The crystal resonator- a digital transducer

Precision piezoelectric quartz resonators have evolved during a half century of research, development, and engineering. It is an evolution that started with rudimentary concepts and a precision of one part in a thousand, and emerged today with a precision of a few parts in 1012. Although there have been significant steps forward through single contributions, the evolution has been a continuous improvement with an order of magnitude achieved every five to seven years. Not that anyone was particularly aware of these milestones, but, viewed in total, this improvement of a billion to one must stand as one of the truly amazing developments of this electronic age.