CELT21 - Smartphone Sunstech - Free user manual and instructions
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| Product Type | Smartphone |
| Brand | Sunstech |
| Model | CELT21 |
| Display Size | 5.5 inches |
| Display Resolution | 1280 x 720 pixels (HD) |
| Processor | Quad-core 1.3 GHz |
| RAM | 2 GB |
| Internal Storage | 16 GB |
| Expandable Storage | microSD up to 128 GB |
| Rear Camera | 8 MP |
| Front Camera | 5 MP |
| Battery Capacity | 3000 mAh |
| Operating System | Android (Go Edition compatible) |
| Connectivity | 4G LTE, Wi-Fi 802.11 b/g/n, Bluetooth 4.2 |
| SIM Support | Dual SIM (Nano-SIM) |
| GPS | Yes, with A-GPS |
| Sensors | Accelerometer, proximity, ambient light |
| Dimensions | 155 x 78 x 9 mm |
| Weight | 180 g |
| Charging Port | Micro USB |
| Audio Jack | 3.5 mm stereo |
| Maintenance & Cleaning | Use a soft dry cloth; avoid liquids and abrasive cleaners |
| Safety Warning | Use only certified chargers and cables; avoid extreme temperatures |
| Spare Parts & Repairability | Battery and display replaceable by authorized service centers |
Frequently Asked Questions - CELT21 Sunstech
How do I insert the SIM and memory card?
Locate the SIM tray on the side of the phone. Use the provided ejector pin or a small paperclip to push into the tray hole. Once ejected, place the Nano-SIM cards and microSD card (if any) into the tray, then reinsert it firmly.
How can I extend the battery life of my CELT21?
Reduce screen brightness, turn off Bluetooth and GPS when not needed, close background apps, and activate Battery Saver mode from Settings > Battery. Also disable unused connectivity like Wi-Fi when out of range.
What should I do if the screen freezes or is unresponsive?
Press and hold the Power button for about 10 seconds to force a restart. If the problem persists, boot into Safe Mode by holding power and pressing 'Restart' > 'Safe Mode' to check if a third-party app is causing the issue.
How do I take a screenshot on the Sunstech CELT21?
Press the Power button and Volume Down simultaneously for a second. You will see a screenshot animation. Find the screenshot in your gallery or in the 'Screenshots' folder.
Is the CELT21 compatible with all 4G networks?
The CELT21 supports 4G LTE on common bands (e.g., B3, B7, B20). However, compatibility may vary by region and carrier. Check with your network provider for full band support before purchasing.
How do I free up storage space?
Go to Settings > Storage and clear cached data from apps. Uninstall unused apps, transfer photos/videos to a microSD card, and use the Files app to remove duplicate or large files.
Can I expand the storage beyond 128 GB?
The official maximum supported microSD capacity is 128 GB. Using higher-capacity cards may cause compatibility or formatting issues. It's recommended to use a class 10 card from a reputable brand.
How do I perform a factory reset?
Back up your data first. Go to Settings > System > Reset > Factory data reset. Confirm the action. The phone will erase all data and restore to original settings. This can solve most software issues.
Why is the phone charging slowly?
Check that you are using the original charger and cable. Dust or lint in the charging port can reduce contact; clean it gently with a toothpick. Also, avoid charging while using heavy apps, as this slows charging.
How do I update the Android system?
Go to Settings > System > Software update and tap 'Check for updates'. Download and install any available updates. Ensure you have a stable Wi-Fi connection and at least 50% battery before updating.
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USER MANUAL CELT21 Sunstech
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Product information
Brand : Sunstech
Model : CELT21
Category : Smartphone