Radio synchronized time-keeping apparatus and method

• US 4,234,958 A
• Filed: 06/16/1977
• Issued: 11/18/1980
• Est. Priority Date: 06/16/1977
• Status: Expired due to Term

• Current Assignee: Lathem Time Recorder Company Incorporated
• Original Assignee: Lathem Time Recorder Company Incorporated
• Inventors: Millsap, Roy V., Hooper, Harrison G., McClure, Richard W., Pipes, William F.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/807,011
• Time in Patent Office: 1,251 Days
• Field of Search: 178/69.1, 179/15 BS, 325/58, 325/321, 325/325, 325/363, 331/172, 343/225, 340/146.1 D, 340/147 SY, 58/35 W, 375/106, 375/107, 375/118, 370/100
• US Class Current: 375/356
• CPC Class Codes: G04R 40/00 Correcting the clock frequency

Abstract

A synchronizer comprised of a combination of integrated circuits including logic gates, latches and counters designed to interface with a master time controller to provide a means of linking the accuracy of the time controller to a time reference provided by the WWV signal broadcast by the National Bureau of Standards.

Claims

1. In a time controller system of the type which supplies electrical timing pulses of a predetermined pulse rate derived from a frequency source to one or a plurality of clocks for driving the respective clock mechanisms included therein in response to the number of timing pulses received and wherein said system includes means for increasing or decreasing the timing pulse rate relative to said predetermined pulse rate for advancing or retarding the time indication of said clocks, the improvement comprising:

synchronizer circuit means coupled to said system for automatically controlling said means for increasing or decreasing the timing pulse rate following at least one timing pulse measurement period, which period is derived from signals received from a predetermined standard signal source;

radio receiver means coupled to said synchronizer circuit means and being operatively responsive to a WWV signal broadcast by the National Bureau of Standards, said receiver means providing a tone output signal at one minute intervals and wherein said synchronizer circuit means is responsive to said tone output signal and includes circuit means for generating digital signals for defining said pulse measurement period in response to said tone output signals;

said synchronizer circuit means additionally includes means for inhibiting operation of said one or a plurality of clocks until the occurrence of the first said WWV signal following power being applied to the system.

2. In a time controller system of the type which supplies electrical timing pulses of a predetermined pulse rate derived from a frequency source to one or a plurality of clocks for driving the respective clock mechanisms included therein in response to the number of timing pulses received and wherein said system includes means for increasing or decreasing the timing pulse rate relative to said predetermined pulse rate for advancing or retarding the time indication of said clocks, the improvement comprising:

synchronizer circuit means coupled to said system for automatically controlling said means for increasing or decreasing the timing pulse rate following at least one timing pulse measurement period, which period is derived from signals received from a predetermined standard signal souce;

radio receiver means coupled to said synchronizer circuit means and being operatively responsive to a WWV signal broadcast by the National Bureau of Standards, said receiver means providing a tone output signal at one minute intervals and wherein said synchronizer circuit means is responsive to said tone output signal and includes circuit means for generating digital signals for defining said pulse measurement period in response to said tone output signals;

said synchronizer circuit means additionally includes discriminator means for discriminating against false tone signals, said discriminator means providing a signal for rendering operative said synchronizer circuit means after a minimum duration of time upon the occurrence of said tone output signal.

3. The system as defined by claim 2 wherein said WWV signal comprises a 1000 Hz. tone burst and said tone output signal comprises a 1000 Hz. tone.

4. In a time controller system of the type which supplies electrical timing pulses of a predetermined pulse rate derived from a frequency source to one or a plurality of clocks for driving the respective clock mechanisms included therein in response to the number of timing pulses received and wherein said system includes means for increasing or decreasing the timing pulse rate relative to said predetermined pulse rate for advancing or retarding the time indication of said clocks, the improvement comprising:

synchronizer circuit means coupled to said system for automatically controlling said means for increasing or decreasing the timing pulse rate following at least one timing pulse measurement period, which period is derived from signals received from a predetermined standard signal source;

circuit means for receiving periodic signals from said standard signal source and providing periodic output signals in accordance therewith; and

wherein said synchronizer circuit means comprises;

timing pulse counter circuit means coupled to said system timing pulses and providing a count output signal therefrom;

digital circuit means coupled to said receiving circuit means and being adapted to generate a digital pulse coincident with each of said periodic output signals from said receiving circuit means;

decoder circuit means coupled to said counter circuit means and said digital circuit means and being responsive to said digital pulse to decode the count level of said counter circuit means and provide a first control signal for a first count level range and a second control signal for a second count level range;

timer circuit means coupled to said decoder circuit means and being triggered thereby to provide a time control signal which is fed back to said decoder circuit means to inhibit further operation of said decoder circuit means until a subsequent digital pulse from said digital circuit means is generated;

retard circuit means coupled to said decoder circuit means and being responsive to said first control signal to produce a signal coupled back to said means for increasing or decreasing the timing pulse rate and being operative to effect a decrease of the timing pulse rate; and

advance circuit means coupled to said decoder circuit means and being responsive to said second control signal to provide a signal coupled to said means for increasing or decreasing the timing pulse rate and being operative to effect and increase of the timing pulse rate.

5. The system as defined by claim 4 wherein said synchronizer circuit means additionally includes:

time correction inhibit circuit means for inhibiting operation of both said retard circuit means and said advance circuit means in the event said means for increasing or decreasing the timing pulse rate has been manually set into operation.

6. The system as defined by claim 4 wherein said frequency source comprises a crystal oscillator circuit.

7. The system as defined by claim 4 wherein said circuit means for receiving signals from said standard signal source comprises radio receiver means operable to receive WWV broadcast by the National Bureau of Standards and being responsive to the 1000 Hz. tone signal of 0.8 seconds duration broadcast at precise one minute intervals and wherein said periodic output signals therefrom comprises 1000 Hz. tone signals.

8. The system as defined by claim 7 wherein said digital circuit means comprises a tone decoder circuit coupled to said receiver means and being responsive to said 1000 Hz. tone output signals each minute to provide a signal of a first binary digital value during occurrence of said tone signals and of a second binary digital value during the absence of said tone signals.

9. The system as defined by claim 8 wherein said digital circuit means additionally includes a pulsewidth detector circuit coupled to said tone decoder circuit and being operable to provide a digital control pulse to said decoder circuit means in the event that said signal of said first digital binary value is of a predetermined pulse width.

10. The system as defined by claim 9 wherein said digital circuit means additionally includes circuit means defined as a sync latch circuit coupled to said tone decoder circuit for resetting said timing pulse counter circuit and enabling said means for increasing or decreasing the timing pulse rate upon the occurrence of the first 1000 Hz. tone signal following system turn-on.

11. The system as defined by claim 4 wherein said timing pulse counter circuit means comprises a digital counter circuit and additionally including a timing pulse divider circuit coupled to said timing pulses and being operative to divide the timing pulse rate by a predetermined factor to provide a reduced number of timing pulses to said counter circuit.

12. The system as defined by claim 11 wherein said ring counter comprises a decade counter.

13. The system as defined by claim 12 wherein said decoder circuit means includes first circuit means coupled to count outputs 1 through 4 of said decade counter to provide a first intermediate control signal and second circuit means coupled to count outputs 5 through 8 of said decade counter to provide a second intermediate control signal;

a first latch circuit coupled to said first intermediate control signal and a timing signal from said timer circuit means and being operable to generate said first control signal coupled to said retard circuit means;

a second latch circuit coupled to both said first and second intermediate control signal and said timing circuit means for generating said second control signal coupled to said advance circuit means.

14. The system as defined by claim 13 and additionally including a gate circuit coupling said first and second intermediate control signals to said second latch circuit.

15. The system as defined by claim 14 wherein said retard circuit means comprises a digital gate circuit adapted to couple a digital circuit to said means for increasing or decreasing the timing pulse rate for effecting elimination of a predetermined number of timing pulses during the operation period of said timer circuit means.

16. The system as defined by claim 14 wherein said advance circuit means comprises a digital gate circuit for providing a digital signal to said means for increasing or decreasing the timing pulse rate to increase the number of timing pulses applied during the operation period of said timing circuit means.

17. A method of synchronizing time keeping accuracy of a master time controller system to a standard time signal wherein the time controller system drives one or more clocks by means of electrical timing pulses applied thereto from a source comprising the steps of:

sensing the time interval between said standard time signals;

counting the number of said electrical timing pulses during said interval; and

thereafter eliminating a predetermined number of timing pulses for a subsequent second time interval less than said predetermined time interval in the event a first count level is counted and increasing the number of electrical timing pulses for said second time interval in the event a second count level is counted.

18. The method as defined by claim 17 wherein said step of sensing said standard time signal comprises sensing the WWV signal broadcast by the National Bureau of Standards.

19. The method as defined by claim 18 wherein said step of sensing the WWV signal comprises sensing the 1000 Hz. tone burst broadcast at one minute intervals whereupon said timing pulses are counted for one minute intervals in response to sensing said 1000 Hz. tone burst.

20. The method as defined by claim 19 and additionally including the step of generating at least one digital control signal in response to the first said 1000 Hz. tone burst sensed and applying said control signal to said master time controller system for enabling operation of said system.

21. The method as defined by claim 19 wherein said eliminating and increasing step comprising eliminating or increasing the same number of timing pulses at one minute intervals until a count level other than said first and second count level is reached.

22. The method as defined by claim 19 wherein said counting step comprises sub-dividing the number of said electrical timing pulses by a predetermined factor and feeding the sub-divided pulses into a decade counter for said one minute intervals.

23. The method as defined by claim 22 wherein said counting step additionally includes the step of decoding the count level of said decade counter and generating system control signals for eliminating or adding timing pulses in response to the count level decoded.

24. The method as defined by claim 23 wherein said first count level range comprises the counts 1 through 4 of said decade counter and said second count range comprises count 5 through 8.