PL d safety interfaces for emergency stop buttons and safety switches Safety relay for emergency stop buttons and safety switches monitoring. Guided-contact safety relays 2 N.A. + 1 N.C. EDM Feedback input for external contactors monitoring. The Start/Restart can be: automatic/manual (AD SRE3) or manual monitored (AD SRE3C). Both models can be used up to safety Category 3, PL d according to EN ISO 13849-1. Product certified by TUEV Nord Cert GmbH.