The Computer

Elliott 920C

In 1969 Explorer was fitted with an Elliot 920C computer making her one of the first non military vessels to be so equipped, although it was a militarised version that was fitted probably to cope with the tough marine environment.

Elliott 903

The Elliot 920C was a “military” version of the Elliot 905 series computers.  Opposite is a photograph of the commercial Elliot 903 exhibit at the National Museum of Computing near Bletchley Park.  The military version, the 920B was used in the Nimrod maritime reconnaissance aircraft.  The more advanced 920C as fitted to the Explorer was the military version of the Elliot 905.

The following article from the Press and Journal, November 5th 1968 gives an insight into the purpose of the computer on the FRV Explorer as well as an indication as to when it was installed. Apologies for any typos.

FRS Explorer soon to install a special computer to further fishing gear research.

Previous articles in this annual series have touched on various aspects of Aberdeen Marine Laboratory’s programme. Work continues in many of these, along with new lines of development, and the staff like to think that many of them are of direct or indirect interest and value to the industry. But undoubtedly that which is of most immediate interest, as is shown by the the steadily increasing number of enquiries reaching the laboratory, concerns fishing gear itself-on which the laboratory’s small fisheries’ engineering unit has been concentrating during recent years.

One of the laboratory’s pioneer efforts was to use an echometer to see something of the shape of the trawl when it is on the seabed. Since then underwater photography and television have also been used but, in order to understand how the conventional gear operates, with a view to improving on it, it is quite essential to have precise measurements of tensions, distances, angles and so on in the many types of trawls, seines and hybrids between them, which are now in use.


During the last few years therefore, a number of monitoring instruments have been developed at the laboratory or acquired from other sources for measuring (usually continuously) with maximum precision just such parameters, both in conventional gear and in experimental modifications, so as to understand more fully what the effects of the changes are likely to be and how nets can best be adapted either to catch more fish or to catch the fish more economically.

As members of the industry in contact with the laboratory will know, a great deal of information has emerged from these experiments but there has always been one snag-that, even when made with many ingenious continuous-recording instruments, the results of the experiments have to wait analysis after the gear has been brought back on deck, and often enough await detailed analysis after the particular experimental cruise has been completed.

Sometimes several months might elapse before the results of a series of experiments could be properly assessed.

In order to resolve this and several other problems, the department have on order for the laboratory a specially adapted Elliot MCS 920C computer for incorporation in a data-logging and processing system on the research vessel Explorer.


It is hoped that the system will be installed in January. Its initial application will be to further fishing gear research although it can be used in several other aspects of the laboratory’s work.

For this new process a number of the existing monitoring instruments have been adapted for “communicating” with the computer, and new equipment has been obtained-all for measuring the performance of the ship and its gear, and their interaction, in different sea states, and when towing over different types of sea-bed.

For this purpose extensive tests have been proceeding in preparation for the installation of the computer, and computer programmes are being developed.

An attempt to resolve another problem is being made by developing an acoustic link system for communicating between the instruments on the fishing gear and the computer in place of the rather cumbrous systems which have been used hitherto: improved types of conducting cable systems using special warps are also being developed.

In addition to monitoring the various elements of the fishing gear itself, information from the instruments for measuring wind, ship speed, thrust and motion characteristics and other parameters connected with the engine room and navigational aids are all being provided to feed information to the computer.


Thus, all these factors can be taken onto account at once, and the very complex series of data largely processed at almost the same time as it is being measured.

In this way it is hoped that the scientists will be able to monitor performance continuously and take correcting action when necessary during the course of a cruise.

This new step will allow the vast amounts of information to be available for scientific study much more quickly and, of course the results passed to the industry more speedily.

Indeed, it is hoped that this new system will demonstrate something of the feasibility or otherwise of using some of the various components in simpler fishing systems.


Of particular importance in this connection are the navigational, fish finding and unnamed engine-room applications

The use of a computer at the centre of a data logging system provides enormous flexibility as compared with traditional data logging systems and it may even be that smaller or simplified processors will become a normal part of trawler equipment in the future.

Certainly it should speed up gear research considerably. And the apparatus can also be used in other branches of the laboratory’s work-from studying the sea itself to other aspects of research on the fish.

Credited to The Press and Journal

A Potted History of the 900 series Computer
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