Introduction
This manual provides detailed instructions for the MOSTRUST Digital Chess Timer Professional, Model YS-902. This versatile 3-in-1 multifunction portable clock is designed for various board games, including International Chess, Chinese Chess, and Go. It features countdown/count-up timing, an alarm function, and a large, clear display for easy readability.

Image: The MOSTRUST Digital Chess Timer Professional, featuring a black body with white buttons and a digital display.
Setup
1. Battery Installation
The chess timer requires two (2) AA batteries. These are typically included with your purchase. To install or replace batteries:
- Locate the battery compartment on the underside of the timer.
- Open the battery compartment cover.
- Insert two AA batteries, ensuring correct polarity (+/-).
- Close the battery compartment cover securely.

Image: The MOSTRUST Digital Chess Timer packaging, showing the timer, its box, and two AA batteries.
2. Power On/Off and Mute Function
On the back of the timer, you will find a switch for power and mute control:
- Slide the switch to the ON position to power on the device.
- Slide the switch to the OFF position to power off the device.
- The switch also includes a MUTE option to silence the alarm.
Operating Instructions
The following video demonstrates the timer's features, including the ON/OFF/Mute switch, button functions, choosing timing modes, and setting the basic timing mode.
Video: A demonstration of the MOSTRUST Digital Chess Clock Timer's features, including the mute function, button overview, selecting timing modes, and setting the basic timing mode.
1. Button Functions
The timer features four main function buttons on the front panel:
- Up Button (▲): Used to increase values during time setting.
- Set/Reset/Confirm Button (Power Symbol): Used to enter setting mode, confirm selections, and reset settings.
- Start/Stop/Next Button (Play/Pause Symbol): Used to start or stop the timer, and to move to the next setting parameter.
- Down Button (▼): Used to decrease values during time setting.

Image: The digital chess timer displaying "0:10:00" on both sides, with labels for "basic", "bonus", and "delay" timing modes, and the four function buttons below the display.
2. Choosing a Timing Mode
The MOSTRUST Digital Chess Timer offers three timing modes: Basic, Bonus, and Delay. To select a mode (as shown in the video from 0:30):
- Ensure the timer is powered on.
- Use the Up (▲) and Down (▼) buttons to cycle through the available timing modes displayed on the screen.
- Once your desired mode (e.g., Basic) is highlighted or selected, press the Set/Reset/Confirm button to confirm your choice.
3. Setting the Basic Timing Mode
After selecting the Basic Timing Mode, follow these steps to set the time (as shown in the video from 0:46):
- Press the Set/Reset/Confirm button to enter time setting mode. The hour digits will begin to flash.
- Use the Up (▲) and Down (▼) buttons to adjust the hour.
- Press the Start/Stop/Next button to move to the minute setting.
- Use the Up (▲) and Down (▼) buttons to adjust the minutes.
- Press the Start/Stop/Next button to move to the second setting.
- Use the Up (▲) and Down (▼) buttons to adjust the seconds.
- Once all time parameters are set for the first player, the second player's time will automatically mirror the first player's settings.
- Press the Set/Reset/Confirm button to save the settings and exit the setting mode.
Note: For detailed instructions on setting Bonus and Delay modes, please refer to the specific mode's section in the full manual (if available) or experiment with the buttons following a similar logic.
4. Starting and Stopping the Game
Once the timing mode and time are set:
- Press the Start/Stop/Next button to begin the game. The timer for the active player will start counting down.
- Players press their respective side's large white button after making a move to stop their timer and start the opponent's timer.
- To pause the game, press the Start/Stop/Next button again. Press it once more to resume.
- When a player's time runs out, the timer will alarm (if not muted).

Image: Two circular insets showing individuals engaged in chess games, one in a teaching/training environment and another in a professional competition, illustrating the timer's use.
Maintenance
1. Cleaning
- Wipe the timer with a soft, dry cloth.
- Do not use abrasive cleaners or solvents, as these may damage the surface.
2. Storage
- Store the timer in a cool, dry place away from direct sunlight and extreme temperatures.
- If storing for an extended period, remove the batteries to prevent leakage.
Troubleshooting
| Problem | Solution |
|---|---|
| Timer does not power on. |
|
| Display is dim or flickering. |
|
| Alarm does not sound. |
|
| Cannot set the time or mode. |
|
Specifications
| Feature | Detail |
|---|---|
| Brand | MOSTRUST |
| Model | YS-902 |
| Color | Black |
| Display Type | Digital |
| Power Source | 2 AA Batteries (included) |
| Product Dimensions (L x W x H) | 5.5 inches (14 cm) x 3.5 inches (8.9 cm) x 1.8 inches (4.6 cm) |
| Item Weight | 6.9 ounces (approx. 195 grams) |
| Material | Acrylonitrile Butadiene Styrene (Plastic) |
| Special Feature | Adjustable Volume (via Mute switch) |
| Alarm Clock | Yes |
| Timing Modes | Basic, Bonus, Delay (3-in-1 Multifunction) |

Image: The MOSTRUST Digital Chess Timer with its dimensions (5.5 inches / 14 cm length, 3.5 inches / 8.9 cm width, 1.8 inches / 4.6 cm height) clearly labeled.
Warranty Information
This MOSTRUST Digital Chess Timer comes with a Limited Warranty. For specific terms and conditions, please refer to the warranty card included in the product packaging or contact customer support.
Support
For further assistance, technical support, or inquiries regarding your MOSTRUST Digital Chess Timer (Model YS-902), please contact the manufacturer, TIANXIAYI, or refer to the official MOSTRUST website for contact details.





