Safety controller and input-output unit therefor

A safety controller in a building block configuration comprising a single IO unifying unit and an array of a plurality of IO units including IO circuits, said single IO unifying unit being connectable to said IO units;

• said IO unifying unit including an IO power-receiving terminal for receiving power from an external IO power source and an IO power distributing terminal for distributing said received power to said array of IO units after passing inside said IO unifying unit;
• said array of IO units including distribution mains that extend along said array and have a starting end connected to said IO power distributing terminal and distribution branch lines for supplying power from said distribution mains to each of said IO circuits inside said IO units;
• power shutoff means being provided to said IO unifying unit on upstream side of said IO power distributing terminal and to each of said distribution branch lines in each of said IO units for supplying power to said IO circuit through said IO unifying unit, said distribution mains and said distribution branch lines selectably in units of said distribution mains and said distribution branch lines.