The display unit (1) includes a first display (3) facing an observation position and a controllable second display (6) lying in front of the first display. The latter is transparent in its de-activated state so that there is no hinderance in the view of the first display. In the activated state, the second display shows numbers or letters, using a matrix of liquid crystal cells. Between the displays, at the rear of the second display but out of sight to the side is a lamp (7), used to activate the cells. Between the displays is also a diaphragm (4) which can be switched between transparent and opaque states.
