Tongue Display Unit research. Researcher (Yohan Payan) placing a wireless, miniaturised Tongue Display Unit (TDU) in a model of a mouth. The TDU, first developed in 1999, stimulates the tongue with input from an external sensor, and is an example of a tactile vision subsitution device. This TDU is designed to fit against the palate and be secured to the teeth. The grid of electrodes will stimulate the tongue. TDUs can be used as pressure sensors for amputees and paraplegics, by surgeons carrying out operations, and by blind people. Photographed in the TIMC-IMAG Laboratory in La Tronche, France.