Today's safety relays are distinguished primarily by their technological design:

Most important application of safety relays is in automation industries dealing with robotic cell set up.

Cut a few safety relays, turn off the fusion shield, and any fusion ship becomes an exploding fusion-bomb.

Heavy safety relays thudded dully; the instruments flickered under a suddenly rising surge of power-then they were calm again.

Safety relays monitor a specific function; by connecting them to other safety relays they guarantee total monitoring of a plant or machine.

These differ from conventional PLC types as being suitable for use in safety-critical applications for which PLCs have traditionally been supplemented with hard-wired safety relays.

Safety relays can be provided with muting functionality which enables the temporary disabling of the safety function to allow objects to pass through the light curtains without tripping the safety relay.

Safety relays must always be designed in such a way that - when wired correctly - neither a fault on the device nor an external fault caused by a sensor or actuator may lead to the loss of the safety function.