391 c driving in rotation clockwise mobile 391 and the single plate 393 b plate 393 a meshed with mobile 34 being disconnected because of click 393 c during the relative movement of mobile 391 with reference to mobile 34 pin 391 e raises hammer 36 such that cam 38 d of wheel 38 is no longer maintained in phase with mobile 34 nose 502 b of hammer 502 falls via the effect of spring f 502 between two columns of wheel 462 support surface 502 a cooperating with cam 38 d such that wheel 38 which carries hand 18 brings the latter to midday and nose 464 b of interlocking lever 464 falls between two columns of wheel 462 via the effect of spring f 464 a bringing stud 465 between push button 24 and bent portion 481 c the mechanism is then in state b defined in fig2 and shown in fig4 c the connecting member formed by hammer 36 and cam 38 d then no longer provides a connection between wheel 38 and mobile 34 switch 46 thus plays the part of control member and deactivates the connecting member in this state push buttons 24 and 28 are operational if push button 28 is pressed again lever 461 k tips and drives pawl 461 p this.