Here's a flyaround of a British WWII Mance Mark V Heliograph. "A heliograph (Greek: Ἥλιος helios, meaning "sun", and γραφειν graphein, meaning "write") is a wireless solar telegraph that signals by flashes of sunlight (generally using Morse code) reflected by a mirror". (Wikipedia) The Mance heliograph produced flashes by momentarily moving the beam off target by tilting the mirror. The British used the Mance heliograph from the 1870s to the early 1960s. http://en.wikipedia.org/wiki/Heliograph http://www.prc68.com/I/MkVHeliograph.shtml
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