433MHz Wireless Door/Window Magnetic Sensor For GSM Home Security Alarm Systems Easy to install--just peel and stick Built-in omnidirectional antenna - The door/windows alarm with built-in antenna to strengthen the signal, make it more sensitive Can't work standalone - The door detector work with home alarm system,use as alarm accessories. Low-voltage reminder function - When wireless door sensor is in low voltage, it will flash light all the time to remind user change the batteries. Magnetic sensor switch detects entry protecting your home or office. Superior circuit design, High-performance and low power consumption.