An early domestic mains electric clock, using a 'synchronous motor', in a wooden free-standing case. Dial inscribed 'Warren Synclock / Everett Edgcumbe / London'.

The first clocks using alternating current (AC) electricity as their time source were patented by the American inventor Henry Warren in 1918. They took their time from the domestic mains electricity supply. Power stations used accurate clocks to monitor and correct the frequency of the alternating current they generated, making it sufficiently precise to regulate the clock's movement.

The first British models of these 'synchronous' clocks were introduced by Everett Edgcumbe in the late 1920s and marketed as the 'Warren Synclock'. This is a very early example.

From the 1930s to the 1960s, synchronous clocks were very popular, providing accurate time at low cost. They never needed winding, and every clock in the house read the same time. Many new houses had electric sockets positioned near the mantelpiece to allow easy connections for these clocks.

Synchronous motor electric clocks take their time from the domestic mains electricity supply. Power stations used Greenwich Time to monitor and correct the frequency of the alternating current they generated, making it sufficiently precise to regulate the clock's movement. The first synchronous motor clocks were patented by the American inventor, Henry Warren, in 1918. The first British models were introduced by Everett Edgcumbe in the late 1920s and marketed as the 'Warren Synclock'. This is a very early example.