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Electromechanical Detectors—EU Cautor and Forfex


A track mounted train detector used to detect the passage of a train or single vehicle travelling at speeds up to 260 km/hour.

The CAUTOR and FORFEX system detects the presence of a train travelling along the track and controls all functions related to its passage.


  • Level crossings (control of gates and lights).
  • Signal control.
  • Axle counting.

Principle of Operation
Inside a cast iron housing, are torsion bars (one for each direction in the case of a Forfex Treadle) in high-tensile stainless steel which absorb the energy produced by the shock of the wheel on the arms and control a mechanical interlock. The latter selects the electrical contact to be operated according to the direction of travel of the train. This ensures an adequate period of closure of the contacts whatever the time-constant of the circuits controlled.

The devices are installed using a support fitting clamped to the base of the rail. There are three types of support fitting:

  • Flat Bottom Base suitable for Rail 109lb and CEN60 Rail (As shown on Cautor Treadle above)
  • EU Base and Adapter suitable for Flat Bottom Rail (As shown on Forfex Treadle above)

The devices require a 6 Core Treadle Lead with SNCF Connector and Preformed 6 Way 2 BA Connector, supplied in 4 different lengths.

Additional Technical Information Is Available On Request.

Cat Numbers

Forfex Std

Forfex A-B
Forfex B-A

EU Base


Henry Williams Limited

Dodsworth Street
County Durham

Email: Please use form opposite.
Tel: 01325 462722
Fax: 01325 245220

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About Henry Williams

The story of Henry Williams Limited goes back to 1883, when the company was formed to manufacture control and signalling equipment for the rapidly expanding railways network. Since those historic and pioneering days, our skills have broadened, our technology has advanced with the time and our sphere of influence has widened more

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