English Specificsection
22
TELEMETERFUNCTIONThetelemeter scale measures the distance of a
phenomenonwhich is first visible and then audi-
ble. The chronograph hand is released at the
instant the phenomenon is seen and stopped
when the sound is heard. Its position on the
scalesho ws,at a glance, the distance, in kilo-
meters, separating the phenomenon from the
observer.
The telemeter is so graduated that the sound
travels at a speed of 330.7 meters (approx.
1084.97 feet) / second, that is 1 km (approx.
0.62137miles) in 3 seconds.
Ifwe want to know at which distance a thunder
stormis taking place, for example, the chrono-
graphhand is activated as soon as the flash of
lighteningis visible. When the crash of thunder
isaudible, the chronograph hand is stopped.The
hand indicates on the telemeter scale the
distance between the observer and where the
phenomenonhas taken place.