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The WT-5720 atomic projection clock is
black and silver in color. Its LCD display shows time of
day/date (selectable),
time zone, and indoor temperature. The time is also projected in
large numbers (3 inches tall at 6 feet) on the wall or ceiling.
This clock has dual alarm settings with adjustable snooze. Designed for
table or shelf placement, the clock can be powered from the included ac
adapter or optionally from two AA batteries for use when
traveling.
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The La Crosse WT-5720
Radio Controlled Atomic Projection Clock:
The La Crosse Atomic Projection Alarm 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 atomic 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 batteries, wait until the signal is received,
and program the desired additional settings. In locations
outside of WWVB range, the LaCrosse atomic 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
La Crosse atomic 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 atomic 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
at midnight. As long as your clock is kept within
transmitter range, it will continue to display
the absolutely precise time, automatically adjusting for summer time/winter time
changeovers if the daylight savings time option is ON. Should you
move your atomic clock out of transmitter range for an extended period
of time, the atomic 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.
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.
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