MEASURING DISTANCE
A tachymeter-equipped watch can be used to measure distance by timing the travel over the
distance while the speed is held constant. The tachymeter scale is rotated to align with the second
hand at the start of the length to be measured. When the second hand reaches the point on the
scale where the speed indicated equals the speed of the vehicle, one unit of distance (miles if
speed is miles per hour, kilometres if kilometres per hour, etc.) has been covered. For example, if
you travel at a constant 80 mph (or at 80 km/h), then the distance travelled while the second hand
sweeps to “80” (45 seconds) will be exactly 1 mile (or 1 kilometre at 80 km/h).
ROTATING SCALE
Some tachymeter scales are on a rotating, indexed bezel. This allows two additional modes of use:
The tachymeter bezel can be aligned with a free running second hand, and, more subtly, can be
used to find the average speed over longer times/distances. Set the rotary bezel index to the po-
sition of the minute hand, note the current mileage/distance. Glance at the position of the minute
hand on the tachymeter scale 60 units of distance later, and average speed will be indicated. A
little mental math allows interim averages, easiest at 1/4 (15 unit) and other integer values. Alter-
natively, instead of using minute hand, align index bezel to the second hand and observe passing
one unit of distance when position of the second hand will then indicate average speed.
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The deployment buckle is opened by pulling the joined ends of the buckle out-
ward, away from each other, like a butterfly spreading its wings. The deployment
buckle can then be fastened around the wrist.
To adjust for the size of your wrist, there is a hinged clasp must be pulled open,
away from the edge at the end of the watch, to expose the pin which fits into the
holes on the band.
Slide the band through the now open hinged clasp. Once you find the proper
hole on the watch band and push the pin through the hole, you press the top and
bottom portions of the hinged clasp back together. The hinged clasp will snap
firmly into place.
DEPLOYMENT BUCKLE
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Содержание ISA 9238 1970
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