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The clocks in the above sections are one
of the following three technologies. Each has its own implications
toward accuracy.
Quartz: Quartz alarm clocks,
like any quartz clock, has it's accuracy controlled by a quartz
crystal. A precisely trimmed quartz crystal is used to generate an
electrical timing signal that regulates the speed of the clock.
Quartz clocks may gain or lose around one second per day, and the drift
rate may depend somewhat upon temperature.
Auto setting: Auto-setting
clocks are a relatively new technology. They are available under a
number of names, depending on the manufacturer. Auto-setting clocks
are built with a quartz crystal to regulate speed, and a built in
integrated circuit that knows the approximate time, and the date.
Although they can gain or lose time like any quartz clock, they have one
advantage. They know about, and will automatically adjust for
daylight savings time.
Atomic, or Radio Controlled:
The United States Government National Institute of Standards and
Technology maintains a radio station, WWVB, in Ft. Collins,
Colorado. This radio station transmits highly accurate time
information. Atomic, or Radio Controlled clocks receive this signal
when they can, and set themselves. These will maintain time accurate
to a fraction of a second as long as they are placed in a location where
they can receive the signal. Like any radio receiver however, they
may not be able to receive the signal if they are in a building with a lot
of steel in the structure, near computers or cordless phones that may
generate interference, or if the weather is unsuitable. Please note.
The signal they receive does not propagate well during the
day. That's the nature of the signal, not the clock. These
clocks are designed to catch the signal when they can, generally in the
middle of the night, calibrate themselves, and then run quite accurately
for days until they can catch another signal. When
you first put in the batteries, they will most likely not set themselves
until the middle of the night. The analog clocks generally tick for
a few seconds, advance to 4:00, and wait. The digitals display
various things while they wait. That's normal. By morning,
weather permitting, it
should be correct.
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