World War 2, Western Australia, Rottnest Island, Coast Artillery Instrumentation, Encoder - Fall of Shot Mk 1

Overview

Encoder – Fall of Shot Mk 1 -The Encoder is a graphical instrument designed to combine the observations from two fortress observation posts to report the fall of shot in terms of a clock-code. Adjustments to the range and bearing were passed by telephone to the decoder operator in the battery observation post of the engaging batter

Historical information

The Rottnest Island Fortress Plotting Room is a semi-buried complex within the Oliver Hill perimeter, built in 1936-38 and expanded in 1942.
A Fortress Plotting Room was where information about naval targets was received from Fortress Observation Posts, plotted and the required information extracted and then acted on. There are smaller plotting rooms associated with Bickley Battery which received information from the the Fortress Plotting Room and Battery Observation Posts.
The Fortress Plotting Room contained a Range-finding Exchange (telephone), Fortress Plotters to track shipping targets on charts, Fall-of-Shot Indicators, Fire Direction Table, Ballistic Correction Calculators and other equipment to collate incoming information about the type of target and its range, speed and course.

Details

Details

Registration number
cwa-org-32-54-687
Contextual Information

This entry is based on research, documentation and technical drawings prepared by John Mercer during many years as a leading member of the Rottnest Island Military Restoration Committee and the Defence Heritage Interpretation Plan Group.

Australian Army Museum of Western Australia

Australian Army Museum of Western Australia

Organisation Details
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Encoder
Encoder - Fall of Shot Mk1
Layout
Layout of Oliver Hill Fortress Plotting Room
Plotting Room door

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