This series of universal transfer switch is suitable for DC, AC 50Hz, voltage 500V and below circuits, as the main circuit or electrical measuring instrument switch and remote control switch of power distribution equipment; also can be used as servo motor and three-phase capacity of 5.5kW and below AC motor start, reverse or variable speed switch. The series of transfer switches have 21 to 18, 18, 21, 24, 27, 30, etc. according to the number of gears of the contact device, of which 16 and below are single-row transfer switches; 18 and above are three-row transfer switches. There are two types of protection: open type and protective type. There are four types of handles: knob, normal, machine and gun. According to the handle operation mode, it is divided into two types: self-recovery and positioning. The so-called self-recovery means that when the handle is moved to a certain position, when the hand releases the handle, the handle automatically returns to the original position. The positioning type refers to the position of the handle after the hand is pulled to a certain wall, and the handle remains in the position when the hand is released. The operating positions of the universal transfer switch are expressed in terms of angles, which will be indicated on the "positioning characteristics table" of the universal transfer switch.