Telegraphy – Systems – Line-clearing and circuit maintenance
Patent
1975-07-14
1977-01-25
Curtis, Marshall M.
Telegraphy
Systems
Line-clearing and circuit maintenance
343225, H04L 700
Patent
active
040052664
ABSTRACT:
A plurality of widely separated local time base systems are synchronized with a master time base system by means of digitally encoded radio signals. All of the time base systems comprise oscillator driven digital clocks which produce a cyclically recurring series of sequential time slots which are individually assigned to the master and local systems to provide time division multiple access to the master system from each local system. Coarse time synchronization is obtained by the transmission of a coarse synchronization signal from the master to each local system at the beginning of the series of slots in the master's time base which resets all local time bases to the beginning of the series of slots. Fine synchronization is made during the individual time slot assigned to each local system by the transmission of fine synchronization request and fine synchronization reply signals which are utilized to produce a synchronization error signal in each local system. The error signal is employed to generate frequency and phase corrections for the local oscillator and time corrections for the local clock in accordance with a programmed control state sequence in which the oscillator and clock correction gains used for a particular correction are determined by the number of system cycles between fine corrections and the magnitude of the error. A digital filter technique is utilized which approximates the operation of a simple Kalman filter.
REFERENCES:
patent: 3128465 (1964-04-01), Brilliant
patent: 3851101 (1974-11-01), En et al.
patent: 3936604 (1976-02-01), Pommerining
Blauth Gary William
Coralnick Philmore
Lehr Stanley
Curtis Marshall M.
Kennedy Thomas W.
The Singer Company
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