Image Number 3 for United States Patent #4503353.
Axes X', Y' and Z' of a resonator are established from the axes X, Y and Z of a quartz crystal by virtue of two rotational movements through angles .phi. and .theta., respectively. The resonator is energized to vibrate in accordance with the fundamental torsional mode. The angles of cut .phi. and .theta. are such that the first-order temperature coefficient is zero. The torsional mode may be coupled to a flexural mode in order to render the second-order temperature coefficient zero. The fork tines extend in the X' direction. In other embodiments the tines extend in the Y' direction and the rotation .phi. and .theta. are about the X and Z' axes, respectively.