Edelcrantz Telegraph
1794 · Shutter Telegraph · Work 124 of 1,871
An Edelcrantz shutter telegraph outside Stockholm: a small station hut standing in the open, on its roof a tall upright frame painted white carrying nine square iron shutters painted matte black in a three by three grid with a single larger tenth shutter above the middle column, each shutter pivoting open or closed within the frame against the sky, the shutters worked by cords running down into the hut where the operator sits at the lever frame with the code table, the apparatus outdoors above the roof.
- What it was used for
- Coastal defence and archipelago traffic. In late October or on 1 November 1794, the sources give both dates, a trial ran between Drottningholm and Stockholm; lines followed to the fortresses of Fredriksborg and Vaxholm, to Grisslehamn and across the Aaland sea, then Gothenburg-Marstrand, Malmoe-Helsingborg and Karlskrona with its sea forts. In the war of 1808-09 the staff came largely from the militia levy; from 1836 a military telegraph corps. Around 1809 a few dozen stations were working, about one Swedish mile apart; a message from Sandhamn reached Stockholm in ten minutes. The decisive use was the Finnish War of 1808-09; afterwards the stations were left to decay because, as Nordisk familjebok transmits the official reasoning, there were no important messages to convey; the staff were dismissed. Rebuilt from 1836 and opened to the public in 1837, traffic stayed insignificant, because signalling was possible only when the weather allowed.
- What was new
- Swedish sources themselves say the installation came into use almost at the same time as Chappe's; there is no priority to be had here. The difference was throughput. Nine shutters in three rows were read as a place-value number - units, tens, hundreds in octal, 512 values, doubled to 1,024 by a tenth shutter - and each of those numbers stood for a syllable or a word from a signal table of 20,080 expressions. One setting could therefore carry several letters, where Chappe's indicator needed two signals per word, and twelve signs a minute went through. Anyone quoting nine shutters and 1,024 signals together has the arithmetic wrong: without the tenth shutter it is 512.