Reliable Range: Communication range up to 300m (distance from sensors to receiver/alarm/chime) and detection range up to 8m (distance from sensors to detected objects). Adjustable volume and mode: the alarm in receiver has ringer volume up to 100dB with 3 alert choices (chime high volume/low volume/alarm) and 3 modes (sound/LED flash/sound and LED flash). Multiple uses : perfect for keeping you informed with a little warning before guests or intruders arrive. You can expand your home alarm system with up to 5 sensors to 1 receiver for your demand. Installation Tips: Keep the PIR sensors in a clear path to the receiver and don't place the sensors there where the wind will move them or change their sensing angles, so you can get the best performance. Power Source: You can use 3 x 1.5V Type-C batteries (not included) or an AC adapter ( not included) for the receiver, and 3 AAA batteries (not included) for the sensors. Never use type C batteries and AC adapter at the same time.