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Casio 3721 User Manual

Casio 3721
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Operation Guide 3721
1
MA0410-EA
Each press of the
BB
BB
B button sounds a confirmation tone and cycles through available modes in the sequence shown below.
The watch will revert to the Timekeeping Mode automatically if you leave it in any other mode without performing any operation for about two
or three minutes.
(Mode Change)
(Light)
Minute Hand
Second H
and
Hour Hand
Date
Timekeeping Mode
If the time setting is not correct...
Normally, you should never need to adjust the time setting of the watch as long as it is
able to receive a time calibration signal. If signal reception is impossible for some reason,
use the procedures under “Adjusting the Home Positions” to check the home positions of
the hands, and make adjustments as required.
Button
Button
Receive
Successful
OFF
ON
Receive Failed
Use this mode to adjust
the home positions of
the analog hands.
The home positions of the
hands are correct when
they point to 12 o’clock.
Use this mode to set the alarm time and to turn
the alarm on or off.
The second hand will move to either “ON” or “OFF”.
Use this mode to check if
signal reception is being
performed normally.
The second hand will move
to either “GET” or “NG”.
Receive Result Mode
Alarm Mode
Home Position Adjustment Mode
Modes and Hand Movement
Charging Precautions
Avoid charging the watch in the following locations, and anywhere
else where the watch may become very hot.
On the dashboard of an automobile parked in the sun
Very close to an incandescent light source or other sources of
heat
In a location exposed to direct sunlight for long periods
Depending on the light source you are using, the
case of the watch may become quite hot during
charging. Take care to guard against burn injury
after charging.
To charge the battery
Point the solar cell (face) of the watch at a light source to charge
the battery.
Remember that even a partial blockage of the solar cell reduces
charging efficiency.
Example: Positioning the watch
Solar Cell
The illustration shows the resin band model.
Charging Guide
Starting from a full charge, the watch
should be able to continue operating
for about four months without further
charging under the conditions
described below.
Daily Use
Illumination: 1.5 second
Alarm: 10 seconds
Signal reception: 1
Making sure the watch is regularly
exposed to light ensures stable
operation.
Charge Times Required to Advance to a Higher Level
Exposure Level
(Brightness)
Outdoor Sunlight
(50,000 lux)
Sunlight Through a
Window (10,000 lux)
Daylight Through a Window on
an Overcast Day (5,000 lux)
Indoor Fluorescent
Lighting (500 lux)
Approximate Exposure Time
Timekeeping Restored
Full Charge
– – –
– – –
1 hour
2 hours
3 hours
30 hours
12 hours
61 hours
Note that the above charging times are for reference only. Actual
charging time depends on a variety of environmental factors.
The power supply of this watch uses a solar cell to generate electrical power, which is stored by a rechargeable battery. Using or storing
the watch where it is not regularly exposed to light, or allowing it to be blocked from light by your sleeve for long periods as you are
wearing it can cause the power of the rechargeable battery to run down.
A low battery can cause timekeeping to stop, and can also cause time and alarm settings to be lost.
Face illumination or alarm operation can cause hand movement to stop due to the sudden temporary drop in battery power. This does not
indicate malfunction, and normal operation will resume when the watch is exposed to light. Though hand movement stops, timekeeping
continues internally, and the hands will be adjusted to the correct setting when normal operation returns.
Checking the Battery Level
Low battery power is indicated when the the second hand starts to jump at two-second intervals.
Jumps two seconds1-second movement
Indicates date home position.
Normal Low Power Alert Timekeeping Disabled
Battery level
drops due to
insufficient
charging.
Battery level
drops further
due to
insufficient
charging.
Hands
stop at 12
o’clock.
If 2-second hand movement is being performed when the current time reaches midnight, the date indicator will change to the home
position indicator ( ). If battery power drops to the next lower level, and the hands will stop at 12 o’clock.
Even after the battery drops to the level that timekeeping becomes disabled, you will be able to resume normal operation by charging the
battery.
After timekeeping becomes disabled, the hands will move to the current time after the battery is recharged sufficiently.
Keep the watch exposed to light until normal operation returns.
Important!
The following
operations are disabled
during 2-second hand
movement.
Auto and manual
calibration signal
reception
Face illumination
Alarm
Power Supply
To ensure stable operation, be sure to allow the watch to be exposed to light as
much as possible.
Required Daily Charging Time
The following is the daily
amount of charging required
each day to support the
operations under “Daily Use”.
Exposure Level
(Brightness)
Outdoor Sunlight
(50,000 lux)
6 minutes
30 minutes
48 minutes
8 hours
Sunlight Through a
Window (10,000 lux)
Daylight Through
a Window on an
Overcast Day
(5,000 lux)
Indoor Fluorescent
Lighting (500 lux)
Approximate
Exposure
Time
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Casio 3721 Specifications

General IconGeneral
Model3721
CategoryWatch
TypeDigital
DisplayLCD
Water Resistance50 meters
AlarmYes
CalendarYes

Summary

Modes and Hand Movement

Timekeeping Mode

Basic watch operation and button functions.

Receive Result Mode

Check status of the last signal reception.

Alarm Mode

Setting the alarm time and toggling it on/off.

Home Position Adjustment Mode

Adjusting analog hands to their correct home positions.

Power Supply and Charging

Power Supply Overview

Explains solar cell, rechargeable battery, and low battery issues.

Checking Battery Level

How low battery is indicated by second hand movement.

Charging Precautions

Warnings about charging in hot environments.

How to Charge the Battery

Instructions for charging via the solar cell.

Charging Guide

Daily charging needs and charge time estimates.

Face Illumination

Manual Face Illumination

Activating the watch light by pressing the A button.

Auto Light Switch Operation

How the light activates automatically when angled in darkness.

Auto Light Precautions

Warnings about battery drain and unintended activation.

Radio-controlled Watch Functionality

Positioning for Reception

How to position the watch for optimal auto light activation.

How Radio-controlled Watches Work

Explanation of time calibration signal reception.

Reception Factors and Locations

Signal range, factors affecting reception, and ideal locations.

Receiving the Calibration Signal

Auto and Manual Receive

Methods for receiving the time calibration signal.

Positioning for Optimum Reception

Guidance on watch placement for better signal reception.

Time Required for Reception

Duration of a calibration signal receive operation.

Checking Last Signal Receive Result

How to check the outcome of the last signal reception.

Calibration Signal Reception Precautions

Important advice for successful and accurate signal reception.

Using the Alarm

Setting the Alarm Time

Step-by-step procedure to set the desired alarm time.

Setting Alarm Time Direction

Options for setting alarm time clockwise or counterclockwise.

Turning Alarm On or Off

How to toggle the alarm function between ON and OFF.

Stopping the Alarm

Procedure to stop the alarm beeper when it sounds.

Adjusting the Home Positions

Entering Home Position Adjustment Mode

How to access the mode for hand and date adjustment.

Adjusting Second Hand Home Position

Procedure to set the home position for the second hand.

Adjusting Hour and Minute Hand Home Positions

Steps to set the home positions for hour and minute hands.

Adjusting Date Home Position

Procedure to set the home position for the date indicator.

Exiting Home Position Adjustment

Returning to Timekeeping Mode after adjustments.

Adjusting the Time Manually

Manually Resetting Second Hand

Procedure to reset the second hand to the top of the minute.

Manually Setting Hour and Minute

Steps to adjust the hour and minute hands manually.

Setting Time Direction

Options for setting time clockwise or counterclockwise.

Adjusting the Date

Procedure to manually set the date.

Adjusting Month and Year

Steps for manually setting the month and year.

Power Saving

Sleep State Overview

Explanation of how the watch enters a sleep state in darkness.

Sleep Level 1 and 2

Details on the different levels of power saving states.

Recovering from Sleep State

How to wake the watch from its sleep state.

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