Interlock System - Identification and localization of faults in interlock systems

Ref.-No. 4970

For the safe operation of electrical systems, emergency stop or interlock applications interrupt the power supply or put the system in a safe state (DIN EN 60204-1 and DIN EN ISO 13850). In many cases - especially in the case of complex systems - it is difficult to determine which system component triggered the emergency shutdown or whether there is a short circuit or interruption in the interlock line. The troubleshooting can then be very complex and generate high costs due to the stoppage of machines.

Keywords: Interlocksystem, Interlock, Notaus, Sicherheitskreis, Sicherheit, Lokalisieren, Interlock system, interlock, emergency stop, safety circuit, localize 

The interlock system uses Time Domain Reflectometry methods to identify and locate faults in the safety circuit. By using appropriate waveforms, the interlock system can use the reflected signal to determine if the fault is a short circuit or line break. In addition, the interlock system locates the error so that repair or release can be done quickly.

The new interlock system has a simple structure and can also easily be retrofitted to existing systems.

Commercial Application

The interlock system can be used in all systems that use emergency stop switches and automated safety switches. The larger a facility is, the more complex the troubleshooting process can be and the greater the benefit of the interlock system. Off-times can be significantly reduced.

Competitive Advantages

  • Simple setup
  • Low cost
  • Reliable detection and localization of faults
  • Differentiation of opens and shorts
  • Easy to retrofit
  • Helps to reduce off time and operation costs


Current Status

A German patent application was filed, international applications are still possible. The method has been experimentally verified. In the name of RWTH Aachen, we offer interested companies the opportunity to license and further develop the technology.

More Technologies in Electrical Engineering


PROvendis GmbH · Schloßstr. 11 – 15
D – 45468 Mülheim an der Ruhr
T +49 (0)208 94105-0 ·