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But in his later Edison, what ever may be circuit size we can operate with minimum power. It is so efficient and occupies less space. Due to this devices, all electrical equipment size getting reduced.Cost of this device is also low compare to other mechanical equipments. Power electronics is the emerging field, where all the power engineering equipments are controlled by this simple devices. There are many improvements in this devices so that it can operate automatically without external operator. This will be discussed later.