BREIL OS11 Mode D'emploi page 13

TACHYMETER*
F
The Tachymeter is used to measure the speed of a vehicle. By knowing how many
seconds the vehicle to travel one kilometre, the tachymeter can measure the
approximate average speed in km/h during a journey (over a maxinum measurable time
of 60 seconds).
If the chronograph is started at the same time as the start of the distance measurement,
and stopped after 1km, the average speed can be calculated from the position of the
second hand. If the vehicle covers the distance one km in 45 seconds, the approximate
average speed is 80 km/h.
TELEMETER*
The Telemeter is a distance indicator which allows distance to be calculated on the
basis of the speed of sound. It is useful, therefore, for aviation, navy, army and artillery
purposes. It can also measure how far away a thunderstorm is.
The hand is started the second a flash, smoke or lightning is seen and stopped when
the actual sound is heard. The distance, from 1 to 20 kilometres, between the observer
and the explosion or storm is read from the telemetry scale.
* Not available on all models
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