Timing systems which are driven by unadjusted quartz crystal oscillators accumulate errors due to oscillator frequency instability. .To realize maximum timekeeping precision, assuming a frequency calibration is available intermittently, the oscillator frequency must be c or r e spondingly readjusted or the clock must be reset , or a bookkeeping method employed to systematically account for errors. At best, none of these procedures is as satisfactory as having a stable frequency available continuously; besides being time consuming, the above expedients always introduce a possibility for err 'or. In an operational system, the problem is compounded because coordination is required among a number of people in a number of stations. To minimize these disadvantages and in some cases improve accuracy, a method of operation which retains oscillator synchronization as automatically as possible is desired,.