Whenever any law or ordinance designates and describes a through street or a stop intersection, the duty of the City Engineer shall be to place and maintain one or more standard stop or yield signs on each and every street intersecting such through street or that portion thereof described and designated as such, and to erect and maintain a stop sign at one or more entrances to any such stop intersection as specified in the law or ordinances. (1950 Code, p. 192.)