Guardmaster safety relays meet EN ISO 13849-1 and include six basic units. The relays have a single-wire communication capability that helps eliminate dual-channel connection between relays. Users can expand and cascade safety functions up to a SIL 3 rating using a single wire to connect between relays. AND/OR logic can be set via a rotary switch on the front of the relay for configurations including regional and global e-stop architectures.