Vehicles, Background

Du-Da-Do sounds from the air-raid shelter

Exactly 100 years after its introduction, the Postbus’s Du-Da-Do still sounds from three brass bells. The post horn is handmade in Emmental. A look behind the scenes – and into the air-raid shelter where they are tuned.

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Post horn production video

Three metal trumpets connected by an aluminium compressor make up the post horn. Mounted on the underside of Postbuses, they are activated by a compressor to warn oncoming vehicles at a volume of 120 decibels and prevent collisions. 100 years ago, in 1924, the first Postbus sounded the Du-Da-Do horn. Around 700 Postbuses, used mainly in mountain regions, are still equipped with the horn to this day.

PostBus has to order up to 30 new post horns every year. Their shot-peened and nickel-plated surface resists moisture, salt, cold and heat. This means that the horns have a long service life and are always removed from old Postbuses and installed on the new ones. When an old Postbus is resold, the post horn is removed beforehand. That’s because Du-Da-Do is inextricably linked to the PostBus brand.

Two public transport icons

It takes a lot of experience and skill to create the unmistakable three-tone horn. The mechanics involved assemble 80 individual parts by hand in a single working day. Moser-Baer AG, based in Sumiswald in the Emmental (Canton of Bern), has been the exclusive producer of the post horn for 70 years. The company has evolved considerably, now earning 90 percent of its income from exports and specializing in medical technology and time systems. The three-tone horn, which costs 2,000 francs a piece, is a small niche product in their range.

Another public transport icon has a slightly more notable appearance: SBB station clockTarget not accessibles are manufactured and assembled under the MobatimeTarget not accessible brand in the same premises as the post horn.

Hearing protection included!

Damaged horns also end up on René Schaffer’s workbench in the metalworking shop in Wasen for repairs. «They should be used as often as possible, because the dirt particles are also blown away when the horn is sounded. This means that they can provide decades of service,» says the mechanic at Moser-Baer. One thing is sacrosanct: no horn leaves the company without being tuned. The A major triad «C-sharp–E–A» from Gioachino Rossini’s overture to «William Tell» must sound crisp.

To tune the horns without damaging his colleagues’ hearing, René Schaffer regularly goes down into the air-raid shelter. Behind three thick doors and protected by earplugs and Pamir headphones, he uses a measuring device and a clock to check that the triad’s sequence of notes, volume and speed are all correct. Even his colleagues in the workshop upstairs can still hear the Du-Da-Do. «It’s music to our ears. The post horn isn’t only a piece of Switzerland, it’s also a part of our company,» says Janos Horak, Head of Production for clock systems and post horns at Moser-Baer AGTarget not accessible.

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