Clocks in synchrony

In 1837, Samuel Morse presented a telegraph which transformed text into electric signals. This is also possible with time specifications: As early as in 1840, Carl August Steinheil, in Munich, and Alexander Bain, in Scotland, sent the precise clock time to different places via electrical lines.

Up to that point, it had been impossible to make all clocks in a town or even in one single building mark the same time. Now, one “master clock” controlled a large number of “slave clocks”, most of which only featured a motion train to move the hands by electric impulses from the master clock.

In the twentieth century, these clock systems were constantly refined. The master clocks adjusted themselves, even after a blackout. There was often also an auxiliary master clock, so the clock system could keep the correct time even if the first master clock failed.

However, the maintenance of these systems was expensive. From 1973 on, it was possible to receive the exact time through a wireless system. The slave clocks were increasingly replaced by autonomous radio-controlled clocks and the master clocks became superfluous.