Come to think of it, why does the second hand of the Swiss railway clock pause at 12?
Background information

Come to think of it, why does the second hand of the Swiss railway clock pause at 12?

Carolin Teufelberger
Zurich, on 03.11.2021
Translation: Veronica Bielawski

The Swiss railway clock is iconic. Pure black and white minimalism challenged only by the red second hand. The second hand doesn’t just stand out because of its colour, but also because it stands still at every full minute.

A cool gust of wind blows across the platform; an ICE train has just blazed by. I’m waiting for the Interregio that will take me from Lenzburg to Zurich. Six more minutes... Instead of staring mindlessly at my phone, I decide to play a little guessing game I like to call «When’s the minute over». The station clock will be my judge. As soon as the second hand reaches twelve, it’s time to start counting. Or not. Because once it does reach the twelve, it first stays there for a moment before beginning a new rotation. Why’s that?


Punctuality is a must

The year is 1944. Engineer Hans Hilfiker, who has been working for SBB in Bauabteilung III (SBB’s construction department) for twelve years, is promoted to deputy head and drafts the now-iconic Swiss railway clock. The design is simple: black lines on a white background with a black hour and minute hand. There are no numbers on the clock. That way, you can read the time even from a larger distance.

Hilfiker wants all railway clocks in Switzerland to run synchronously so that trains depart on time from every station. To achieve this, a master clock is needed to send out an electrical impulse every minute. The impulse is transmitted via telephone cable. It’s sent from the master clock in Zurich’s signal box to all other railway clocks in Switzerland.

In 1947, the red second hand is added to the clock. Hilfiker designs it to match the style of the signposts used by train dispatchers. He wants passengers to be able to see just how many seconds are left until departure. But this poses a technical challenge for the company Moser-Baer, which has been manufacturing the railway clocks since 1944. The problem: at this point in time, it’s not yet possible to run a clock mechanically with impulses by the second. The solution: the second hand is instead controlled by the minute impulse. To ensure that frequency fluctuations in the power grid don’t affect overall accuracy, the second hand is accelerated and completes a full rotation in 58.5 seconds. This ensures that – should the frequency drop below the normal 50 hertz – the second hand still makes it to twelve ahead of the ‘minute’ impulse.

Cult status

Today, this is no longer really necessary, since the clocks run on signals that are exact to the tenth of a second. But the small pause as the second hand marks a new minute has since become a distinguishing feature of the Swiss railway clock. It’s a big part of what makes it iconic.

Since 1986, there’s also a wristwatch version of the Swiss railway clock, manufactured by Mondaine. Even Apple briefly added Hans Hilfiker’s watch to its iPhones and iPads on iOS 6 – without a license, mind you. The agreement with the SBB was reached only after the fact, and reportedly brought in 20 million Swiss francs for the SBB.

In the meantime, my Interregio has arrived. Right on time. I learned a fair bit while waiting. Admittedly, I did end up staring into my phone. But I now know why the second hand of the Swiss railway clock is the way it is. Oh, and I found out I have an abysmal sense of time. According to me, one minute is exactly 41 seconds long. What can I say? I’m livin’ la vida rápida.

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Carolin Teufelberger
Carolin Teufelberger

Editor, Zurich

My life in a nutshell? On a quest to broaden my horizon. I love discovering and learning new skills and I see a chance to experience something new in everything – be it travelling, reading, cooking, movies or DIY.

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