hello to all .i have an idea to build such switch by using which i can activate one of three switch .the story is like this that i have to power supplies in my home and one electric generator supply so i want such circuit that automatically activate one of the three .for example i have supply 1 supply 2 and supply 3 .i want to remain with supply 1 but if goes down due to load shading so supply 2 should be automatically on and if it is also not available so the electric generator should be automatically activated .and one thing more that is in the absence of supply 1 my main circuit breaker should automatically be off