Concentration Signals

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The Royal Navy used a variety of visual methods to help multiple ships concentrate their fire upon a single target.

Visual Training Marks

The Royal Navy would paint hash marks on the sides of some turrets to permit nearby ships to see the angle of training.


A ship could indicate the range it was firing to on large indicators mounted on its tops. Two basic designs for these displays were used: drums and dials.

Range Dials

Main article

These generally took the form of one or two dials of 4- to 10-feet in diameter with hands arranged to indicate the gun range. Often, the gun range was decomposed by separate hands indicating 100s, 1000s and 10000s of yards. Simple mechanical levers were used to transmit the hand positions.

Concentration Drums

Prior to the pre-eminence of the dial-based designs, a few ships briefly had cylindrical drums which indicated the range in a digital manner. These designs were found to be much harder to read.

See Also



  • Schleihauf, William (April, 1998). "A Concentrated Effort: Royal Navy Gunnery Exercises at the End of the Great War." Warship International 35 (2): pp. 117–139.
  • Manual of Gunnery in H.M. Fleet, Volume III, 1920.