Bookreview: Hebel, Riegel und Signale

Hebel, Riegel und Signalehebel_riegel_signale_titel_sm

By Hans G. Wägli, Diplory Verlag, CHF 116, €107

During the 2018 IRSE Convention Hans G Wägli, SBB’s former press secretary, presented his book on the history and principles of Swiss Mechanical Signalling Technology. It is a copious volume at 476 pages, but provided you can read German, one well worth its price.

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Hans G. Wägli at the IRSE Expo in Biasca presenting his book

This comprehensive work conveys in a vivid and entertaining way how railways were operated quickly, safely and efficiently in the 19th century. It fills a gap in historiography of railway technology as part of the first industrial revolution. Since then, the described processes have largely been automated. But even today they are still based on the same principles.

In the 19th century, in the days of first the industrial revolution railways began to offer their transport services. More and more trains were operated. The increasing railway traffic required communication between moving trains and the stations, a clear control of the fixed plant and a coordination of all involved. The challenges were overcome with technology that was both novel and innovative at the time: railway signalling technology. It made it possible to control and rationalize rail operations, while at the same time freeing up capacity and reducing operating risks. Employing the technology of the time, it built on mechanics, on levers, bars and signals.

The reader can follow how thoroughly and systematically the processes of railway operations were analysed and mapped by mechanical means. The principles of that time are still valid today and are still used in digital railway control systems.

Many readers will not be familiar with the technology, except when visiting heritage railways and museums. But it is well worth pointing out that mechanical signalling installations have a wonderful capacity to visualize signalling principles in a clear and approachable way. You can touch and feel it and understand why we use terms as locking a set of points or a route. It is also why interlocking became a generic term describing many aspects of railway signalling, such as a verb describing a process where mutually hazardous system states are excluded, as well as a noun describing the signalling plant in a station etc. 

The fact that the book obviously focusses on Swiss/German technology and its history should not be a deterrent, because, quoting prof Jörn Pachl’s book review, “It is noteworthy that the early development preceding the German development in England is also described. Particular attention is paid to the circumstances leading to a departure from cascade locking with sequential dependencies based on the English locking system and the transition to the German locking logic based on route locking. This has so far not been described so clearly in any other work, up to the comparison of the notation of English and German locking tables, […] leading to a completely different type of interlocking.”

I have always found that understanding why “they do it differently over there” is just as important for a signalling professional’s development than being aware of the fact that that is the case. It opens your mind, if you let it, to alternatives for the gospel you were taught by your mentors, but also alerts you to some of the pitfalls that may be associated with adopting foreign products, as well as implementing new technology. 

Understanding “first principles” is important and that is why books like this one are well worth the price, even if it is a bit of a steep one. The book is richly illustrated and contains an impressive bibliography

One word of advice the author himself gave me at the convention, when ordering from outside Switzerland, pay attention to the rather large differences in posting and packaging charges of different sources.

For a closer at the book look visit 

That site also offers a preview of the book, 

and as inevitably printing errors will occur, also refers to the errata:

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