Electronic circuits

The first electronic circuits to be used on a large scale in chronometry comprised triodes or other electronic tubes. The first tuning fork and quartz electronic oscillators were made around 1920. Electronics engineers had detected the annual variations in the speed of the earth's rotation as early as 1934 by means of their quartz watches, yet it took until 1951 for these variations to be accepted by astronomers! Little by little, quartz clocks replaced the mechanical timekeepers maintained at constant pressure and temperature in observatories. The atomic clock has just as easily replaced quartz clocks as the Earth's standard for measuring time. Indeed, the atomic clock is an absolute time and frequency standard; it is not affected by ageing and is independent of pressure, temperature and stress. Let us not forget that an atomic clock is a quartz clock whose frequency is periodically adjusted to that of the atomic beam resonator.