The invention relates to a device for displaying an instruction, in particular a speed limitation, by a B14 or equivalent panel (1), the panel (1) comprising a flat circular front plate (2) with an instruction display area (5). In the case of a B14 panel, the digital value displayed can be modified by changing at least one modifiable character and the display area (5) comprises an opening (8) and the panel further comprises at least one flat movable support on which the substitution figures (7) are represented, the front plate (2) and the flat movable support being parallel to each other, the flat movable support being included in the template of the front plate (2), each substitution figure being able to be provided by an actuator facing the opening (8), the flat movable support or at least one of the flat movable supports being a disc rotatable about the centre thereof, the centre of the rotatable disc being laterally offset with respect to the centre of the circular front plate (2). The device is autonomous with photovoltaic power supply.