Jordan and Hamburg
Electronic timepiece
 An electronic timepiece is provided with a timebase signal source comprising a relatively low frequency quartz crystal oscillator circuit and with means for compensating the timebase signal frequency for the effects of temperature changes on the low frequency oscillator circuit, and further with means for comparing the timebase signal frequency with the frequency of a relatively high frequency quartz crystal oscillator circuit having high stability against aging changes, to thereby compensate for changes in the timebase frequency caused by aging of the low frequency quartz crystal vibrator, this comparison being carried out only within a specific narrow range of operating temperatures. 
Citizen Watch Company Limited
G H
G04F H03L
inventional inventional
Makoto Shinichi Fuminori
Yoshida Watanabe Suzuki