Abstract: A human-machine interface includes a panel formed of energy transmissive material having a contact surface on which one or more contacts may simultaneously be made. An energy source directs energy to the panel. The panel transmits energy received from the energy source to the contact surface. At least one parameter of the energy transmitted by the panel is altered at regions where contacts are made with the contact surface. A detector is coupled to the panel and detects the at least one parameter of the energy generally over the area of the contact surface and outputs values corresponding thereto. A processor is in communication with the detector. The processor processes the output values to determine the locations of the contact regions on the contact surface.