When the city power cut, to protect mistake, ATS takes only 5 second for confirmation,within this 5 seconds if the city power not come,the generator will start by itself, when the starting motor is running, the ATS checking the speed of generator engine, when the starting is successful,the engine get back immediately,so that it will be not broke, generator set starting not supply power immediately,but running without any load for 30 seconds (this period can be fitted by the customer requirement) then supply power again