Upgrade your home and office security with BlackT Electrotech (BT51D) 120dB 4in1 Wireless Door and Window Alarm Sensor. Designed for modern families, offices, and shops, this wireless calling bell and alarm system provides a reliable solution for preventing unauthorized access. With its powerful 120dB siren, the sensor instantly alerts you when a door or window is opened, acting as both a door alarm security system and a wireless door bell without wire. Whether you need an office cabin bell, an entry chime for your shop, or a protective alarm for your flat, this 4-in-1 device is the smart choice. Installation is quick and hassle-free—no wire, no drilling required. Simply peel and stick the magnetic strip and alarm unit, and you’re secured in seconds. Compact yet powerful, it fits seamlessly into any home or workspace while offering maximum protection. Protect your loved ones and property with a versatile wireless security sensor trusted for homes, offices, cabins, and commercial spaces. ?? Product Specifications Brand & Model: BlackT Electrotech BT51D Functionality: 4-in-1 Wireless Door Bell, Window Alarm, Entry Alert, Security Siren Alarm Sound Level: 120dB – loud enough to alert instantly Installation: Easy peel-and-stick setup, no wiring required Application: Suitable for home, office cabins, shops, and property security Power Source: Battery-operated (long-lasting performance) Design: Compact, lightweight, and portable for versatile use Use Case: Works as wireless calling bell, office cabin bell, door alarm security system, and window entry sensor