A product responsible for the safe opening is critical. Because of such reason, this watch-like-mechanism is under a continous quality control during the whole manufacturing process. The mechanism model ref. 4100 is compatible with the main market existing brands. It can be coupled to different types of doors knobs as black, golden, chromed. The electronic models ref. 6110 (square) and ref. 6120 (round) have two different code combination from 2 to 10 digits. Electrical supply is given by 4x1,5 v. batteries. When a wrong code is entered three times successively, the system will remain blocked during five minutes.