ARRANGEMENT FOR SYNCHRONIZING TWO SIGNALS

1420012 Automatic control of speed PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 10 Jan 1973 [13 Jan 1972] 1262/73 Heading G3R [Also in Divisions H3-5] Motor speed is controlled so that pulses #o (5c) generated by the optical tachometer 3, 4 are maintained in phase with the reference pulses #i (5a) obtained from oscillator O and divider D, or alternatively obtained from an external source at E. The reference pulse train controls a waveform generator G which provides a sawtooth voltage z (5b) applied to one input of an OR gate. The other input of the OR gate is supplied with a waveform a (5d) consisting of pulses having a duration equal to the spacing between the pulses #o and reference pulses #i. Measuring circuit C consists of a 4- position counter which is increased by each reference pulse #i and decreased by each pulse #o and produces the output a (5d) which changes from +V to -V when the count changes between positions 2 and 3. The output d (5f) is negative when the count is 1 and positive for all other counts. The signal d is applied to an AND gate which takes its other input e (Se) from the OR gate to provide an output f (5g) which effectively consists of the larger of the signals a and z and the smaller of the signals e and d. The signal f is sampled in circuit s at the arrival instant of pulse #o to give a stepped output signal c (5h) which is used to control the motor by changing the energization of the motor or a shaft mounted brake. The arrangement may be used to control the output frequency of a voltage controlled oscillator (see Division H3).