Background

The purpose of this tower was to send messages between the Admiralty in London to the Dockyard at Portsmouth. This tower was one of 10 such towers forming a Semaphore Line. Other Semaphore lines linked the Admiralty with other important naval ports.

This system of optical communication was first proposed by Robert Hook in 1684 who described visual telegraphy to the Royal Society. This however was never taken up at this time.

The first implementation was in 1792 when Claude Chappe created 556 stations covering France. The French system used angled rods to communicate between stations. To secure the communications, a code book was produced which was used to interpret the signals.

The implementation in the UK began in 1795, stimulated by reports of the French system. The following Semaphore lines were established:- Liverpool-Holyhead; London - Deel & Sheerness; London - Great Yarmouth; London - Portsmouth and Plymouth. The UK implementation used boards with six large holes which could be closed by shutters.

The tower is open to the public on Sundays in summer, and contains hands-on working semaphore models and displays on the history of overland naval communications in the early 19th century.

References and further reading:-

1) Semaphore Line (Wikipedia)

2) Chatley Heath Semaphore Tower (Wikipedia)