The uses customarily incident to any of the above uses when situated on the same dwelling and not involving the conduct of a business, including the customary home occupations engaged in by the occupants of the dwelling and also including the office of a doctor, dentist, musician, artist or similar profession when situated in the same dwelling but said incidental use shall never be permitted as a principal use but only as a secondary use when indispensably necessary to the enjoyment of the premise for anyone of the use permitted in an “A” District and further provided that no name plate, sign board, or advertising sign of any nature exceeding two (2) square feet in area shall be permitted in an “A” District and not more than one (1) such sign if permitted to each residence.