The multiple light beam safety devices of the MLD 300 (type 2) and MLD 500 (type 4) series are used for access guarding at machines and systems. The devices are available as 2-, 3- and 4-beam transmitter-receiver systems for large operating ranges up to 70 m and as cost-efficient 2- and 3-beam transceiver systems for operating ranges up to 8 m.