Safety relays are devices that implement safety functions. They function like any other relay, receiving one signal and sending out another.
Their primary concern is monitor safety functions such as E-STOP, safety gates, light barriers, light grids, two-hand controls, pressure sensitive mats, speed, standstill and much more. They must always be designed in such a way that, if wired correctly, neither a fault in the device nor an external fault caused by the sensor or actuator will lead to the loss of the safety function.
Safety relays are distinguished by a variety of supply voltage ranges, the number of safety contacts, the number of terminals they have, and their method of actuation.