PURPOSE: To obtain a time standard with less variation of frequency with temperature by driving the tuning fork type crystal oscillator by means of the secondary harmonic.

CONSTITUTION: Arms 19a, 19b of the tuning fork type crystal oscillator are bent outwards at the base and inwards at the tip simultaneously, and are done in the opposite way next. These continuous beniding motions produce the oscillation. Two electrodes 21a, 21c are placed on both edges of the tip side 20a-1 of the arm 20a, another one 21b is put on the central part. Also two other electrodes 21d, 21f are placed on both edges of the base side 20a-2 and another one 21e is put on the central part. The electrodes 21a, 21c, 21e are connected with each other, others 21b, 21d, 21f are done, and these are reverse in polarity with respect to the direction of X- axis. Similarly the arm 20b is also provided with the electrodes. As a result, the oscillator 20 are driven by the secondary harmonic.