How A Radio-Controlled Watch Works; Reception Ranges - Casio 2891 Operation Manual

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How a Radio-controlled Watch Works

What is a radio-controlled watch?
Your radio-controlled watch is designed to receive a time
calibration signal that contains standard time data, and adjust its
current time setting accordingly.
Signal is received by
built-in antenna.
Transmitter
Long-wave time
calibration signal
Watch decodes
received data and
Signal data
converts it to time
data.
Decode
Time data
Time is adjusted
Cesium
according to time
atomic clock
Internally
Watch
data.
After the watch receives the Standard Time signal, it performs
internal calculations to determine the current time. Because of
this, there may be an error of up to one second in the
displayed time.
Receiving the Calibration Signal
There are two methods you can use to receive the time calibration signal.
• Auto receive (Reception is performed automatically at
midnight, 1:00, 2:00, 3:00, and 4:00 each morning.)
• Manual receive (You initiate reception using a button operation.)
• Once auto receive is successful on a particular day, the auto receive
operation for subsequent times are not performed for that day.
• If reception is not successful for any of the normal auto receive operations
shown above, auto receive is performed one more time at 5:00 a.m.
• The watch is set up for auto receive at the factory, so all you need to
do is to place it in a location that allows good reception each night.
❚ To position the watch for optimum reception
Remove the watch from your wrist and place it somewhere so its top
(12 o'clock, where the antenna is located) is facing approximately in
the direction of the signal transmitter. Keep it away from metal objects.
Resin Band
Metal Band
• Orienting the watch so it is sideways to the transmitter makes it
more difficult to receive the signal.
• Do not move the watch while it is receiving the calibration signal.
Operation Guide 2891
Calibration Signal
• The Japanese calibration signal (Call Sign: JJY) is maintained by
the National Institute of Information and Communications
Technology (NICT). It is transmitted 24 hours a day from the Mt.
Otakadoya transmitter (40kHz) located in Tamura-gun, Fukushima
Prefecture, and from the Mt. Hagane transmitter (60kHz) located
on the border between Saga Prefecture and Fukuoka Prefecture.
Though the calibration signal normally is transmitted 24 hours
a day, transmission may be interrupted occasionally due to
maintenance, lightning, etc.
Time Required for Reception
Signal reception takes anywhere from about two to seven minutes.
• Under certain conditions, signal reception can take as long as 14 minutes.
• See "Configuring Auto Receive Settings" for more
information about auto receive.
❚ To perform manual receive
1.
In the Timekeeping Mode, press the D
D
D
D button six
D
times to enter the Receive Mode.
2.
Hold down the C
C button
C
C
C
for about two seconds.
• The watch will beep and
reception will start. The display
will flash and the receive icon
(
) will start to cycle through
(2 seconds)
its numbers.
❚ To interrupt reception
Press the C
C button.
C
C
C
• All other buttons besides C are disabled during signal reception.
When reception is successful
The watch terminates reception and adjusts the current time. Next it
beeps and then displays the date and time the adjustment was performed.
• The "
" icon (with all numbered segments visible) on the display
also indicates successful signal reception.
When reception fails
The watch does not adjust its current time setting and displays
"ERR" when signal reception is unsuccessful for some reason.
• The display will return to the normal timekeeping screen automatically
if you do not perform any operation for about one or two minutes.

Reception Ranges

With this setting, the watch automatically selects either the Mt.
Otakadoya signal (40kHz) or the Mt. Hagane signal (60kHz),
whichever is strongest.
1000km
Transmitter Location
Mt. Otakadoya
(40kHz)
500km
500km
Mt. Hagane
(60kHz)
1000km
• Under optimum conditions, the calibration signal should be
receivable up to 1,000 kilometers from the transmitter. Note
that the wave is relatively weak at distances greater than
500km, so reception may be poor at long distances.
• Geographic contours, nearby buildings, the season, the time of
day, can even make reception impossible even when you are
within range of the transmitter.
• Best reception is possible late at night.
Receive Icon
Receive Icon
The receive indicator cycles from
"Unstable" through "Stable" as
shown below while reception is in
progress. How far it cycles depends
on the signal strength.
Keep the watch in a location where
reception is stable while reception is
in progress.
Unstable
Stable
• Even under optimum reception conditions, it can take about 10
seconds for reception to stabilize.
• Use the receive icon to check reception status and to
determine the best location for signal reception.
• Note that weather, the time of day, surroundings, and other
factors can all affect reception.
Location
Reception is difficult and may even be impossible in the locations
described below. Avoid such locations when performing signal
reception.
• You should think of your watch operating like a radio or TV when it
is receiving the calibration signal.
Among or near buildings
Near high-voltage lines
Inside a vehicle (automobile,
Next to a household appliance or
train, plane, etc.)
office equipment (TV, speaker,
fax, computer, cell phone, etc.)
In a location where there is
radio interference (construction
Near mountains
site, airport, etc.)
If you are experiencing problems with reception, move away
from the types of locations described above to a location with
better reception, and try again.
❚ To view the last reception date and time
In the Timekeeping Mode, press the D
D button six times to
D
D
D
enter the Receive Mode.
• This displays the date and time when signal reception was last suc-
cessful, and the current time and date were last adjusted.
• To return to the Timekeeping Mode, press the D button again.
• The display will return to the normal timekeeping screen
automatically if you do not perform any operation for about one or
two minutes.
Reception Time
(6 times)
Reception Date
5

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