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.