If there were such a thing as an inventory of typical Swiss characteristics, the PostBus three-tone horn would have to be part of it. Along with the yellow colour of the vehicles themselves, it is the national bus company’s most distinctive badge of recognition, and very much characterizes the Swiss Post brand. Hearing the word “Postbus” reminds many people of school trips or holiday outings on winding roads, and leaves the three-tone “toot-to-tooot” ringing in their ears. Today, Postbus drivers still sound the horn regularly, everywhere from normal scheduled routes to special buses for wedding parties.  

Three-tone horn – original

Post horns have been in use since the era of the horse coach service. Stage-coachmen used them to announce the arrival and departure of their coaches. They used the tones of the major triad, but also a range of other tone sequences to provide additional information such as the number of coaches or harnessed horses. Sounding the post horn was considered an art, and the coachman became something of a romanticized ideal. Since the Baroque period, the melodies of the post horn have found their way into music. Later, it was to be the other way round: the tone sequence used today, C sharp - E - A, is derived from the overture to Gioachino Rossini’s “William Tell”.

Three-tone horn – Gioachino Rossini and the post horn

With the advent in Switzerland of motorized Alpine post in 1919, the post horn again became the subject of debate for the first time since the telephone and telegraph had taken its place. Because the narrow Alpine roads were used not only by Swiss Post buses, but also by an ever-growing number of private cars. Accidents were frequent, and Swiss Post decided that Postbus drivers should sound a horn to warn other road users about blind spots. But the range of the first hand-operated car horns was too limited, and the advice of a team of experts at Swiss Post was sought. This team commissioned the Paris-based company Cicca to build a three-tone horn with an electric compressor.

This resulted in the prototype of the Postbus three-tone horn, which is still built into the vehicles to this day. The first Postbus to take to the roads with such a horn was in 1924. The Second World War put a stop to the import of Cicca horns from France, so from then on, the licence to produce the horns alternated between three Swiss manufacturers.

The reason that so many people primarily associate the PostBus three-tone horn with mountain trips is simple: use of the horn is restricted to mountainous postal routes, which are designated by a yellow horn on a blue background. Today, however, nobody knows how many mountainous postal routes there are in Switzerland, because the cantons have been responsible for signposting since 1992 and there is no overall list of these routes. But everybody knows that Postbus drivers sometimes make an exception and sound the horn on other roads. This of course means that the buses have to be equipped with a horn in the first place, which is currently the case in about one third of the 2,500 PostBus vehicles.

Outsiders are often amazed to discover that three-tone horns are not part of the standard equipment included in Postbuses. However, the three-tone horns are not obsolete: PostBus equips 20-40 new vehicles with post horns every year. The Emmental company Moser-Baer is now solely responsible for their production. Because the number is manageable, the staff there build the PostBus horns by hand. Moser-Baer also repairs and cleans three-tone horns because they generally have a longer service life than the vehicles, which are usually replaced after 12 years.

PostBus disassembles the horns in all decommissioned vehicles. The reason for this is simple: the three-tone horn is a registered trademark and should be used only for its intended purpose in PostBus vehicles. This means that the horn has already been dismantled when PostBus sells older vehicles to used vehicle dealers. The fact remains: if you want to hear the three-tone horn in action, you should treat yourself to a trip on one of the PostBus mountain routes and ask your Postbus driver to sound the horn now and again – to the delight of passengers young and old.