A Time-of-Flight Watch was a device that would sound a chime or other device to alert a spotter to know that his ship's salvo was about to land. This would permit the spotter to more reliably discern his own splashes from any others that might be falling near the target, which would be essential in determining the corrections to apply.
The Royal Navy was trialling watches in 1908 that could be set to the given gun range, started when the guns fired, and ring a bell at the moment the shells should fall.
- Fire Control, 1908. p. 5.
- Letter in BTY/6 at National Maritime Museum's Caird Library.
- Admiralty, Gunnery Branch (1908). Fire Control, 1908. (G. 4023/08) C.B. 1126. At Admiralty Library, Portsmouth, United Kingdom.