Frequency standards

On the occasion of the 90th anniversary of the birth of Prof. Jamusz Groszkowski, who died in 1984, and who published a monograph on the generation and stabilization of frequency, the article reviews the technical progress in this field in the course of the last three decades. The parameters defining the quality of frequency standards are called, the concepts of reproducibility and short-term frequency stability are explained. The present status of the frequency standard technology is surveyed. The quartz frequency standards and quantum frequency standards are described. Methods of determining short-term stability of frequency standards are presented in an appendix.