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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
Watch
Internally
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 in order 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.)
• 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.
I 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 4312/4313
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 (40 kHz) located in Tamura-gun,
Fukushima Prefecture, and from the Mt. Hagane transmitter (60
kHz) located on the border between Saga Prefecture and
Fukuoka Prefecture.
• The U.S. calibration signal (Call Sign: WWVB) is transmitted by
the National Institute of Standards and technology from Fort
Collins, Colorado.
The time data of the Japanese calibration signal (Call Sign:
JJY) is maintained by the Japan Standard Time Group of the
National Institute of Information and Communications
Technology (NICT). Note that transmission of the standard
wave may be interrupted occasionally due to maintenance,
lightning, etc.
For more information, visit the website of the Japan Standard
Time Group of the National Institute of Information and
Communications Technology (NICT) at the following URL.
http://jjy.nict.go.jp
• Note that the above URL is subject to change.
Time Required for Reception
Signal reception takes anywhere from about two to seven minutes.
In cases where receipt is not possible from the transmitter from
which the signal was last received, reception may take up to 14
minutes.
I To perform signal reception manually
In the Timekeeping Mode,
hold down the D
D
D
D button for
D
about two seconds.
• The watch will beep and
reception will start. 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.
I To interrupt reception
Press the D
D
D
D button.
D
• All other buttons besides D 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 receive indicator on the display also indicates successful
signal reception. The indicator is cleared from the display each
day at midnight.
When reception fails (ERR Indicator)
In the case of an error, the watch will not adjust its current time
setting, but display "ERR" instead.
• 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
This watch is designed to receive the standard time calibration
signal of Japan (JJY) or of the United States (WWVB). The signal
that is received depends on the current Home City setting.
• For information about selecting a Home City, see
"Configuring Home Time Settings". See "World Time City
Code List" for details on city codes.
Home City
Transmitter
Either the Mt. Otakadoya signal
(40 kHz) or the Mt. Hagane signal
(60 kHz)
TYO, SEL, HKG
• Use one of these settings for
reception of the Japanese signal in
Japan or Taiwan.
Fort Collins, Colorado signal
YVR, LAX, YEA, DEN,
• Use one of these settings for
MEX, YWG, CHI, MIA,
reception of the U.S. signal in
YTO, NYC, YHZ, YYT
North America.
• CASIO does not guarantee that the watch will be able to receive a
calibration signal correctly each day.
• 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 Indicator
The receive indicator cycles from
Indicator
"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.
Module 4313
Indicator
Module 4312
Unstable
Stable
Module 4313
• Even under optimum reception conditions, it can take about 10
seconds for reception to stabilize.
• Use the receive indicator 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
Next to a household appliance or
(automobile, train, plane, etc.)
office equipment (TV, speaker, fax,
PC, mobile phone, etc.)
In a location where there is
Near mountains
radio interference
(construction 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.
I To view the last reception date and time
In the Timekeeping Mode, press the D
D
D
D
D button.
• This displays the date and time when signal reception was last
successful, and the current time and date were last adjusted.
• The "
" indicator and the last reception date screen alternate
at two-second intervals.
• 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 Date
Reception Time
Reception Time
2
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