Shortt-Synchronome clock

Shortt-Synchronome clock, a free pendulum clock, patented in 1921.

An early mechanical version of a phase-locked loop was used in 1921 in the Shortt-Synchronome clock.

The Synchronome company manufactured electrically operated master clocks, patented in 1907, such as the Shortt-Synchronome clock.

In the 20th century, W.H. Shortt invented a free pendulum clock / Shortt-Synchronome clock with an accuracy of one-hundredth of a second per day.

In 1921 William H Shortt invented the Shortt-Synchronome clock, the most accurate commercially produced pendulum clock; it was the first clock capable of measuring variations in the Earth's rotation.

Gascoigne reestablished the Time Service at Mount Stromlo, using two Shortt-Synchronome clocks and astronomical observing equipment that he and his colleagues adapted; the Time Service remained at Mount Stromlo until 1968.