I .
P R I N C I P A L W A T C H F U N C T I O N S A N D C O M P L I C A T I O N S
POWER RESERVE
A hand indicates how much of the watch's power supply
remains (for both self-winding and hand-wound watches).
DUAL TIME FUNCTION
A watch equipped with a dual time complication is able to
indicate a "2nd time zone". This second time can be read on
a central hand or a hand located in a dial graduated from
1 to 24.
In practice, the main hour hand is typically set to the local
time of where one is during one's travels, and the time of
the second time zone can specify the time where one lives,
for example.
CHRONOGRAPH
A chronograph is a watch which can measure a period of
elapsed time. A chronograph model generally also contains
a central seconds-hand for counting seconds, a counter for
totaling minutes and another for totaling hours.
FLYBACK
The flyback function means exactly what it says, to "fly
backward" : it allows the wearer to move from one chro-
nograph reading to another in a single button push instead
of three.
TACHYMETER
Scale used to measure average speed in km/h based on the
time needed to traverse 1000 m.
For example, to measure your average speed while driving,
start the chronograph at a roadside mile marker, then stop
it exactly 1 km farther on (next mile marker). The seconds-
hand uses the tachymeter scale to indicate your average
speed in km/h for the kilometer you just traveled.
TELEMETER
Scale used to measure the distance separating an observer
from a phenomenon which is first visible and then audible. Its
graduation is based on the speed of sound (343 m/s).
For example, to determine a storm's distance from the wear-
er, start the chronograph at the first appearance of lightning ;
then stop it when the thunder can be heard.
Look at the dial of your watch, the seconds-hand uses the
"telemetric scale" to indicate the distance separating you
from the place where the lightning occurred.
MOON PHASE
Watches with a moon-phase complication display the cycles
of the moon on their dial (first quarter, full moon...). Moon
phases are generally displayed using a moving disk which
makes one rotation every lunar month (29 and one half day).
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