A safety relay is a mechanical power relay that follows safety standard IEC/EN 61810-1. There are two requirements for this standard. The first is what is known as force-guided contacts, which means that there is a single armature mechanically linking each set of contacts so that they open and close in one single motion. This structure ensures that when a normally open contact becomes closed, the normally closed contact will simultaneously open. The second requirement to meet this safety standard is that the contact gaps of any open contact must be greater than 0.5 mm throughout the lifetime of the relay. These points are significant, as they allow for the detection of welded contacts. For instance, if the Form-A contact welds due to over-current, a safety relay will not allow the Form-B contact to close. Thus, a logic circuit can be wired to monitor for this condition and alert the system when there is a failure.