120° Sensing Angle: Adopt imported infrared probe, universal rotation 120° sensing area, sensing distance 3‑7 meters, sensitive and . 4 Gears Volume Adjustment: Farewell embarrassed of inaudibilit. With intelligent volume adjustment, don't worry about inaudible. (Note: It is recommended to adjust the volume to 1‑2 for daily use.) 433MHzH Frequency Modulation Signal Scheme: The transmission of strong signal penetration is more than 200 meters, to meet all kinds of life needs. Protective: During the day and night, when there is no one at home, someone opens the door and the doorbell rings to trigger the burglar alarm, protecting the safety of family and property. One Button Mute: To avoid disturbing the elderly and children. Can choose mute mode, only flashing lights without ringing the bell to avoid waking the sleeping baby or the elderly.