Connection detection system, device and method related to connection structure

The present invention relates to a connection detection system, device, and method for a connection structure, capable of automatically detecting this situation when a first device is attached to a second device, and capable of recognizing the first device, and disclosed is a connection detection system configured to include the first device and the second device, the first device including: a first connection terminal including a first connection terminal, a second connection terminal, and a second connection terminal; the first terminal is provided with a first-1 contact and a first-2 contact. And a first reactance element connected to the first connection terminal. The second device is provided with: a second connection terminal having a second-1 contact and a second-2 contact corresponding to the first-1 contact and the first-2 contact; a first resistance element; a first frequency generator that applies a signal, the frequency of which changes within a predetermined range, to the first device via the fir