The Fedchenko regulator plays an important role in the history of the precision pendulum clock. It is the last type of pendulum clock to be used practically as a time standard. Developed in the Soviet Union it saw continued use throughout the latter half of the 20th century in Soviet observatories, broadcasting centres and transport networks. Its simple robust design and accuracy of around 1 millisecond per day led to its continued use, despite the existence of quartz and atomic timekeepers.


The clock movement is assembled within a steel vacuum chamber with sealed glass domes to both top and bottom. Visible through the uppermost dome is the arched, numbered and dated pendulum support. The isochronous suspension was designed by Feodosii Fedchenko circa 1952 and consists of three one-piece springs. The central spring is slightly longer than the outer two, and as the pendulum swings away from its rest point the shorter springs act upon the pendulum and in doing so corrects circular error. The pendulum rod is made from invar, which has a negligible expansion coefficient, the copper pendulum bob is suspended from its centre of mass and so any expansion or contraction caused by changes in temperature will not affect the timekeeping. The pendulum is fitted with permanent magnet, which passes through a coil, receiving electro-magnetic impulse as it passes through its point of rest. In order to prevent temperature changes affecting the positioning of the coil, relative to the pendulum’s permanent magnet, it is mounted to an invar rod that matches the pendulum rod. This rod is fixed to the back of the pendulum support at the same height as the top of the pendulum. The clock sends electrical pulses to the slave dial every second. The contact is made mechanically via a sprung rod, which is mounted on the suspension block.