Casio 3731 Operation Manual Download Page 3

Operation Guide 3731

3

To specify the illumination duration

1.

In the Timekeeping Mode,
hold down the 

A

A

A

A

A

 button

for about two seconds.

This will cause the currently
selected time zone to flash on
the display, and the second
hand to move to 12 o’clock.

2.

Press the 

C

C

C

C

C

 button three

times to display the
flashing seconds count.

3.

Press the 

B

B

B

B

B

 button to

toggle the illumination
duration between about 2
seconds (

 indicator) and

1.5 seconds (no indicator).

 indicator 

(Appears only on 
the setting screen.)

4.

After the setting is the way you want, press the 

A

A

A

A

A

button to exit the setting screen.

The second hand will move to the current time as kept
internally, and resume normal movement from there.

The watch will also exit the setting screen automatically if you
do not perform any operation for about two or three minutes.

Time Zone

Seconds

(3 times)

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 data

Transmitter

Internally

Decode

Watch

Time data

Long-wave 
time 
calibration 
signal

Cesium 

atomic clock

Signal is received 
using built-in antenna.

Watch decodes 
received data 
and converts it 
to time data.

Time is adjusted 
according to 
time 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.

Calibration Signal

The Japanese calibration signal (Call Sign: JJY) is maintained by
the National Institute of Information and Communications
Technology (NICT). It is a long wave signal 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.

Note that transmission of the time calibration signal may be
interrupted occasionally due to maintenance, lightning, etc.

How a Radio-controlled Watch Works

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.

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.

Near high-voltage lines

Among or near buildings

Near mountains

Inside a vehicle

 (automobile, train, plane, etc.)

In a location where there is
radio interference (construction
site, airport, etc.)

Next to a household
appliance or office equipment
(TV, speaker, fax, computer,
cell phone, etc.)

Reception Range

This watch can be configured to select the strongest Japanese
signal (40kHz Mt. Otakadoya signal or 60kHz Mt. Hagane signal),
and use that one for calibration. is stronger.

1000km

Mt. Hagane
(60kHz)

Mt. Otakadoya
(40kHz)

500km

1000km

500km

Japan Transmitter 
Locations

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, seasonal conditions, 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.

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 

B

B

B

B

B

 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.

To position the watch for optimum reception

Remove the watch from your wrist and place it somewhere so its
top (12 o’clock side, where the antenna is located) is facing
approximately in the direction of the signal transmitter. Keep the
watch 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.

Time Required for Reception

A calibration signal receive operation takes anywhere from about
two to seven minutes.

Note that when “A” (Auto Select) is specified as the transmitter
selection mode, signal reception can take up to 14 minutes.

See “Configuring Auto Receive Settings” for more information.

To perform manual receive

In the Timekeeping Mode, hold
down the 

B

B

B

B

B

 button for about

two seconds.

The watch will beep and reception
will start. The receive (

) indicator

will appear on the display to indicate
reception conditions.

To interrupt reception

Press the 

B

B

B

B

B

 button.

All other buttons besides 

B

 are disabled during signal reception.

When reception is successful
The watch will terminate reception and adjust the current time.
Next it will beep and then display the date and time that the
adjustment was performed.

The receive indicator (

) will remain on the display to indicate

that reception was successful.

The second hand will move to the correct position in accordance
with the digital time, and resume normal movement from there.

Reception Error
The will display “

” without adjusting the time setting when

signal reception is unsuccessful for some reason.

The watch will return to the Timekeeping Mode screen automatically
if you do not perform any operation for about one or two minutes.

Summary of Contents for 3731

Page 1: ...Hands move to 12 o clock Moves to current level Returns to current seconds position Time in Current Time Zone Time Zone TIME DIFFERENCE Alarm Number Alarm Time How the sleep state works Display sleep state The display sleep state is triggered whenever the watch is left in the dark for three or four days The display goes blank in the display sleep state Alarms and the hourly time signal continue to...

Page 2: ...the face of the watch Pressing the D button illuminates the face regardless of whether the auto light switch is on or off You can use the procedure under To specify the illumination duration to configure the illumination duration as approximately 1 5 seconds or 2 seconds You may hear a faint rattling sound when you move the watch around This sound is caused by the movement of a metal bulb that con...

Page 3: ...onfigured to select the strongest Japanese signal 40kHz Mt Otakadoya signal or 60kHz Mt Hagane signal and use that one for calibration is stronger 1000km Mt Hagane 60kHz Mt Otakadoya 40kHz 500km 1000km 500km Japan Transmitter Locations 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 ...

Page 4: ...s will cause the watch to beep and then exit the receive operation Make sure you are within the range of the calibration signal transmitter before performing the reception operation Remember that geographic contours nearby buildings seasonal conditions the time of day can even make reception impossible even when you are within range of the transmitter Proper reception may be impossible if there is...

Page 5: ...ute setting flashes Hour Forward Back Minute 5 Use the D D D D D and B B B B B buttons to change the minute setting Holding down either button scrolls the setting at high speed 6 When the setting is the way you want press the A A A A A button This exits the setting screen An alarm is turned on automatically whenever you change its settings The display also will exit the setting screen automaticall...

Page 6: ...ime Though the digital time freezes the stopwatch hands continue to move This stops the elapsed time operation Pressing the A button while timing is stopped resets the stopwatch Resetting the stopwatch stores the final elapsed time that is on the display to lap split time memory Start Lap Number Lap Lap Time Reset Stop Start Split Split Time Reset Stop Lap Time Display Split Time Display Elapsed T...

Page 7: ...ing the A button in the Dual Time Mode displays the time differential of the currently selected time zone for about one second Time Zone Time in selected time zone Forward Using Summer Time DST Summer time or Daylight Saving Time DST as it is called in some countries calls for setting clocks ahead one hour during the summer season Note that the use of summer time depends on the country and even th...

Page 8: ... D D D D D button to reset them to 00 in accordance with the time signal on the radio TV etc Pressing the D button while the seconds count is in the range of 30 to 59 resets it to 00 and also adds 1 to the minutes Pressing the D button in the range of 00 to 29 resets the seconds count without changing the minutes 9 While the hour minutes year month or day setting is flashing use the D D D D D butt...

Page 9: ...il it completes a 12 hour cycle or until you press any button to stop it 6 Press the A A A A A button to select the stopwatch 1 20 second hand for adjustment 24 hour hand Minute Hand Hour Hand Forward Back 7 If the 1 20 second hand is not aligned with the 12 o clock position use the D D D D D button to adjust it Each press of the D button advances the 1 20 second hand by one step Holding down the ...

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