Safety Relay: How Does a Forcibly Guided Contact Work

If an NO contact becomes welded, all NC contacts will maintain a minimum distance of 0.5 mm when the coil is not energized. Likewise if an NC contact becomes welded, all NO contacts will maintain a minimum distance of 0.5 mm when the coil is energized.
Refer to the following diagram.

The forcibly guided contact mechanism is a requirement of EN 50205 for Safety Relays.
Class A Safety Relays (i.e., all contacts are forcibly guided contacts) have the mark(*) on the nameplate.

Forcibly Guided Contact Mechanism (G7SA Safety Relays)