A power-transmission-side control circuit causes a power transmission device to perform temporary power transmission when a switch provided in a power-transmission-side instrument has been turned ON, and performs ID authentication based on ID authentication information. Additionally, such systems reduce or eliminate the need for an application program to be present on a processing system when displaying data created by or for that application program, such as a document or video stream. A locking mechanism which has a locking pin coupled to the bottom member secures the top member in one or more stationary positions. The camera’s motion can be detected with sensors, such as gyroscopes, or the camera itself can be used as a motion sensor. In another embodiment, the radiator includes a generally helical dome-shaped radiation member powered by an energy source and a generally dome-shaped reflection member including a reflective surface facing the radiation member. Next to contactless transmission of power or data signals, the coupling between the first and second coil vary to provide a signal representative of the relative rotational speed of the first part of the bearing with respect to the second part.