CASIO EF-521 Watch User Manual

❗❗❗ Important Information to Read First

This section contains crucial information regarding the operation and care of your CASIO watch.

Battery

If the display becomes dim or the backlight does not function, the battery needs replacement. Please visit an authorized CASIO dealer or distributor for replacement. The battery included with your watch is a test battery and its lifespan may be shorter than a standard battery.

Water Resistance

Your watch is classified by water resistance rating, from I to V. Please refer to the table below to understand the appropriate usage for your watch's rating.

Notes:

• Rating I: The watch is not water resistant. Avoid all contact with moisture.
• Ratings III, IV, V: If the watch is exposed to salt water, rinse it thoroughly with fresh water and dry it.
• Rating V: Suitable for scuba diving (except for depths requiring a helium-oxygen mixture).

❗❗❗ For all watches, it is prohibited to:

• Press buttons underwater.
• Adjust the crown underwater.
• Unscrew the crown underwater.

❗❗❗ Important Note: Some water-resistant watches feature leather straps. Do not wear these watches while swimming or engaging in any activity where the strap may be submerged in water.

Care for Your Watch

• The rubber gasket that seals the watch from water and dust should be replaced every 2-3 years.
• If water enters the watch, have it inspected immediately by an authorized CASIO dealer or distributor.
• Avoid exposing the watch to extreme high or low temperatures.
• While designed for normal use, avoid rough handling and dropping the watch.
• Do not fasten the watch strap too tightly. A finger should fit between your wrist and the strap.
• To clean the watch and strap, use a dry, soft cloth or a soft cloth dampened with a mild neutral detergent solution.
• Never use volatile agents such as gasoline, thinners, or spray cleaners.
• When not using your watch, store it in a dry place.
• Avoid contact with gasoline, cleaning solvents, aerosol sprays, adhesives, paint, etc. Chemical reactions from these materials can damage gaskets, the case, and the watch's finish.
• Some models have silk-screened designs on the strap. Be careful when cleaning such straps to avoid damaging the designs.

For Watches with Polymer Straps...

• A white powdery substance may appear on the strap. This substance is harmless to skin or clothing and can be easily removed by wiping with a soft cloth.
• Exposure of the polymer strap to sweat or moisture, or storage in high humidity conditions, can lead to damage, tearing, or cracking. To ensure the longevity of the polymer strap, wipe it clean of dirt and water with a soft cloth as often as possible.

For Watches with Fluorescent Cases and Straps...

• Prolonged exposure to direct sunlight can gradually cause the fluorescent color to fade.
• Prolonged contact with moisture can cause the fluorescent color to gradually fade. If moisture gets onto the watch surface, wipe it off as soon as possible.
• Prolonged contact with a wet surface can lead to discoloration of the fluorescent color. Be mindful of moisture on the fluorescent surface and avoid contact with other surfaces.
• Friction of a surface with applied fluorescent paint against another surface may transfer the fluorescent paint to that other surface.

Disclaimer

CASIO COMPUTER CO., LTD. is not responsible for any damages that may arise from the use of this watch, nor does it accept claims from third parties.

Watch Components Diagram

The watch features the following components:

• Hour Hand: Indicates the hour.
• Minute Hand: Indicates the minute.
• Second Hand: Indicates the second.
• Crown: Used for setting time, date, and day. It has multiple positions:
  • Normal Position: The standard position when not setting anything.
  • 1st Click: Pull the crown out to this position to set the date and day of the week.
  • 2nd Click: Pull the crown out to this position to set the current time. The second hand stops when pulled to this position.
• Date Display: Shows the current date.
• Day of Week Display: Shows the current day of the week.

Setting the Current Time

1. Pull the crown out to the 2nd click. The second hand will stop.
2. Turn the crown to set the hour and minute hands to the current time.
3. Push the crown back to its normal position to complete the setting.

Setting the Current Day

1. Pull the crown out to the 1st click.
2. Turn the crown clockwise to set the current day.
3. Push the crown back to its normal position.

Note: Do not set the day between 9 PM and 1 AM, as this may cause the day to not change correctly.

Setting the Day of the Week

1. Pull the crown out to the 1st click.
2. Turn the crown counter-clockwise to set the current day of the week.
3. Push the crown back to its normal position.

Note: Do not set the day of the week between 11 PM and 2 AM, as this may cause the day of the week to not change correctly.

Stopwatch Usage

This watch allows you to measure elapsed time up to 29 minutes and 59 seconds.

• To start measurements, press button "A".
• To stop measurements, press button "A" again.
• To reset the measured values, press button "B".

You can continue measurements by pressing button "A" again after stopping.

Some watches are equipped with a rotating bezel. To measure elapsed time, align the bezel marker with the minute hand. After the elapsed time, the minute hand will indicate the measured duration on the bezel.

Stopwatch Synchronization

This procedure ensures the stopwatch hands (second and minute) are correctly zeroed.

1. Press button "B" to reset the stopwatch to zero and check the position of the stopwatch second and minute hands.
2. Press button "A" to move the stopwatch second and minute hands.
3. Press button "A" to move the stopwatch second hand in one-second increments. Holding down button "A" allows for faster movement.
4. Press button "B" to move the stopwatch minute hand to the correct position.
5. After synchronization, push the crown back to its normal position.

Technical Specifications

• Accuracy: ±20 seconds per month at normal temperatures.
• Indicators: Three analog hands (hour, minute, and stopwatch second); three sub-dials (stopwatch 1/10 second, stopwatch minute, 24-hour/day indicator); date.
• Stopwatch Functions: Measures elapsed time up to 29 minutes and 59 seconds, in 1-second increments. Measurement mode: elapsed time.
• Battery: One silver-oxide battery (Type SR626SW).
• Battery Life: Approximately 2 years on an SR626SW battery (assuming stopwatch is used once per hour).

Product Information