First exhibit in the Royal Signals museum: a model of a 6-bit clacks.
The one at Blandford was part of an Admiralty chain between Plymouth and Whitehall, operating in the first half of the C19th and superseded by the electric telegraph. There was also a branch to Portsmouth.
EDIT: Sceptical? Some lovely people have checked the facts for you - please see the replies. 馃槂
