Computer history LEOK:
Period 1964 - 1974

Source: Gedenkboek "LEOK 1950 - 1975"

The previous history

The initial work on digital techniques started at the Laboratorium Elektronische Ontwikkelingen Krijgsmacht (LEOK) in the System group 'Data Handling'. The 'state of the art' of electronics in the public environment was characterised by valves and relais until the introduction in 1958 of the transistor. The transistor as semiconductor could be used as switching element. In 1960, a number of projects reached their finishing phase at LEOK. This gave the opportunity to start building a knowledge position in the area of semiconductors.

In 1961, research started on the possibilities to use digital techniques. Experiments comprised different port switching techniques, adders, logic circuits, shift circuits and so on.
THe LEOK used components that were manufactured by other laboratories (e.g. the Physics Laboratory of the 'RijksverdedigingsOrganisatie TNO' (RVO-TNO) and the (NATO) Shape Technical Centre).

In 1962, the experience was used in a project for the Royal Netherlands Army. The LEOK was developing a 'vehicle test hardware unit', that could measure different vehicle characteristics (velocity, accelleration, brake distance). The facility could be used to calibrate other distance and velocity meters.
The information stemming from an impuls signal was processed by digital circuits based upon Philips circuitry components.
Many lessons were learned about 'timing'-problems in digital circuits and how designs had to take these effects into account.

Improvements in the circuitry timings were made in the next project for the Royal Netherlands Air Force (KLu).
The project which started in January, 1963, aimed to automate the altimetry in a navigation station of the KLu. The resources of the total RIVA (Radar Informatie Verwerkende Apparatuur = Radar Information Processing Equipment) project was quite large for the Laboratory, as it involved resources from both system and techology oriented groups.
The processing of the video-integrated information from the radar and the generation of control signals for the VI-antenna was done in a digital calculator.

Own designed digital calculator

The LEOK digital calculator had the following characteristics:

wire programmed, special purpose
one-address instruction code
parallel processing
interrupt facilities with priority levels
core memory:
- 512 program words
- 128 words 'live' memory
- 64 words 'dead' memory.
word length 17 bits
clock frequency ca. 100 kc/s
instruction times:
- add/subtract: 60 microsec
- multiply/divide: 420 microsec

The core memory was manufactured completely by hand. Instructions and constants were fixed wired. The circuitry used in the digital calculator was designed by the Physics Laboratory RVO-TNO.

DICON

The RIVA-project period can be regarded as the start of software programming at LEOK. Around that time, the first 'general purpose' digital computer was bought, called the DICON ('digital controller'). The design was done by Hollandse SignaalApparaten (HSA). The system had 192 addresses and each program had to be entered instruction by instruction using toggle switches. The first research that made use of the DICON had to do with the analysis of problems with digital servo's. For that reason, the DICON was equiped with some synchro A/D-converters and D/A-converters.

Simulators

The 'follow-up' of the RIVA-project was the 3D-simulator project for the Royal Netherlands Navy (period 1965 till 1970). The simulator had to inject simulated targets as well as clutter in the 3D-radar.

The simulator was used until 1975. A detailed description of the system concept can be found in ROERING, 10, 2, December 1973, pp. 64-77.

For the realisation of the simulator, a Ferranti computer was rented; this Hermes-computer ('germanium-logica') was installed in the beginning of 1966 and was in use till the mid of 1967. This system can be regarded as the first real general purpose computer on which LEOK programs were executed.

SIMREK

In March, 1967, the Ferranti SIMREK was installed as a project computer at the LEOK laboratory. The acceptance phase of the system could be described as "eventful". The Ferrantie was in that time period a modern 'military' computer. The Royal Netherlands Navy bought three of those systems. The (UK) Royal Navy bought several systems as well.

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