FAQ02355 of Safety Limit Switches FAQ

A direct opening mechanism is one that forces open a welded contact by the direct force applied by the actuator (operating section) pressing down.
Safety components with direct opening mechanism (forcibly opened contacts) display the mark(^*) on their labels.

Direct Opening Mechanism (Forcibly Opened Contacts)

After the contacts have been forced open, the contacts have enough insulation between them to clear the stipulated impulse withstand voltage (EN 60947-5-1) when the specified operating force (corresponding to DOF) or stroke (corresponding to DOT) is applied against a force of 10 N applied to the contacts (equivalent to the contact weld force).