This product is a wireless multifunction intercom system telephone, able to support 1 to 999 users in one system, two way intercom, also hands-free intercom. The device can use 18650 battery, easy loading and displays rich content and clear function instructions. The technology adopts the 433MHz frequency and has good wall-penetrating performance. It’s wireless communication distance is up to about 1000 meters in the open area.(without any obstacle).