Phase stable quartz crystal units

A report of the analytical and experimental studies of crystallographic orientations and crystal plate mountings leading to an improved phase stable crystal unit under mechanical shock and vibration is made. An hypothesis will be advanced which suggests that a neutral axis (or axes) exists in thep lane of an AT plate and if the blank is mounted at the ends of this axis (or axes), the frequency (or phase) of the crystal unit will not be changed by any stress applied through the mounting points. Evidence will be given showing the importance of oscillator design on the problem of phase (or frequency) stability as a result of mechanical shock and vibration.