23.9—Special requirements for complete devices.
Telephones and signaling devices will be considered nonpermissible if used under any of the followings conditions:
(b)
With unprotected openings in any of the explosion-proof compartments. This condition refers to any openings in these compartments, but especially to those equipped with removable covers.
(d)
If installed or connected otherwise than in accordance with the instructions furnished by the manufacturer.