Se denomina bocina a un instrumento compuesto de una pera de goma y una trompeta unidos.Al presionar la pera, el aire sale por la trompeta, creando sonido.Antiguamente se usaba en los automóviles como señal acústica, siendo sustituido a partir de la década de 1920 por un elemento accionado por energía eléctrica.Del mismo modo la bocina es utilizada en vehículos como trenes, barcos, motocicletas o bicicletas, etc, variando de acuerdo a cada vehículo.

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A horn is a sound-making device that can be equipped to motor vehicles, buses, bicycles, trains, trams (or streetcars for North American cities), and other types of vehicles. The sound made usually resembles a 'honk'. The vehicle operator uses the horn to warn others of the vehicle's approach or presence, or to call attention to some hazard. Motor vehicles, ships and trains are required by law in some countries to have horns. Bicycles like trams, trolley cars and streetcars in many areas are also legally required to have an audible warning device, but not universally, and not always a horn.

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