This Angelcare Movement Sensor with Sound Monitor (AC401) detects your little one's slightest movements. The sensor has a wide variety of optional features so you can customize it to suit your personal needs. The baby movement sensor offers peace of mind so you know your baby is safe and secure. With a range of up to 820' and eight channels to minimize interference, the monitor offers continuous or voice-activated sound transmission. It sounds an alarm when no movement is detected for 20 seconds. For convenience, the monitor features a temperature display, as well as sound and movement indicator lights.