The utility model relates to an improved control switch, in particular to a compound switch used for a transformer cooler. The present technology has the problems of that a contact apparatus is prone to be burnt out and the operation is unreliable. The utility model has an input terminal and an out terminal; wherein, a controllable silicon switch and a magnetic latching relay are arranged between the output terminal and the input terminal in series; the controllable silicon switch and the magnetic latching relay are connected with a signal processing module; the circuit of the signal processing is provided with a control signal input interface. Through the smart and skilled combination of the controllable silicon switch and the magnetic latching relay, the compound switch has the advantages of high voltage bearing and large volume of the control silicon switch during the short periods of switching on and cutting off; furthermore, while being normally connected, the compound switch then has the advantages of no power consumption on the contact apparatus, steady and reliable operation and long service life.