The Heliograph was a simple but highly effective instrument for instantaneous optical communication over 50 miles or more in the 19th century. Its major uses were for military and survey work. It was still in serious use at least up to 1935, for example by Glubb Pasha's Arab Legion in Palestine.
The heliograph sent its signals by reflecting sunlight towards the intended recipient with a mirror or mirrors, the beam being keyed on and off with a shutter or a tilting mirror, allowing Morse code to be sent. Heliographs were used by the armies of several countries during the late 1800's; they were highly popular with British forces in India because of the dependable sunlight.
The classic heliograph is the Mance pattern, devised by Sir Henry Mance at Bombay in 1869. See illustration below.
illustration 1: A British Mark V Mance pattern 5-inch heliograph. The operating key is behind the mirror.
The heliograph had some powerful advantages. It allowed long-distance communication with no fixed infrastructure. It was highly portable, required no power source, and was relatively secure in that it was invisible if you were not close to the axis of operation.
On the minus side, the heliograph was obviously vulnerable to bad weather, and the mirrors were fragile.
(the article above is an edit from http://www.dself.dsl.pipex.com/MUSEUM/COMMS/heliograph/heliograph.htm from 'The museum of retrotechnology' A wonderful storeroom of technology and ideas. The article was placed without permission and will be removed on simple demand)
No comments:
Post a Comment