A trailer coupling for motor vehicles able to be moved from a working position to a resting position and the reverse. The burner assembly includes a burner pot, a combustion mat, a pot cover, and a burner frame. Two interferometric outputs i1 and i2, where the phase difference is 90 degrees from each other, are obtained by interference of the reference pulse and the signal pulse. The group can control the movement of an avatar in a virtual space based on the movement of each person in the group, such as in a steering or balancing game. The instrument is then detached from the device.