GB1262764A - Improvements in and relating to battery-powered clocks - Google Patents

Abstract

1,262,764. Transistor oscillator circuits. GENERAL TIME CORP. 1 April, 1969 [5 April, 1968], No. 17047/69. Heading H3T. [Also in Divisions G3 and H2] In a battery powered clock a synchronous motor is energized via a bi-stable switching circuit 102 (Fig. 9) driven by an oscillator circuit 101 the output frequency of which is controlled by a tuning fork. The oscillations of the fork are maintained by current pulses through a drive coil 105 when a transistor Q 1 is rendered fully conducting by a pulse derived from voltage induced in a pick-up coil 104 due to oscillation of the fork. The pick-up and drive coils are coaxially wound on a permanent magnet core (Fig. 8, not shown) and disposed between the tines of the fork. The oscillator circuit is self starting by virtue of a slight positive bias due to current through coil 105, R112 and the base/ emitter of Q 1 , and appearing at the base when the circuit is initially energized. The fork tines are thereby caused to deflect and induce a voltage in coil 104 which renders Q 1 more conductive and eventually Q 1 is driven into saturation. Capacitors 110 and 111 serve to shift the electrical resonant frequency of the circuit into the vicinity of the natural resonant frequency of the fork. C110 also reduces the possibility of spurious H.F. oscillations triggering Q 1 . The oscillator output is coupled via a capacitor 120 to a conventional bi-stable switching circuit 102. Each time a negative pulse is received via diodes 117, 118 the bi-stable circuit changes state and passes current to motor coils 113, 114 alternately.