First Bosch horn type UI 12 from 1921

In the early days of the automobile, there were so few vehicles on the road that they had no trouble attracting attention. By around 1910, however, traffic in Germany had increased so much that legal regulations regarding “honking to issue a warning sign” had become necessary.

Squawking, awkward to operate bulb horns only fulfilled the purpose of warning to a limited degree, leading to the engineers at Bosch developing an electric horn, which they patented in April 1914. The outbreak of the First World War prevented the rapid roll-out of production, which finally took place in July 1921.

The new “Bosch horn” stood out in a number of ways: it responded immediately at the touch of a button, it was reliable, had low power consumption, an aesthetic design, and – its ultimate key to success – it produced a pure, well-rounded tone with a long range. The Bosch horn owed this tone to the principle of the “stopped flute pipe”, borrowed from organ building, in which a second membrane provided the harmonics and therefore ensured the pleasant timbre as well as the required volume. Advertising for the new product highlighted the clear advantage it had: stop making noise, warn!

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