Flashboard
This was a device which permitted military observers to pinpoint an enemy gun location by observing gun flashes. With a single gun firing several differently placed observers could easily take bearings on the gun flashes and determine its location by triangulation. However, with multiple batteries firing continuously it was very hard for separated observers to be sure they were observing the same gun flash.[1] [2]
The flash board was devised to deal with this and comprised a buzzer and light for each observer mounted on a display board at the spotting HQ connected to each observers morse key. When depressed the key would cause an observer's specific light to flash and the buzzer to sound. Any buzzer could also be heard simultaneously by the other observers over the telephone via the open microphones of the telephonists located at the HQ. The observers also had tripod mounted sighting telescopes able to give the bearing of an item of interest, in this case gun flashes.
The sequence of operation was as follows:
Suppose there are three or more observers observing 5 batteries. Observer B might be the first to spot a particular flash and begins to sight his telescope on it and presses his key sounding his buzzer. The telescope has grid lines marked on it and once these are aligned on a particular flash, this enables the observer to make sure that the flash he observes is from the same gun each time. At each flash he depresses his morse key and this sounds his buzzer and illuminates his light in the HQ.
The officer in charge of the HQ flash board will then instruct Observer B to lead and silences the other buzzers. He also plots the bearing of the gun from B on the plotting table and decides where the gun on this line is likely to be. He instructs each of the other observers where to look.
Every time B sees his particular gun flash he depresses his key which flashes his light and his buzzer sounds at HQ, which is also heard by the other observers via the telephone line. When another observer, say C hears B's buzzer and simultaneously sees a flash he depresses his key to activate his light and sights his telescope on the flash. Gradually all three observers will be flashing in time with B with telescopes pointing at the flashes. At this point the Officer turns off B's buzzer. If all the other observers continue to flash in time with B then the Officer can be sure that all observers are seeing the same gun flash and the exact position can be computed by triangulation.
A mass artillery barrage can then be called up to destroy that gun position.
References[edit]
- ↑ Artillery Survey in the First World War.Field Survey Association, 1971, Sir Lawrence Bragg, Major - General AH Dowson, Lt Colonel HH Hemmings page 27
- ↑ Van Der Kloot, William (Summer 2007). "Lawrence Bragg's Role in the Development of Sound-Ranging in World War I" (PDF). The Ranger Journal of the Defence Surveryors' Association. 2 (15): 24. Retrieved 2 February 2017.
See also[edit]
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