Mechanical timepiece with timed annular balance rotating angle control mechanism

A mechanical timepiece comprising:

• a power source comprised of a mainspring for undergoing rewinding movement to generate a rational force;
• a front train wheel for undergoing rotation in accordance with a rotational force generated during rewinding movement of the mainspring;
• an escapement/speed-control device for controlling rotation of the front train wheel, the escapement/speed-control device having a balance with a hairspring for undergoing alternatively repeating rotational movement in left and right directions;
• an escape wheel and pinion for undergoing rotation in accordance with rotation of the front train wheel;
• a pallet fork for controlling rotation of the escape wheel and pinion in accordance with rotational movement of the balance;
• a switch mechanism for outputting an ON signal when a rotation angle of the balance reaches a predetermined threshold angle or greater, and for outputting an OFF signal when the rotation angle of the balance does not exceed the predetermined threshold angle;
• and
• a rotation angle control mechanism for suppressing rotation of the balance when the switch mechanism outputs an ON signal.