Digital Technologies: Traversing Unit Test equipment (TUT) (1982)


Traversing Unit Test Equipment (TUT)

In 1973, the Royal Netherlands Army purchased 156 single Raytheon Missile Systems’ BGM-71 TOW anti-tank missile launchers. In the early 1980s, an additional 277 dual Tube launched, Optically tracked, Wire data link auto-guided missile (TOW) systems were installed on the Dutch YPR-765s and DAF YP508 PWATs. The TOW is designed as an anti-tank missile. Later TOW versions included bunker busters.
The TOW weapon was used by the Dutch Army until 2005.

Transports and deployment during exercises and deployments could potentially disrupt the proper functioning of these missile launchers. In 1982, the Army’s Material Supply Department 2 (MVA2 – electronic equipment), therefore, commissioned the TNO Physics Laboratory to develop the prototype of a missile launcher test device. The test device had to be able to test the proper functioning of TOW launchers.

The TOW rocket with the unfolded front and rear fins
The TOW missile with the unfolded front and rear fins


The TOW gun carriage with mounted directional equipment
The TOW gun carriage with mounted directional equipment

The test device Traversing Unit Test equipment (“TUT”) developed by TNO was designed to test every electrical connection between a TOW and the launcher. The correct spring pressure required for loading the TOW rocket could also be measured. The TUT was the first device developed by TNO based on a microcomputer and printed circuit boards (PCBs). The PCBs were hand-wired; the Integrated Circuits (ICs) were placed in IC sockets. The prototype, therefore, did not meet military requirements.

The TUT consists of four parts:

  • An Intel 8751 microcomputer with a power supply and a display. This is placed in an empty TOW missile tube.
  • Rifle scope support with cable. This rifle scope support was fitted as a cheap replacement for the TOW infrared range-finder equipment.
  • Rifle scope.
  • Transport box for the TUT. This transport box also served as a screen to align the TUT.
The block diagram of the TUT
The block diagram of the TUT


Empty TOW launcher tube with the TUT
Empty TOW launch tube with the TUT


Rocket launcher tube with TUT placed on a gun carriage
Rocket launcher tube with TUT placed on a gun carriage

Measuring the connections was not limited to testing the interconnections but included an insulation test for the close-by wires in the cables. The conductivity (resistance) of each connection was also measured. Moreover, the pressure was measured under which a TOW rocket was secured in the launcher.

The following buttons and indicators are used in the measurement procedure on the TUT unit:

  • TOW TEST:  button to start the tests
  • CONTINUE:  button to initiate next test
  • CONTINUE (blinking led): initiating next test
  • ERROR (blinking LED): error detected during a test
  • MEMORY (blinking LED): more information is available
  • MEMORY: pressing the button causes the display of additional information
  • AZIMUTH/ELEVATION meter: shows the polarity of these values

The LCD (display) shows the status of the individual measurements and blinks if a low battery voltage is detected.

The following test sequence takes place:

  • spring force measurement
  • insulation test
  • conductivity measurement
  • trigger test
  • azimuth and elevation measurement of the gun carriage
  • wire-cutter test

If the TOW placement pressure is larger than the reference pressure during the spring force measurement, the TUT switches off. If errors occur during the ongoing test sequence, the test sequence is not interrupted but stored to be assessed at a later moment.
The trigger test replaces the firing button of the TOW. The wire cutter replaces the actual cutter that is used when the missile approaches the target after the unwinding of the guide wires.