Mechanical timepiece with posture detector

A mechanical timepiece comprising:

• a mainspring for generating a rotational force;
• a front train wheel for undergoing rotation in accordance with the rotational force generated by the mainspring;
• an escapement/speed-control device for controlling rotation of the front train wheel, the escapement/speed-control device having a balance with hairspring for undergoing reciprocal rotational movement, an escape wheel and pinion for undergoing rotation in accordance with rotation of the front train wheel, and a pallet fork for controlling rotation of the escape wheel and pinion in accordance with rotation of the balance with hairspring;
• a stitch mechanism for outputting an ON signal when a rotation angle of the balance with hairspring becomes a predetermined threshold angle or greater and for outputting an OFF signal when the rotation angle of the balance with hairspring does not exceed the predetermined threshold angle;
• a position-detecting device for detecting a position of the mechanical timepiece;
• and a balance-with-hairspring rotation angle control mechanism for applying a force to suppress rotation of the balance with hairspring when the switch mechanism outputs an ON signal in accordance with a position of the mechanical timepiece detected by the position-detecting device.