MAGNETIC: The alarms operate through the magnetism between the alarm transmitter and magnet receiver. The 90 dB siren activates when an equipped door or window is opened (trigger gap: more than 10 mm). EASY: The alarm sensor and magnetic receiver come with adhesive tape. No tools are required; simply attach them to a door frame. TECHNICAL DETAILS: Transmitter dimensions: 9x3x2cm; magnet receiver: 5x1x1.5cm | Battery: 2x AAA 1.5V per alarm (included) | Volume: 90dB MANY USES: Enhance the security of your front door, terrace, or balcony, as well as your bedroom or children's room - the set of 4 alarms and receivers offers versatility. Uses: it can be mounted on doors and windows with switches. When the switch is activated, an audible alarm will sound if the doors and windows are opened. Activate the alarm switch when you sleep at night or when you are away from home or the office for added safety and theft prevention. White color. Number of pieces delivered: 4 pieces. NOTE: Please ensure that your apartment or house is suitable for setting up the security system to avoid accidental triggering.