The general field of the invention is that of capacitive dongles used with visualization devices including a capacitive touch-sensitive surface comprising a matrix of conductive rows and columns, the dongle being arranged on said touch-sensitive surface in operational use, the dongle operating in send mode and in receive mode, The dongle according to the invention includes: means for sending periodic analogue signals sent at a specific frequency known as the dangle frequency; a ring-shaped flat conductive metal part connected to said sending means, said part intended to be placed on said touch-sensitive surface; means for receiving the received signals output by said conductive metal part; means for analyzing said digitized received signals; means for storing the sent and analyzed signals; a digital communication interface.