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They must be able to Talk


By Sune Christian Pedersen

In the spring of 1801 the telegraph was introduced in Denmark. Not the electric one that we know with its Morse codes, wires, and bleeps. On the contrary a huge network of tall signal masts "from where the black tablets whispered their dead, but momentous language magically though the air" as Hans Christian Andersen poetically put it.


Posterity has chosen to call the technology causing so much commotion in 1801 "the optical telegraph": A telegraph operator, Johannes W. Steenstrup, narrates that "everywhere I came peasants credited this machine with supernatural powers". No wonder, considering that "a piece of intelligence carried by telegraphs can be conveyed by a speed approaching that of lightening" as he phrased it. In practice, according to his calculations the "lightening" was scarcely half an hour on its way from Copenhagen to Schleswig provided the weather was clear and the telegraph operators alert.

Fisker’s System
Signalling across distances was no news in itself. What was new were the ambitions of the inventors of the optical telegraphs – in Denmark a "Signal Commission" under the Navy, led by captain Lorentz Heinrich Fisker. As the naval officers saw it, the optical telegraphs should be able to "give expression to any occurrence, ask any question, give any answer, and issue any order, i.e.: they must be able to talk". Nothing similar had been seen before.

For the purpose an enormous apparatus was developed which by means of 18 flaps could display more than 42,000 different signals expressed in numbers. For each number there was a word or a sentence in a code book, e.g. "6943 = The enemy is attacking". In that way a single signal could "talk" about enemies in the proximity, departure of the mail boat, or the strait icing up. More complicated messages required more signals.

Later Systems
During the following 50 years different types of optical telegraphs were developed in Denmark. Generally, the telegraphs became easier and faster to operate realizing that the "hardware" itself – mounting and reading of the signals – were the weakest links in the communication process. Eventually, the enormous mast telegraphs had to yield to smaller and faster models which required more signals per message, but were all in all easier to work with.

The Optical Telegraph is Ousted
However, from 1854 the optical telegraphs had to yield to the electrical telegraphs which were introduced in Denmark that year. Only the optical telegraphs at the Great Belt were left, now heavily dilapidated, with the sole function of acting as stand-by for the vulnerable electrical telegraph line under the strait. In 1862, the last optical telegraph line was closed down and to the regret of Post & Tele Museum all remaining objects were sold by auction.

Footnotes:
The earliest telegraphs were developed by a signal commission appointed by the Navy. They had a striking similarity to ship’s masts. These "Mast Telegraphs" were erected along the Sound and from Copenhagen to Schleswig. During the years 1801-07 the telegraphs at the Great Belt were preserved under the orders of the postal service whilst the other telegraphs were dismantled.

In 1809 the so-called frame telegraphs were erected at the Great Belt and on the islands of Tåsinge, Langeland, and Falster. They could display more than 99,999 different signals. After the end of the Napoleonic wars in 1814 this type was preserved at the Great Belt under the management of the postal service.


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