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Overall diameter of the WT-3181P is a full 18 inches (457.2 mm),
and its face is 13.75 inches (349.3 mm) in diameter. The big, bold
hour numerals are 1-3/16 inches (30.2 mm) tall for easy viewing
from a distance. The analog thermometer has dual concentric
temperature scales. One reads from -40°
to +130°F, and the other
reads from -35°
to +55°C. The analog
hygrometer indicates relative humidity from 0 to 100 percent. The
clock's lens is glass for easy cleaning without scratching, and
it's sealed with a rubber gasket to protect the face and hands
from moisture.
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Radio-Controlled Time:
The NIST (National Institute of
Standards and Technology, Time and Frequency Division) maintains a
radio station, WWVB, in Ft. Collins, Colorado. The WWVB radio
station derives its signal from the NIST atomic clock in Boulder,
Colorado. A team of atomic physicists is continually measuring
every second of every day, to an accuracy of ten billionths of a
second per day. These physicists have created an international
standard, measuring a second as 9,192,631,770 vibrations of a
Cesium-133 atom in a vacuum.
WWVB (the station’s
identification just like any other radio station) continuously
broadcasts time and frequency signals at 60 kHz. The carrier
frequency provides a stable frequency reference traceable to the
national standard. There are no voice announcements on the
station, but a time code is synchronized with the 60 kHz carrier
and is broadcast continuously at a rate of 1 bit per second using
pulse width modulation. The time code contains the year, day of
year, hour, minute, second, and flags that indicate the status of
Daylight Saving Time, leap years, and leap seconds.
The LaCrosse Technology WT-3181P
Atomic Wall Clock:
The La Crosse Technology WT-3181P
Atomic Wall Clock maintains its incredible accuracy by
automatically tuning into the WWVB radio signal. The built-in
antenna ensures reliable signal reception up to 2000 miles
(3200km) from the WWVB transmitter. As a result, the La Crosse
Technology clock will calibrate to the atomic clock not only
throughout the mainland U.S. but also in much of Canada. You need
only insert the battery, press the appropriate time zone button,
and wait until the signal is received (overnight). In all other
locations worldwide, the LaCrosse clock can be manually set and
will provide the high degree of accuracy of any quality quartz
clock.
In a nutshell, here's how the the
LaCrosse clock works: The clock's antenna is specifically tuned
for optimal reception of the 60 kHz time signal. The time signal
received on the antenna is demodulated by an onboard receiver,
which sends the information to the clock's CMOS microprocessor for
decoding. Once your clock has automatically set its time for the
first time, it ensures continuing accuracy by automatically tuning
into the WWVB radio signal once per day after midnight. As long as
your clock is kept within transmitter range, it will continue to
display the absolutely precise time, even automatically adjusting
for summer time/winter time changeovers. Should you move your
clock out of transmitter range for an extended period of time, the
clock will continue to operate as a highly accurate
quartz-controlled clock. Upon re-entering the transmitter range,
your clock will correct itself again to the precise WWVB time
signal.
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