Stand-Alone Master Unit. 16 Digital Inputs. 4 OSSD pairs (SIL 3). 4 Status Outputs. 4 Test Outputs. Screw Terminal Blocks Stand-Alone Master Unit to control smaller machinery connecting with up to 4 safety devices, i.e. 1 safety light curtain, 1 e-stop, 1 magnetic sensor and 1 two-hand switch