This object is part of a collection relating to the history and development of calculating devices assembled by Assoc Professor Allan Bromley of Sydney University, comprising mathematical instruments, slide-rules, mechanical and electronic calculators, electronic analogue computers, computer components, kit computers, education computers, and associated ephemera.

Allan Bromley was a lecturer and researcher at the University of Sydney Basser Department of Computer Science from 1978 until his untimely death in August 2002. He specialised in Computer Architecture, Computer Logic and in particular the History of Computing. He was regarded as the world authority on Charles Babbage's Calculating Engines (instigating the building of the Difference Engine No.2 at the Science Museum London) and the Antikythera Mechanism and had extensive knowledge of calculators, analogue computers, logic, stereopsis, totalisators, clocks and time keeping and mechanical engineering.

This object was used by Bromley to illustrate the use of analogue devices in complex calculations in his chapter on Analogue Computing Devices in William Aspray, Allan G. Bromley, et al, 'Computing Before Computers', Ames, Iowa: Iowa Stae University Press. (1990)

Rangefinder converters (2), metal / masonite, made by E E & S, England, 1942

A flat rectangular board bounded by a metal edge and having a pair of parallel metal indicators. The board has a semi-circular polar grid laid out on it. It is a graphical device for plotting the position of an aircraft on a map given its bearing (the direction to it from the point of view of an observer), its angle above the horizon and the distance to the aircraft along this slant. It solves the vertical triangle giving the height of the aircraft and its position on the map for anti-aircraft artillery range-finder calculations.

In use it converts polar to linear co-ordinates. A sliding linear scale is graduated 1 - 40, i.e. 1,000 - 40,000 feet; and a logarithmic circular scale shows the radius to 19,000 feet, i.e., marked each 10 degrees from 0 to 5,000 feet, each 5 degrees from 5,000 to 10,000 feet, and each degree from 10,000 feet to 19,000 feet.

Made: 1942

Marked EE and S 1942, D and D No. 311 (one of models), 314 (other model).

2010/1/294

1942

30 mm

260 mm