Synchronized contact watch

Claim 1

In a battery-powered electric wrist watch of the type in which the immediate power source for the wheels is an oscillatory balance wheel unit including a hairspring, the combination of: means associated with the hairspring by which the oscillation frequency of the balance wheel unit is dependent on oscillation amplitude over a working range of oscillation frequency, an electromagnetic motive unit comprising a relatively movable drive coil and multipolar permanent magnet for imparting an impulse to the balance wheel when current flows in the drive coil, one of said elements of the motive unit being mounted for motion with the balance wheel, a battery for supplying direct current to said drive coil, a make-break contactor connected in series loop including said drive coil and battery and comprising a conductive element moving with the balance wheel and a flexible conductive member at one end and adapted to be engaged briefly by said moving conductive element to establish a conductive state of brief duration at a pre-determined point in the motion of the balance wheel, a triode transistor having a control electrode and having its two other electrodes connected in said series loop to pass current of said loop when the transistor is in conductive state, and a time base unit comprising a piezoelectric crystal oscillator unit and frequency divider network having its output directly connected to the control electrode of said transistor to apply thereto a train of discrete pulses of fixed width and frequency to render said transistor intermittently conductive, whereby the duration of current flow in said coil upon each closure of said contactor is determined by thE coincidence of its conductive state with that of said transistor, thereby to control the amplitude and through it the frequency of said balance wheel oscillations.