La Crosse Technology WS-3610 - Manual (Page 15)

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corresponding *LO AL* and *HI AL* fields; the individual values
are displayed in the same manner as individual Min/Max values.
(See above)
At any time the opposite respective menu (MIN/MAX or ALARM)
can be accessed via its corresponding field.
Touching the *EXIT* field at any time will return the LCD to its
normal display.
6 Radio Controlled WWVB Signal Reception and Clock
The NIST (National Institute of Standards and Technology—
Time and Frequency Division) WWVB radio station is located in
Ft. Collins, Colorado. A tower located there transmits the exact
time and date signal continuously throughout the United States
at 60 kHz. The signal can be received up to 2,000 miles away
through the internal antenna in the Base Station.
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. For
more information on the atomic clock and WWVB please see the
NIST website at
http://www.boulder.nist.gov/timefreq/stations/wwvb.htm .