1. Electronic oscillators

The history of time measurement goes back to ancient times. Its origins can be traced back to astronomy. Mechanical clocks flourished from the 16th century onwards, reaching their golden age in the 18th century. The first patent for electrical maintenance of a pendulum was taken out in 1840. The first piezoelectric oscillator was developed by Cady in 1918, from which came the quartz clock, the first practical and commercial form of which was Marrison's Crystal Clock (1930) [1].

However, despite this technological acceleration, the second fundamental unit of time measurement in the International System (SI) remained based on astronomical observations until the second half of the 20th century. The second was first defined as a fraction of the duration of one rotation of the Earth around its axis, then as a fraction of the terrestrial...