessive street noise, totally out of line with the then normal maximum speed limit of around 30 km/h, led to the idea of introducing a pair of horns: the driver should primarily use the quieter of the two, resorting to a more forceful warning only when absolutely necessary. This idea failed to catch on, though. Instead, in the 1920s a special horn for fire trucks began to be used, with a switch between a lower and a higher tone, mimicking the pure fourth interval of the traditional horn to announce “Fire!”