01/30/2026
Ask The Expert with Schmersal! Question: What is the difference between a Manual and Monitored Manual reset for a safety controller?
Answer, from Devin Murray, BSEE, MBA, FS Eng (TÜV Rheinland): In some cases, a risk assessment may conclude that an automatic reset of the safety controller is not permitted. This means that after the safety device has been interrupted and reengaged, a second action (typically pressing of a normally open momentary pushbutton) must be performed in order for the safety controller to close its safety outputs. With a Manual reset, the safety controller is reengaged the moment the pushbutton is pressed providing a 0v to 24v transition; this is considered a Leading or Rising edge reset. A Monitored Manual reset will reengage once this pushbutton is pressed then released, providing a 24v to 0v transition; this is considered a Trailing or Falling edge reset. Because a manual reset can be converted to an automatic reset by situations such as a welded contact in the pushbutton, new standards such as ISO 13849 make specific reference to using a monitored manual operation when a reset is required.