... 2monitor function 3clear voice and video 4good stability>300m wireless video door bell&phone, video intercom ... security color camera, two-way intercom, door bell, and door release in one easy to set up ... system. The Door bell uses 2.4g digital wireless technology, providing a secure and private signal . ... transmisssion3).Full-duplex hands-free call, clear audio and video .4).Visiting key wake up call, ...