Repeater (from French word Répéter – to repeat) is a module, that chimes the current time when activated. It is likely the most sophisticated complication in mechanical watches. Nowadays it serves mainly for aesthetical purpose, however at the time when there was no electricity or luminous coating it was the only way for the watches to tell time at night.
It was patented for pocket timepieces by English clockmaker Danial Quare in 1687. Early repeaters produced sounds via tiny bells integrated into the main wheel train. As centuries passed, the bell was left behind and more flat-sounding metal gong took its place. The variety of materials and schemes used in modern repeaters is really impressive. Some repeaters are armed with three or more different tones, while the timepieces are now able to produce full-fledged melodies. Star Caliber 2000 pocket watch by Patek Philippe with Grande Sonnerie module features five gongs and can imitate the 16-note melody of Big Ben of the Palace of Westminster.
Chimes hours with the low tone and the 7.5 minute intervals with the high tone. For instance, if the time is 02:49, the minute repeater will sound 12 low tones and 6 high tones. This kind of repeater is very rare.Quarter repeater
Chimes the number of hours and quarters. If the time is 9:18, the minute repeater will sound 9 hours and one quarter.Five-minute repeater
Chimes the number of hours and five minute periods. If the time is 9:18, the minute repeater will sound 9 hours and 3 five minute periods.Minute repeater
Chimes the number of hours, then number of quarters, and finally the number of minutes. If the time is 11:52, it will sound 11 hours, 3 quarters, and 7 minutes.
There are some hours and half an hour period repeaters around, however they are extremely rare.