The transfer switch, also known as the combination switch, is an important electrical control component, widely used in various circuits and equipment. It achieves flexible switching and control of the circuit through its unique multi-contact and multi-position design.

The structure of the transfer switch typically consists of an operating mechanism, a contact system, a rotating shaft, a handle, and a positioning mechanism. The operating mechanism is the core for controlling the switch's conversion action, allowing users to conveniently operate the switch. The contact system is the key for achieving circuit connection and disconnection, consisting of several stationary contact seats embedded in an insulating housing and movable contacts in the movable bracket. The movable contact rotates with the rotating shaft and can contact or disconnect with the stationary contact at different positions, thereby changing the circuit's on-off state. The design of the rotating shaft and handle enables users to easily rotate the switch and achieve circuit switching. The positioning mechanism ensures the accurate connection and stability of the contacts when the switch is in different positions. 

In terms of the working principle, when the handle of the rotary switch is turned, the rotating shaft will drive the contact system to rotate. As the contacts rotate, they will come into contact or disconnect at different positions with the corresponding static contacts, thereby changing the on-off state and connection mode of the circuit. This design enables the rotary switch to switch and control between different circuits, devices or working states, meeting the needs of various complex circuits. 

Overall, the transfer switch plays a significant role in the field of electrical control due to its unique structure and principles. It not only has the advantages of small size, reliable performance, and convenient operation, but also can adapt to the requirements of different circuits and achieve flexible switching and control of the circuits.