Minute repeater

A minute repeater sounds the time on demand, in stages. The British Museum's record for a watch by Thomas Mudge of London, dated 1755 (museum number 1984,0301.1), describes a gilded-brass movement with "separate trains for the quarter-striking and pendant-operated minute repeat mechanisms, both sounding on a bell". The museum's curatorial comments explain that the repeating work is operated "on demand to the nearest minute, simply by pushing in the watch pendant to activate the mechanism", and that when activated it "would strike a bell to sound the hour, the quarters past the hour and the minutes past the quarter".

That is what separates a repeater from a striking clock or clock-watch, which sounds the hours whether or not anyone asks. The British Museum's record for a watch by Sir John Bennett of 1878–1880 (museum number 1980,0515.1) describes the object as a "Minute-repeating, grande-sonnerie clock-watch" — a single watch that does both — and notes of the two functions that "the striking function must be completed before the watch can be made to repeat". Automatic striking runs on its own; repeating happens only when a case control is pressed.

Both functions draw on stored energy rather than on the going train alone. The same British Museum record describes Hector Golay's arrangement in the Bennett watch, in which "a single mainspring is used to power both the quarter- and hour-striking functions". Neither record gives a figure for how much running time the striking work consumes, so no power-reserve cost is stated here.