Introduction
This manual provides detailed instructions for the proper use and maintenance of your Casio STL-S110H-1ACF Tough Solar Runner Digital Watch. This timepiece is designed for active individuals, featuring solar power, multiple digital functions, and a durable resin construction.

Figure 1: Casio STL-S110H-1ACF Tough Solar Runner Digital Watch. This image displays the watch's digital face, resin case, and band, highlighting its robust design.
Setup
1. Initial Charging
Your watch is equipped with Tough Solar technology, which converts light into electrical energy. Before initial use, or if the display is blank, expose the watch to bright light for several hours. Ensure the watch face is directly exposed to light for efficient charging.
- Charging Environment: Place the watch near a window or under a strong artificial light source. Avoid extreme heat.
- Battery Level Indicator: The watch features a battery level indicator. Ensure it shows a sufficient charge before setting the time and using functions.
2. Setting the Time and Date
- In the Timekeeping Mode, press and hold the ADJUST button (usually top-left) until the city code starts to flash. This indicates the setting mode.
- Use the MODE button (usually bottom-left) to cycle through the settings: City Code → DST (Daylight Saving Time) → 12/24-hour format → Seconds → Hour → Minute → Year → Month → Day.
- Use the SEARCH or FORWARD/REVERSE buttons (usually top-right and bottom-right) to change the flashing value.
- Once all settings are correct, press the ADJUST button again to exit the setting mode.
Operating Instructions
Your Casio STL-S110H-1ACF watch offers various modes and functions. Use the MODE button to navigate between them.
1. Timekeeping Mode
This is the default mode, displaying the current time, day, and date. From this mode, you can activate the LED light.
- LED Light: Press the LIGHT button (usually top-right) to illuminate the display. The light features an after-glow function.
2. Stopwatch Mode
The stopwatch measures elapsed time, split times, and two finishes. It has a capacity of 1/100-second for 100 hours.
- Enter Stopwatch Mode using the MODE button.
- Press the START/STOP button (usually bottom-right) to start timing.
- Press START/STOP again to stop.
- Press the RESET button (usually top-right) to reset to zero.
- For split times, press SPLIT (usually top-right) while timing, then START/STOP to stop, and RESET to clear.
3. Countdown Timer Mode
The watch includes two independent countdown timers, useful for interval training or specific tasks.
- Enter Countdown Timer Mode using the MODE button.
- Press and hold the ADJUST button to enter setting mode.
- Use the MODE button to select which timer (T1 or T2) to set, and then to cycle through hours, minutes, and seconds.
- Use the SEARCH or FORWARD/REVERSE buttons to change the values.
- Press ADJUST to exit setting mode.
- Press START/STOP to start or stop the countdown.
4. World Time Mode
View the current time in 48 cities (29 time zones) around the world.
- Enter World Time Mode using the MODE button.
- Use the SEARCH or FORWARD/REVERSE buttons to scroll through city codes.
- To swap your Home City time with the World Time City, press the ADJUST and SEARCH buttons simultaneously.
5. Alarm Mode
Set up to five daily alarms and an hourly time signal.
- Enter Alarm Mode using the MODE button.
- Use the SEARCH or FORWARD/REVERSE buttons to select an alarm (AL1 to AL5) or the Hourly Time Signal (SIG).
- Press and hold the ADJUST button to enter alarm setting mode.
- Use the MODE button to select hour or minute.
- Use the SEARCH or FORWARD/REVERSE buttons to change the values.
- Press ADJUST to exit setting mode.
- To turn an alarm or the hourly time signal on/off, select it and press the START/STOP button.
Maintenance
1. Cleaning
- Wipe the watch with a soft, dry cloth to remove dirt and moisture.
- For stubborn dirt, use a soft cloth dampened with water and a mild neutral detergent. Avoid harsh chemicals.
- Clean the resin band regularly to prevent skin irritation and maintain its appearance.
2. Solar Charging Care
- Ensure the watch face is regularly exposed to light to maintain optimal battery charge.
- Avoid prolonged storage in dark places, as this can lead to battery depletion.
- Do not expose the watch to extremely high temperatures during charging (e.g., on a car dashboard in direct sunlight).
3. Water Resistance
This watch is designed for daily use and can withstand splashes or brief immersion in water. However, it is not suitable for diving or prolonged underwater use. Do not operate buttons while the watch is wet.
Troubleshooting
- Display is blank or dim: The watch battery may be low. Expose the watch to bright light for several hours to recharge.
- Time is incorrect: Re-adjust the time and date settings as described in the "Setting the Time and Date" section. Ensure the correct home city and DST settings are selected.
- Buttons are unresponsive: This could indicate a very low battery level. Charge the watch fully. If the issue persists, contact customer support.
- Watch stops functioning after exposure to water: Ensure buttons were not pressed underwater. Allow the watch to dry completely. If issues persist, seek professional service.
Specifications
| Model Number | STLS110H-1A |
| Power Source | Tough Solar (Solar rechargeable battery) |
| Battery Life (Full Charge) | Approx. 11 months (without further exposure to light) |
| Case Material | Resin |
| Band Material | Resin |
| Dial Window Material | Mineral |
| Case Dimensions | 49 mm (diameter) |
| Product Dimensions | 5.26 x 5.46 x 1.4 cm |
| Weight | 54.43 g |
| Water Resistance | General daily use (splash resistant) |
| Functions | LED light with after-glow, 5 daily alarms, hourly time signal, world time (48 cities), stopwatch (1/100-second, 100-hour capacity), 2 countdown timers, auto-calendar. |
Warranty and Support
Your Casio watch is covered by a manufacturer's warranty. Please refer to the warranty card included with your purchase for specific terms and conditions, including warranty period and coverage details. For technical support, service, or inquiries regarding your watch, please contact Casio customer service through their official website or the contact information provided in your warranty documentation.
For further assistance, visit the official Casio support website: www.casio.com/support





