Horn

Horn:
A horn (also called a hooter) is intended to give a danger signal on, among other things, cars and trucks. The first horns were used on American cars in 1908. A short time later they were also introduced in the Netherlands.
A horn often produces a monotonous sound, but there are also multi-tone horns in use. Multi-tone horns are prohibited in the Netherlands. The horn must emit a constant tone. When 2 horns are mounted next to each other, each providing a different sound level (one for the high and one for the low tones), these horns must switch on and off at exactly the same moment, so that it still seems like it is 1 single tone.