The invention relates to a printer having a paper transporting cylinder and a housing provided with a panel having a paper output slit. The printer also has a device for protecting against the penetration of dust and spray water. According to the invention, the device includes a wedge which, in a first position, closes the paper output slit when the printer is not in use, and, in a second position, opens the paper output slit when the printer is in use in such a way that paper can pass though the paper output slit. The invention also has a drive for displacing the closing wedge from the first position to the second position and back.