A system measures a change in position of a medical appliance, such as an endoscopy capsule. A device uses this measurement in order to influence the position of the medical appliance. The medical appliance sends a signal that is received by a multiplicity of spatially separate receiving devices. The time profile of the phase differences between the received signals and a reference signal provides an indication of whether the medical appliance has moved. In the event of a movement being detected, a maneuvering device can be regulated by a regulating means in such a way that the maneuvering device generates forces and/or torques and applies them to the medical appliance to counteract the detected movement.
